nvhrbiblio.nl World/1920/Wireless... · PRECISION WIRELESS APPARATUS PATENT HIGH -RESISTANCE...

Price 9d. Net. FEBRUARY, 1920.

WIRELESSWORLD

ANTI -SULPHURIC" ENAMEL GRIFFITHS BROS. & Co. (London) Ltd.RESISTS ACID FUMES, Etc. " MACKS ROAD, BERMONDSEY, S.E. 16

PRECISION WIRELESS APPARATUSPATENT HIGH -RESISTANCE TELE-PHONE RECEIVERS 8,000 ohms.These are fitted with safety sparkgap and tested up to 500 volts A.C.

TELEPHONE AND INTERVALVETRANSFORMERS.

TRIODE VALVE GENERATORS forA.C. bridge testing.

PRECISION AND STANDARDMEASURING EQUIPMENTS for high -frequency and wireless determinations. COUPLING COILS, VALVES, ETC.

NEW LIST "W " NOW READY.

H. W. SULLIVAN,

LONG SCALE VARIABLE AIRCONDENSERS with 360° scale, otherpatterns with Micrometer Adjustment,capacities : 1 20-10,000 micro-microfarads.

ROTARY PATTERN FILAMENTRESISTANCES, and Grid PotentialRegulators, Continuously adjustable.

NON -REACTIVE RESISTANCES forA.0 and H.F. Measurements.

WINCHESTER HOUSE,LONDON, E.C.2., ENGL AND

WORKS: "LIVERPOOL HOUSE," MIDDLESEX STREET, LONDON, E. ITelegrams: "Deadbeat. Avenue, London.** Telephone: Office-London Wall 3518. Works - Avenue 4871

THE BRITISH SCHOOL.''TELEGRAPHYff

179, CLAPHAM RI?LONDON. SW

EXPERT TRAINING FOR YOUNG GENTLEMEN (15-25) IN INLAND. CABLE & WIRELESSTELEGRAPHY. Good Appointments are open to our students as soon as qualified, the demand for Skilled Operatorsin all Services being greater than the supply. Special Short Course suitable for men wishing to obtain GovernmentCertificate and enter the service of the Marconi Co. At several recent Government Exams. all candidates obtained1st Class Government Certificate. No Branches or Postal Tuition. Fees moderate. Recognised by the War Office,

Admiralty. Wireless Telegraph and Cable Companies.

WRITE FOR PROSPECTUS. A. W. WARD (Manager). 'Phone : BRIXTON 215

February, 192o. Please mention the Tireless World

THE WIRELESS WORLD (A dv; rtisenzents;

E.C.C.DYNAMOS, MOTORS,MOTOR=GENERATORS,ROTARY CONVERTERS,BOOSTERS &SWITCHGEAR.

125 Kw. Singlephase to D.C. Induction Motor - Generator 575 r . p . m.

THE ELECTRIC CONSTRUCTIONCOMPANY, LIMITED.

HEAD OFFICE : Dashwood House, 9, New Broad Street, London, E.C. 2.Telephone Nos. 10920 Central & 2671 Lordon Wall.

WORKS : Bushbury, Wolverhampton. Telephone Nos. 75 & 430 Wolverhampton.

Glasgow Office : 166, St. Vincent Street. Telephone No. 1044 Central.

Sole A gent for Lancashire : Mr. R. M1LLETT, 30. Cross Street. Manchester.Telephone No. 7772 City.

Bel fast Office: Scottish Temperance Buildings Donegal) Square.Telephone No. 2846 Belfast.

Agent for Belgium Mr. FERNARD ESPIR. 3. East India Avenue. LeadenhallStreet, London, E.C.3 ; and at 33. Rue Zarezo. Brussels.

Febraa, y, 192o. iii Please mention the Wireless World

lul

THE -WIRELESS WORLD (Advertisements)

rust

GAMAGESTHE PIONEER SPECIALISTS IN, ANDMAKERS of, WIRELESS INSTRUMENTS

et,

t

Valve Panel with filament resistance,mounted on polished mahoganycabinet 6" x x I ; Ebonite topI" thick. Engraved and filled inwhite. Price ... 30/ -Three electrode valve for reception ;Price ... 2216

HOLBORN,LONDON, E.C. 1

Rotary VariableAir Condenser.(Faraday House

Calibration.)This instrument isone of the neatest and withal an exceedingly efficient piece ofapparatus. It has 16 fixed and 15 moving vanes, the capacityranging from 1 Micro Microfarad to 716 Micro MicrofaradThe top plate is of turned and polished ebonite with engravedscale finished white. The most efficient and best constructedsmall condenser on the market ... ... Price 35 -

CHAS. BAKERAND CO.'S STORES, LTDLARGEST OUTFITTERS IN LONDON

High-class TailoringAT MODERATE PRICES

INDIAN COLONIAL &FOREIGN OUTFITS

egulation UniformsHead Depot - 271-274 HIGH HOLBORNCity Branch - 41, 43, LUDGATE HILL37-140 Tottenham Court Road, 256 Edgware Road, &c

Please mention the Wireless World

THE WIRELESS WORLD (Advertisements)

0 v

SEND

ENQUIRI

OPENS AWMANCH TER

February, 192o. v Please mention the Wireless TV orld


Telephone:2168 Central

Telegrams :" Britannia. London"

BRITANNIA RUBBER ANDKAMPTULICON CO., LTD.

7 NEWGATE ST.LONDON, E.C.

EBONITE & VULCANITETUBES-RODS-SHEETS

WATERPROOF COATSin great variety for all Climates

MECHANICAL RUBBERMATS- HOSE -TUBESSTEAM JOINTING ANDRUBBER COMPOUNDS

TRADE MARK

The WHITECROSSCOMPANY, LIMITED

WARRINGTON ::

Manufacturers of All Descriptions of

WIRE ROPESAND WIRES

February, 192o.

ARE YOU QUALIFIED FOR pTHE JOB YOU SEEK

CONSIDERVMLLYOUR

UTURE.

IF NOT WHY NOT ?WE TEACH BY POSTat ionShipbuilding

Electricity-ShinitigEngineeringIlathentaticsDraughtsmanshipArchitectural DrawingBuilding:ConstructionInternal Combustion

Engines.

Clerk oil Works DutiesStructures in Concreteand Steel

Civil 1, ngineeringHoner InspectingMarine EngineeringWireless TelegroldlYMotor . nginceringStructurl EngineeringSurveying& LevellingAlso ProlessionalCareers for Ladies.

If you are preparing for any exam. ask ouradvice. We specialise in all exams. con-nected with technical subjects, all particularsFREE OF CHARGE.Parents should seek our advice for their sons.If you are interested in any trade, as shownin the forgoing list, we will send you ourFREE BOOKLET. We have helpedthousands to prosperity. We can help YOU.Write for the one you are interested in.

PLEASE SEAT I, YOUR AGE.

THE BENNETT COLLEGEDept. 129 SHEFFIELD. Estab.1900

The most reliable and efficientBatteries for Wireless Work are

STORAGEBATTERIESD.P. Batteries are made to fit almostany size of box. The output of ourWorks runs to hundreds of thousandsof plates yearly.

Write us for particulars

The D. P. BATTERY CO., Ltd.BAKEWELL -- DERBYSHIRE& 11 Victoria St., London, S.W.



INDEX TO ADVERTISERSA, roplane and General Publishing Co., Ltd.Atlantic College of Wireless and Cable

Telegraphy xi:Baker, Chas. and Co. ... ivBennett College ... viBoyd Brr thers. Ltd. ... viiiBriggs, W. and Sons, Ltd. ...Britannia Rubber and Kamptulicon Co. ... viBritish and Foreign Sailors Society... ... viBritish School of Telegraphy, The ... ...2 CoverBurberrys ... viiCallender's Cable and ConstructionCo.,Ltd. ixChloride Electrical Storage Co., Ltd., The xviCity School of Wireless Telegraphy, Ltd.... xxxvCommercial Union Assurance Co., Ltd. ... xxiiCoubl o & Scrutton xxviiCrompton & Co., Ltd. ... xviiiDale & Hollins xxiiDavis & Timmins, Ltd.... xiiD. P. Battery Co., Ltd., The ... viDrapkin & Co., Major ... xvDubilier Condenser Co., Ltd. xiEast London Wireless Telegraph College... ixElectric Construction Co., Ltd., The ... iiiElectromotors LimitedEllis, J. & H. ... xxviiiFisher & Co., Ltd., Eden ... 3 Cover" Flight " xxivFunk & Wagnalls Co. ... xxviiiGamage, A. W., Ltd. ... ivGardner. Lockett & Hinton ...Gee & Co., Ltd. ... saaiiiGeoffrey, Parker & Gregg ... xxxivGraham & Latham, Ltd. ... xxxivGriffiths Bros. & Co. ... r CoverHarveys' xxxviHenley's Telegraph Works Co., Ltd., W.T. xviLondon Telegraph Training College xxxiLongmans, Green & Co. ... xivMackie & Co., W xxxMarconi International Code Co., Ltd. ... x ixMarconi Scientific Co. ... xviMarconi's Wireless Telegraph Co., Ltd. ... xviiMai shall & Co., P. ... xxivMay & Co. ... x viMcGruer Hollow Spar Co., Ltd. xviii" Merchant Shipping Review and Empire

Trade Gazette" xxviiiMica and Micanite Supplies, Lid. xivMiller, Rayner & Haysom, Ltd. ... xxviiMitchells xictMunro, J., & Co., Ltd. ... xxivNalder Bros. & Thompson, Ltd. 3 CoverNorris, Henty & Gardners, Ltd. ... xxviiiNorth British & Mercantile Insurance Co xixNorth-Eastern Schools of Wireless Tele-

graphy xxiNorth Wales Wireless Schools xivOfficine Elettro Meccaniche xxxiOrmiston & Sons. P. ... xxiiPalmer Tyre, Ltd.Paterson. Ltd., J. & M.Pelman Institute, The" Philatelic Magazine"Pinchin, Johnson & Co.. Ltd....Practical Correspondence College ..."Radio Amateur News"Read, F. O., & Co. ...Rentell, S.. & Co., Ltd.... ...Russell & Shaw ...Samuel Bros., Ltd. ...Self & Son ...Simmonds. Bros.. Ltd.... ...Snewin & Sons, Ltd., C. B. N.

xxivxiii

xxxiiixxii

xiixxxiv

axxxivxxiiviii

xxiii... 3 Cover

xxxivSullivan. H. W. 2 CoverTaylor's Typewriter Co."Telegraph & Telephone Journal, The"xxiiUniversity Engineering College ... ixWeston Electrical Instrument Co. ... xxiiiWhitecross Co., Ltd., The viWidnes Foundry 4 CoverWillcox & Co., Ltd., W. H. ...3 CoverWireless Press ia, xxv, xxvi, xxiiiWireless Training College xxiv"Zodiac, The" x x,,

February, 1920.

BURBERRYWeatherproof Naval Kitis made from cloths specially woven andproofed to exclude wet and cold, and toresist the roughest wear and 'tear. At thesame time they ventilate naturally, andare of the finest texture, being equallysuitable for all branches of Marine Service.

NavalCataloguePost Freeon request

CompleteKits in 2to 4 Daysor Readyfor Use

BURBERRY PILOT COAT.An indispensable safeguard, made in BurberryWeatherproof cloth ; cut and tailored by experts

Coats and suits cleaned by Burberrys.Weatherproof Garments re -proofed.Prices on request.

BURBERRYS HONDONAYMARKES .W.1L

8 & 10 Boul. Malesherbes, Paris; also Agentsii Please mention the Wireless World

1


Telegrams-" UNIFORMS, GLASGOW." NOTICETO

Wireless OperatorsDo not be misled into ordering your

UNIFORMSwhere cheapness is the sole recom,mendation. Let " excellence " beyour loadstone. Correct Detail,Superior Workmanship, GenuineGold Lace, Guaranteed Dyes, theseare the things that matter.Our Price Lists and Advice on Application.

BOYD BROTHERS, LTD.,"HOWARD HOUSE,"

51 & 53, JAMAICA ST., GLASGOW.No' connection with any other Firm ofsimilarname. No branches.

'rit.##$$ 4! ,,,W,

, 0800,,,,,,, `'""`v

, ,,'

riovi,i,I) WiliSE 65:40r,.

,

. . a -.V.

...i1L . s 1

,.''''-1 .r''. 1.,

.

GLASGOW'S " NAVAL " STORE.

SAMUELBROTHERS, LTD -NAVAL and MILITARY

OUTFITTERS

REGULATION WIRELESSAND MERCANTILEMARINE UNIFORMS

RELIABLE INDIGO -DYEDCLOTHS AND BESTQUALITY LACES ONLY

USED

PRICE LIST ON APPLICATION

65 & 67, LUDGATE HILL, E.C. 3HONE:CITYWITHIN 3 MINUTES 'BUS RIDE OF MARCONI HOUSE

:And at OXFORD CIRCUS, W.(22 1 & 223, Oxford Si) PHONE4664 MAYFAIR

February, 1920. viii Please mention the Wireless World


LICENSED BY H.M. DAY and EVENING CLASSES.POSTMASTER -GENERAL.

East London Wireless Telegraph CollegeEstablished 172a & 228, Romford Road, Forest Gate, London, E. 7. Write forEstablished 172a

MENin the

WIRELESSSERVICES

desirous of rapid ad-vancement should pre-pare in spare time forone of the followingrecognised

EngineeringQualifications:-

IndividualisedCourses of Pos a

Trainingare provided by

or these and otherprofessional examine-tMns.ELEVEN YEARSOF SUCCESSES.Expert Advice FreeWrite now for NewProspectus No. 8

statingyour requirements, to:

Secretary's Dept..University

Engineering College,3, St. Mark s Crescent,

Regent's Park.London. N.W. 1.

THE WIRELESSWORLD

THE OFFICIAL ORGAN OFTHE WIRELESS SOCIETY OF LONDON

A MAGAZINE DEVOTED TO WIRELESSTELEGRAPHY AND TELEPHONY.

Registered at the G.P.O. for transmission by MagasinePost to Canada and Newfoundland.

CONTENTSTECHNICAL ARTICLES.

PAGEAn Efficient Variable Condenser 63oFlexible Socket for Wireless Receiving

Valves 632Digest of Wireless Literature..636Notes on the Physics of the Thermionic

Valve 638Proceedings of the Wireless Society of

London (The Transmission of Electro-magnetic Waves about the Earth) 651

Aircraft Wireless Section E65

Notes on the Design and Construction ofValve Amplifiers 671

The Construction of Amateur WirelessApparatus 674

Continued on page x.

SEA,LA ND& AIR

THE

AustralianMonthlyJournal ofAVIATION,

RADIO-TELEGRAPHY

& RADIO-TELEPHONY

PRICE - 1 /3POST FREE

Annual 1 ; /-Subscription 1 -/

THEWIRELESS PRESS,

LTD.,

12-13,Henrietta Street,Strand, W.C.2

LESS COSTLY THAN EBONITEbut just as reliable. It is non -hygroscopic, strong and tough, andpossesses exceptional insulating properties. Grades are madewhich can be moulded, machined or tooled for any description ofinsulator. Let us quote you for insulating material.

CALLENDER'S CABLE AND CONSTRUCTION CO., LTD.,Hamilton House, Victoria Embankment, E.C.4

February, 192o. Please mention the Wireless World

THE 11/7RELESS WORLD (Advertisements)

WRITE DEPT. W.W.

TAYLOR'S for TYPEWRITERSEst. 1884. 74, Chancery Lane (Holborn ind) London, W.C.2

And at 92 Queen Street, E.C4BUY, EXCHANGE, REPAIR &ALL MAKES TYPEWRITERSHIRE, SELL

Duplicators, Adding Machines, and Office Furniture. MSS. Copied. Typistssent out. 'Phone Holborn 4810 (4 Lines)

BituminousSolutions &EnamelsTHE WORLD'SRECORD ANTI -CORROSIVESUnequalled forprotecting all struc-tural steelworkf romthe ravages of time

A COATING OF

BRIGGS'LENGTHENSTHE LIFE OFSTEELWORKINDEFINITELY

Send for priceand samples

W. BRIGGS &SONS, LTD.,DUNDEE

CONTENTS-continued

GENERAL ARTICLES.PAGE

The Training of a R.A.F.Wireless Operator 621Personalities in the Wireless World 628Stray Waves 634The Library Table 644Notes of the Month 645Wireless Club Notes 647Aviation Notes 668

MISCELLANEOUS.

The New Patents Act 635Questions and Answers 677

SUBSCRIPTION RATES.-United Kingdom andBritish Empire (outside North America), lls. postfree ; United States. Canada. and Newfoundland,$2.75 per annum, post free; and Europe.frs. 21 per annum, post free.

Single copies. 9d. each, or post free la.

Articles submitted for acceptance by the Editor(which will be paid for on publication) shouldbe addressed to 12-13, Henrietta Street, Strand,

London, W.C. 2No responsibility can be taken for MSS. or Photographssent without stamps to defray cost of return postage.Telegraphic Address "Radionic, Rand, London."

Telephone No.: Gerrard 2807 (2 lines).

ROOFINGSpecialtiesARE THE EM-BODIMENT OF54 YEARS EX-PERIENCE INTHE BITUMEN &ALLIED TRADES

Before buying else-where send to usfor samples & prices

WE KNOW WECAN SUIT YOUWITH BOTH

BRIGGS"THE

BITUMENPEOPLE"

Head Office :-DUNDEEESTABLISHED 1865.

THE AEROPLANE (6d. weekly) MAKESA SPECIAL OFFER TO ITS READERS

Subscribers for 1 year (30s. home, '35s. abroad, post free) have the right to buy a copy of Saundby's"FLYING COLOURS" (20 coloured pictures of a year's work of the R.F.C. on the Western Frontat half price., viz.

The Edition de Luxe published at £2 2s., each copy numbered, for £1 Is.The Popular Edition published at 15s.. net for 7s. 6d.

Saundby's "FLYING COLOURS" is the most beautiful of all aircraft books. £2 1 1 s.

secures a year's subscription and a copy of the Edition de Luxe.

THE AEROPLANE, (W. Dept.) 61 Carey Street, W.C. 2.

X PICl1,1'ration the H.irrl, .

L-_1111111111111111111111111111111!11111111111111111111111111111111111 1111111111111111111111111111111112_-_=

THE

WIRELESS WORLD!No. 83

Vol. VII

7n1111111111111111111111111111111111111111111111111111I

FEBRUARY,1920

11111111i111111111iIIIII111111111111111H11117-:.

The Training of a R.A.F.Wireless Operator.

BY MICHAEL B. EGAN.

ALTHOUGH most of us mightagree that the narrow limitsof our native tongue ren-der it unsuited to the taskof expressing our private

opinions about war in general and theGreat War in particular, few of us willdeny that four years of Zepp raids andration cards made us the recipients ofa liberal education in our own short-comings, both as an Empire and asindividuals. It might truly be saidthat each day of the war brought itsown particular lesson, but, as oftenas not, the supreme exigencies of themoment prevented the immediake ap-plication of newly -revealed methodsowing to the impracticability of upset-ting existing organisations, or the neces-sity for compromising between outputand efficiency-between quantity andquality.

The signing of the Armistice, how-ever, gave the signal for the embodi-ment of those principles and ideas

which the war so clearly emphasizedas vital to our national success in thegreat work of reconstruction, and inthis respect the post-bellum syllabusfor the training of wireless personnelin the Royal Air Force indicates acommendable determination on thepart of our youngest service to availitself fully of the knowledge acquiredunder the tutorship of war.

Everyone is aware that no otherindividual branch of science played soimportant a part in the conduct of thewar as the ever-expanding science ofwireless telegraphy and telephony. Itwas wireless that rendered it possiblefor our generals in the field to discussstrategy with the War Staff at White-hall whilst preliminary operations wereactually in progress. It was wireless thatenabled our Admiralty Staff to pin -pointthe exact position of every British shipon the ocean charts of the world at anymoment of the day or night; and itwas wireless that enabled our wonder -

621

THE WIRELESS WORLD

Flowerdown Wireless Training Cana, Winchester.

ful Aerial Squadrons to flash backswift tidings of their progress as theyhummed their lonely way above theclouds on their perilous midnight ex-cursions over enemy territory. Wire-less was a subtle sixth sense thatnegatived space and established humanintercourse between the Mother Coun-try and the smallest and most remoteand isolated contingent of British forcesin foreign climes.

The Wireless Operator was ubiqui-tous.

From the outset of the war thedemand for trained wireless personnelwas always in excess of the possibilitiesof supply. Wireless operators couldnot be made in a day, nor yet in amonth, nor, indeed, could they be madeto order in any length of time.

There is something peculiarly dis-tinctive about the personality of areal wireless operator that raises himconsiderably above the ordinary leveland relegates him to a class by himself.Good brains and a capacity for steadyapplication represent two very import-ant characteristics in the compositionof an efficient wireless operator, but,

FEBRUill?Y , 192o

although these are two essential factors,they do not in themselves constitutethe ideal wireless operator. The men-tality of the ideal wireless operatormust include a natural and instinctivealertness of mind balanced by a capa-city for the exercise of sustained self-control during periods of unwontedactivity in the world of ether waves.

This pronounced individuality of -

the pukka wireless personality gaineddaily confirmation during the progressof the war, and by instituting a methodof selection which was based on theaccumulated data of war -time experi-ences, the Royal Air Force has aimedat securing the cream of that veritablearmy of young wireless enthusiastswhose ambition urges them to sharethe limitlesi regions of the blue withthe happy feathered things of nature.

Enlistment in the Wireless ranks ofthe R.A.F. is in active progress at themoment. Trained wireless operatorsand mechanics are being engaged forimmediate service and a large numberof vacancies exists for boys of about 16years of age who will undergo a threeyears' course in wireless telegraphy and

622

TRAINING OF A R.A.F.. WIRELESS OPERATOR.telephony before being graded as Lead-ing Aircraftsmen in the capacity of wire-less Mechanic -Operators. Successfulcandidature for these vacancies involvesa good standard of health, a willingnessto engage for 8 years' active service andfour years on the Reserve, and a cer-tificalte of nomination from the localEducational Authorities. This Edu-cational body willhold periodical ex-aminations at thechief centres, andsuccessful candidateswill be granted anomination certifi-cate for the R.A.F.The examination isnot a difficult one;it comprises a num-ber of elementaryquestions in mathe-matics and sciencewhich are calculatedto test the candi-date's general intel-ligence and estimatehis suitability forthe work to whichhe proposes to de-vote his future.

The successfulcandidate, after sat-isfying the MedicalOfficer with regardto his physical fit-ness will then pro-ceed to the Air Force Training Camp atHalton Park in the rank of Boy Mech-anic. Here the first six months of histraining will be. devoted to generalworkshop practice, physical training,sport, and general education. It willalso include the inculcation of that veryimportant and beneficial thing which isthe foster -mother of esprit de corps andhealthy comradeship in every service-the true spirit of discipline.

Photo by

On the completion of this prelim-inary stage the future airman willembark upon two and a half years ofspe&alised training at the WirelessTrainingSchool at Flowerdown Camp,Winchester. The Flowerdown Wire-less course is divided into five differentstages, each of which lasts a little overfive months, the balance of the time

being absorbed byliberal holidays dur-ing the summer andat Christmas. ' Atthe end of Stagea terminal examina-tion is held and asurvey of the resultsenables the ChiefInstructor to classi-fy all students as(a) satisfactory andready for furthertraining, (b) in needof a repetitioncourse, (c) unsuit-ed for further train-ing in this sphereof work.

In addition tothese terminal ex-aminations, whichare held at the closeof each stage, allBoy Mechanics areobliged to enter forthe City and GuildsElementary and Or-

dinary Examinations at the terminationof Stages I and II respectively, and, atthe end of the whole course-whenthe successful Boy Mechanic is imme-diately promoted to the distinctive rankof Leading Aircra ftsman-examina-tions are held for the City and GuildsAdvanced Certificate and also the Post-Master -General's certificate for Seaand Air.

This is certainly an excellent scheme

BassanbWing Commander J. B. Bowen, O.B.E.,

Commandant of Flowerdown WirelessTraining camp, Winihester.

623

THE WIRELESS WORLD

which cannot be praised too highly.Its inauguration marks the rapid de-struction of that almost insuperablebarrier which in the past too frequentlyseparated the " time served " soldier orsailor from his rightful place in the com-mercial world. Truly it was a valuablewar lesson which can claim respon-sibility for the fact that the time-.served airman of the future will stepback into civil life with certificatedqualifications at least as good as thosepossessed by the men amongst whomhe is going to compete in the nation'sindustry !

As it is outside the scope of thisarticle to enter into a detailed accountof the complete Wireless course, abrief consideration of the manner inwhich the subject matter of Stageis treated must suffice to indicate thevery high standard of efficiency whichcharacterizes the whole programme.Stage I is arranged in a very delightfuland ideal manner. The technicaltraining commences with a series ofintroductory lectures which are deliver-ed each day on such subjects as " ThePhysical Properties of Ether," " TheConstitution of Matter," " What areMolecules, Atoms and Electrons,"etc., etc. In conjunction with theselectures simple experiments are chosenand demonstrated with a view to em-phasizing the fundamental ideas setforth in the lectures. For example, inthe early part of the course, detailedexperiments are arranged whereby thestudents can with their own sensesobserve the various phenomena asso-ciated with positive and negative char-ges, static and current electricity,magnetic and electric fields, the rela-tionship between the pressure, current,and resistance in a simple electriccircuit, etc. All these fundamental,phenomena are demonstrated duringthe preliminary lectures and each pupil

FEBRUARY, 1.),o

is, afforded ample opportunity for re-peated investigation under his own man-agement. In this way, in the lightof his own individual discoveries,the student is encouraged to deducefrom personal observation, the most im-portant elementary principles -such asare embodied in Faraday's, Lenz's, andOhm's laws.

Great and justifiable attention isgiven to this aspect of the preliminarytraining. There is no attempt to cramor to insist on the memorisation of cum-bersome formula by rule of thumb.From the outset, no effort is sparedwhich is likely to assist the develop-ment of that attitude of interestedcuriosity than 'which no other attributeis so essential to the mental equip-ment of the student of science. As thecourse continues, the future wirelessoperator is introduced to those electricalproperties associated with the terms" Capacity," and " Inductance," andexhaustive experiments are conductedwith a view to establishing an accurateand indelible conception im-portant principles.

After this the student is familiarisedwith simple electrical measurementsand the next portion of Stage I dealswith the commoner types of secondarybatteries, their installation, and thenecessary precautions for their chargingand discharging, etc. Simple circuitsin connection with electric lighting arethen dealt with and the concludinglectures are devoted to the less complextypes of continuous current dynamosand motors.

The whole course' is hall -marked bya sound appreciation of the necessity ofcombining theory with practice. Eachday's programme includes the allocationof a suitable period for practical workin the Instrument Laboratory and theElectrical Workshops. In the Instru-ment Laboratory are carried out those.

624

TRAINING OF A R.A.F. WIRELESS OPERATOR.

lecture in progress.

elementary electrical .experiments towhich reference has already been made.In addition, the incipient wireless opera-tor is here instructed in the use ofvarious instruments employed in con-nection with electrolysis, general gal-vanometry, and calibration, specialattention being given to the measure-ment of resistances by the WheatstoneBridge, The Post Office Box, Meggers,etc. Here also dynamos and motors aresubjected to practical tests from theresults of which students are enabled toevolve and compare the " efficiencycurves " of individual machines.

In the Electrical Workshops is to befound a variety of lathes and tools, andwell -stocked benches such as . onlyexist elsewhere in the wildest dreamsof the ambitious wireless amateur.Here the young enthusiast is taught toattack a real practical job of work.Under the heading " Fitting and Turn-ing " the practical work of Stage 1

includes instruction' in the use ofordinary workshop tools, bench -work,forge -work, the use of treadle andpower lathes, drilling and boring,screw -cutting, etc., and due attentionis also given to the necessity for clear

and systematic diagrams and the cul-tivation of an ability to work directtherefrom.

In addition to the technical instruc-tion, an appropriate period is set asidein each day's programme for (a) Gen-eral Education, (b) Buzzer and VisualSignalling, and (c) Physical Trainingand Drill. The syllabus for generaleducation includes Practical Mathema-tics, English, Mechanical and PracticalDrawing, Elementary Physics andMechanics: In the Signal School,where Morse buzzer practice is in con-stant progress, the embryonic airmanis also trained as' an efficient exponentof the various methods of visual signal-ling which are employed by his brothers -in -arms, the soldier and sailor.

After an interval of five weeksStage II begins, and this is really anadvanced continuation and amplificationof Stage I. Stage II is also succeededby a test examination from which theindustrious and successful workeremerges with the key that opens thedoor to further scientific training.Another important process of selectionis applied at this period. All satisfac-tory students are now re-classified and

625

THE WIRELESS WORLD

each one is " labelled " as having shownan individual aptitude for such particularportions of his previous work as indi-cate his suitability for specializedtraining as (a) an Electrician, (b) aMechanic -Operator.

The remaining three stages are nowdevoted exclusively to eitherof these two branches ofstudy. Those who pursuethe career of an Electricianwill conclude their coursewith the City and GuildsAdvanced Examination, andMechanic -Operators willsit for the P.M.G.'s Certi-ficate for Sea and Air. Oneof the most important de-velopments in the econo-mics of wireless is ex-pressed in the term Mech-anic -Operator. During thewar we trained great numbers of mech-anics and great numbers of operators andthus practised a system of wastefulduplication that was only justified by theabnormal conditions and necessities ofthe moment. The straining demands ofthe war have now ceased however, and

Capt. H. Leedham,Chief of the Staff ofWireless Instructors

at Flowerdown Camp.

FEBRUARY, 1920

their withdrawal has rung up thecurtain on a new and more econo-mical organisation. The R.A.F.Mechanic -Operator of the future willbe, as his name suggests, an efficient" self-contained " unit. In the manystrange circumstances and climates

through which his adven-turous career must inevita-bly, lead him, the na-ture and quality of hisspecialized training will al-ways signalize him as animportant and independentlink in the chain of aero-nautical development.

The last three stages ofthe Mechanic -Operators'Corse are devoted to alltypes of Aerial Wireless,Telegraphy Instruments(spark and continuous

wave), Corps Squadron Work, Wire-less Telephony, and Wireless DirectionFinding.. They also include a lengthyprogramme of Aerodrome 'Practice -which assures that every qualifiedMechanic -Operator will have had con-siderable practic2l experience of working

ti+c

TRAINING OF A R.A.F.under difficult conditions during flight.Having successfully completed hiscourse the now full-fledged LeadingAircraftsman is available for dispersalto any of the various fields of wirelessactivity associated with the work ofthe Royal Air Force.

His first " job " may drop himneatly into the wireless cockpit of anaeroplane or seaplane, or the more lux-urious surroundings of the WirelessCabin on a giant airship. On the otherhand he may kick off with a warmerbillet in an Aerodrome W/T Station,a Direction Finding Station, or amotor launch used in co-operationwith seaplane work. Whatever bethe conditions under which he makeshis debui in the world of aeronauticalwireless he will find himself standingbeneath one of the many signposts thatpoint the way to an industrious andsuccessful career in the R.A.F.

It would not be fair to the originatorsand executors of this comprehensivesyllabus to omit reference to the im-portant and intelligent schemes whichare in operation in connection with theprovision of suitable opportunities forphysical and intellectual recreation

WIRELESS OPERATOR.

during leisure hours. Every form ofoutdoor sport is encouraged. Cricketand football, inter -School teams andleagues are in full swing at all times,and long lists of fixtures are arrangedwith outside schools and clubs andother branches of the service. A wellstocked gymnasium will provide themeans for passing many enjoyable andprofitable hours. For those who feelthemselves unduly burdened with a mul-titude of new and original ideas (andwho does not pass through this stageat some period or other ?) a debatingsociety affords ideal opportunity forconducting misguided fellow studentsinto the shining realms of truth. Anenterprising dramatic society is ever onthe look -out for fresh histrionic talent,and a well filled library strives to caterfor the most fastidious literary tastesand provides a haven of peaceful soli-tude for the thoughtful soul.

To crown all, if one is addicted tothe musical vice, no time need be lostin making arrangements to contributeone's just share to the unearthly dinwhich is responsible for the desolateand uninhabited aspect of the Camp onBand Practice evenings!

Operators in the Station at the Air Ministry.

C27

DOCTOR CORMLIS JOH4.7al'ES DE G7tOOT.

628

Personalities in the Wireless WorldOCTOR ENGINEER CORNELIS JOHANNESDE GROOT was born at den Helder on the 27th ofJanuary, 1883, graduated at the Technical HighSchool at Delft as Mechanical Engineer, and afterwardsobtained the diploma of Electrical Engineer atKarlsruhe.

After spending eighteen months in the service of the General ElectricCo. at Berlin he passed over to the Dutch East Indian Governmentand superintended the erection of various wireless telegraph stationsin the Indian Archipelago.

During his furlough in Europe in 1915-1916 he took his degreeas Doctor in Technical Science at the Delft University on the disserta-tion " Radio -Telegraphy in the Tropics," which work was afterwardspublished. The Doctorate was conferred upon him " cum laude "after his defence of the thesis :-" A Radio -Telegraphic Communicationbetween Holland and its Colonies without the use of relay stations ispolitically a necessity and technically possible."

Immediately upon his return to the Indies in 1916 he set to workto prove the practical feasibility of his scheme. Being promoted toChief of the Radio -Telegraphic Service in the Indies, he took up

with an installation partly ofhis own construction and by means of his receiver placed purposely onboard of H.M.S. de Zeven Provincien, he succeeded in keeping radio -telegraphically in touch with this war vessel all over the Pacific Oceanup to Panama, which was a record in wireless transmission from shoreto ship.

This special receiver was installed later on at the experimentalstation near Blaricum in Holland, and took the first wireless messageever received in Holland direct from Bandoeng. For this feat he waslionized and feted by the citizens of Bandoeng.

As soon as the transmitting station now being built in Holland iscompleted, a direct Radio -Telegraphic Service between Holland and itsColonies will be established.

One of Dr. de Groot's best known works is his paper entitled" The Nature and Elimination of Strays," which was read before theInstitute of Radio Engineers, New York.

629

JIIIIIIIIIIIIIIiIIIllllli111!111 11111111111111111111111 1111111111111111111111111 11 111111111E=

An Efficient Variable CondenserBY G. W. HALE.

NOW that the restrictionson Private Wireless aresomewhat relaxed andwireless enthusiasts allover the country are con-

templating the construction of theirapparatus, a description of an easilyconstructed variable condenser whichpossesses several advantages over theordinary semi -circular vane type willno doubt be appreciated.

The component parts of the con-denser are shown in the accompanyingsketches.

The rotor, Fig. i, consists of a discof ebonite or similar insulating ma-terial, the under surface of which shouldbe as flat as possible. The two semi-circular tin-or preferably copper-foil plates B and C are attached to theunder surface of the rotor by meansof shellac varnish, which should firstbe allowed to harden, the plates beingheld in position and then pressed witha hot flat -iron.' This method precludesthe possibility of moisture causing defec-tive insulation. Contact is made tothe right-hand plate C by means ofa round nut on the spindle as

t.

shown, while the left-hand plate Bis connected through the lug D to abrass or copper strip which is bentaround the circumference of the rotoras shown, and screwed at each endwith 6 BA countersunk brass screws.The Stop Pin E is a piece of brasswire screwed into the side of the rotor,and by working between the stops E,and E2 on the base (see Fig. 2), pre-vents the rotor from being turnedthrough more than 18e. The fixedconductors F and G (Fig. 2) areattached in a similar manner to thoseof the rotor and are connected to theirrespective terminals. The pillar atthe back of the base supports a brushof springy brass which should be setto bear evenly on the contact strip onthe rotor. The brush should be cutin two or three places so as to give thesmallest possible contact resistance.The wire J from the left-hand terminal,as shown by the dotted line, is sol-dered to a brass washer K, and thusmakes a connection to the rotor spindle.Between the upper and lower plates isplaced a disc of thin sheet -ebonite thors th of an inch in thickness. Photo-graphic celluloid film may also be used.The gelatine must be removed fromboth sides of the film, which may easilybe done by soaking it in warm water forabout five minutes, and scraping witha blunt knife. The rotor spindle isplaced through a recessed hole in thebase and secured underneath with acouple of nuts bearing on a springwasher and the washer K. Thespring washer should be compressedjust sufficiently to permit easy move-ment of the rotor. The adjusting

630

AN EFFICIENT VARIABLE CONDENSER.

Fig. 2.

knob and distance piece are drilled andtapped (2BA) and screwed on the spin-dle which should not project above theupper surface of the knob. The com-pleted instrument is depicted in Fig. 3.

For tuning a short wave receiversecondary the condenser described is

just right as its minimum capacity is

practically zero, a feature which is not

frequently met with in the ordinarymulti -vane type of condenser wherethe edge -to -edge capacity of the twosets of zinc plates is quite considerable,making it often necessary to disconnectit from the circuit altogether. Thisresults in a sudden reduction of wave-length, requiring a readjustment of in-ductance. When using a valve receiver

Fig. 3.

631

THE WIRELESS WORLD FEBRUARY, 1920

it is usually preferable to tune thecircuits with as little additional capacityas possible, relying on the inductance ofthe coils in conjunction with their owncapacities and that of the connectingleads to give the desired wavelength.As a guide to those readers who maywish to construct a condenser of this

I3/4

inches, Centre Hole, a inch.Spindle, 2BA Screwed Brass Wire

21 inches long.The base may be made from 4 inch

sheet ebonite and should be about4 inches long and 3+ inches wide. Ifdesired it could be made part of thepanel of a complete cabinet receiver,

11=1

.07 la'cur/caH-21

-7

Celuloid or Ebonite disc23/8"dia.Cenl-re hole 3/8-clia

2 B. A . Screw. 21/4"longFig. 4.

type the following dimensions may beof use (see Fig. 4).

Rotor (ebonite), diam. 2.* inches,thickness } inch.

Adjusting Knob (ebonite), diam. 4inches, thickness, z inch.

Distance Piece (ebonite), lengthinch diam. fi inch.

Celluloid or Ebonite Disc, diam. 4

2 -

C

according to the individual needs ofthe experimenter.

A Condenser made as described wasfound on test to have a maximumcapacity of 0.00017 mfd. using 44 thinch thick ebonite dielectric. The capa-city if celluloid film is used is somewhathigher as it is only about a fourth thethickness.

A FLEXIBLE SOCKET FOR WIRELESS RECEIVING VALVES.BY E. W. KrrcHIN, A.M.I.C.E.

THE usual rigid socket fora three -electrode valve hasthe disadvantage of beingunable to adapt itself toslight manufacturing vari-

ations in the " set " of the plugs whichform the electrode terminals. One ormore of the plugs may be slightly out

of the straight, involving the risk ofstrain if the valve is forced into a per-fectly rigid socket. The followingmethod of constructing sockets, re-cently devised and used with greatsuccess by the writer, produces a valvesocket with sufficient flexibility toenable a valve to be inserted easily and

632

FLEXIBLE SOCKET FOR WIRELESS RECEIVING VALVES.make good contact without risk ofstraining the plugs. It has the fur-ther advantages of cheapness and easeof construction, which will recommendit specially to the amateur.

Procure some brass or copper wireof No. i8 S.W.G., the correct gaugebeing important. Clean the wire well,and if of brass, soften it. Fix a " form-er " made of a short length of No. 10S.W.G. wire in .a vice, and wind thewire round it closely for nine or tenturns. Adjacent turns should touch,and the coil will be about half an inchin length. Care must be taken to windthe wire in such a direction that thecoil forms, as it were, a right-handedscrew thread. Tighten the coil onthe former by using two pairs of pliersin opposition, and make the end of thewire quite smooth. Leave on the otherend a few inches of straight wire, andfinally slide the coil bodily off the" former." One of these coils will herequired for every plug of the valve.

..1,1,1,1$1141 01111 IL

Having prepared a piece of sheetebonite of convenient size, and prefer-ably not less than / inch thick, pressthe plugs of a valve on a piece of paperwith sufficient force to leave a markfrom .each. Transfer this template tothe ebonite and mark through thepaper, with a sharp point, the positionsof the centres. Drill holes at thesepoints, and tap each with f inch Whit-worth thread.

Now carefully screw one of the wirecoils into each hole, starting from theunder side of the ebonite, until eachcoil projects about I inch above theebonite; the bottom end with the pieceof straight wire will then be aboutflush with the under side.

Fix four terminals in convenientpositions on the ebonite, and connecteach of the straight ends of wire toone of these, cutting off any surplus.

Attach four small feet to the underside of the ebonite base so that thewires and terminal bottoms will nottouch anything when in use, and theapparatus is complete.

If thicker ebonite than I inch is

used the coils should be proportionatelylonger, the idea being to have themflush with the under side and projecting

inch above.If carefully made, the coils will fit

tightly in the holes, but it is perhapsas well to spread them from the underside by forcing a tapering instrumentin, and giving it a few twists. Thiswill press the lower turns of the coilwell home into the screw thread cutin the ebonite.

The split plugs of the valve shouldbe carefully opened out somewhat ifnecessary.

The sockets may, if desired, be madestill more flexible by making the coilslonger and increasing the portionwhich projects above the ebonite base.This is, however, not recommended inview of the possibility of two adjacentcoils being accidentally caused to toucheach other.

633

111111.1111111.11111111111),11111,1 1111i 111111111111111111111111111111111111111111111I11111111111

Stray WavesF1711111111,11111111111111111111111111111111[11111111111111111111111111111.1111111111M Ilk 111111111111 FE.

THE AMATEUR POSITION.ON the surface the situation

has undergone no changesince we last went topress; the Government hasmade no further move and

there is no news of the promised Wire-less Telegraphy Bill. Yet the ama-teurs themselves are steadily alteringthe state of affairs, witness the persistentincrease in the membership of the exist-ing clubs, the rapid recrudescence ofclubs whose activities ceased when thewar broke out, and the numerous newclubs which spring into being everymonth.

We are glad to note that severalclubs have decided to affiliate with theWireless Society of London. Such acourse, we feel sure, will benefit thewhole amateur community withoutrobbing the individual clubs of theirfreedom to work along their own lines.

We are still under the impressionthat there are a number of clubs exist-ing with whoin we are not vet intouch. Will their Secretaries be goodenough to communicate with us, thusaiding us to complete our list. Weconstantly receive enquiries for detailsof the clubs nearest to certain towns.

* * *

POWER FROM THE SUN.Commenting on Sir Oliver Lodge's

recent Truman Wood lecture at theRoyal Society of Arts, Mr. A. A.Campbell Swinton, rn a letter toNature (Dec. 18, 1919), points outthat in referring to the probable highefficiency of vegetation as a utilizer ofsolar energy, the lecturer appeared to beunaware of the fact that Dr. HoraceBrown has shown that the actual

amount of energy stored is less than2 per cent of that reaching the vege-tation. This amount is, during day-light, more than 1,000 H.P. per acre.The main object of Mr. CampbellSwinton's letter is to.suggest that thereis probably a better way of utilizingsolar energy than by converting theradiation first into heat and he askswhether it is not worth while to con-sider the possibility of employing somemethod involving an action analo-gous to that of the thermionic valve, inorder to produce electric currents with-out an intermediate step.

*

RADIOGONIOMETER ANDTRIANGULAR DIRECTIVE

AERIAL PATENTS.We are requested by Mr. E. Bellini.

to give publicity to the following, inview of the item which we publishedunder this heading in our Dec. (1919)issue

" In the Numbers of October 24and 31, November 7, 14, 21, &c.,of The Electrician, page xxx ofthe announcements under the heading

Patent Rights for Sale, &c.,' Mr.Artom published under the above titlea short and confused note, from whichreaders could believe that the ItalianCourts had judged that the Radiogo-niometer, the Direction Finder and theTriangular Directive Aerial were in-vented by Mr. Artom.

" This affirmation is incorect. In1915 and 1917 in this same JournalMr. Artom had advanced the same pre-tension, which was the origin of apublic correspondence with Mr. Bellini.

" It is necessary to repeat here, in thename of truth and justice, that the

634

STRAY WAVES.

Italian Courts not only did not judgethis question, but, on the contrary, theyexplicitly declared that they had not todecide it. The translation of the partof the judgment containing the saidlimitation is as follows :--

It is not decided here whether theinventions, the subject of the ItalianPatents, slo. 88,765 and No. 88,766,were made by the scientists Brown andBlondel, or by Mr. Artom, or byMM. Bellini and Tosi. . "

WIRELESS POLICY INAMERICA.

A new policy for the control anddevelopment of wireless communica-tions in the United States was placedbefore Congress by Mr. SecretaryDaniels on October i5th. It pro-vides for maintenance of Naval andPrivate Stations, with the latter under

the control, of a National WirelessCommission. It deals with the licens-ing of Private Wireless Stations in thematter of assistance to Americans inestablishing wireless facilities withforeign countries. The NationalWireless Commission would attendBoard Meetings of Private Companies.Aliens or alien interest could not ob-tain licences from the Commission andall Officers and Directors of PrivateWireless Companies would have to beAmerican citizens and the majority ofthe stock of such companies wouldhave to be held by Americans. Pri-vate Wireless Companies would notbe permitted to affiliate with Submarine,Cable, or Land Telegraph or Tele-phony Systems without consent of theNational Commission, and would notbe permitted to operate in the Philip-pines or Panama Canal Zone.

THE NEW PATENTS ACT.For the benefit of those of our

readers who have to do with the patent-ing of inventions or who intend todevote themselves to investigationswhich may result in discoveries worthpatenting, we briefly describe hereunderthe alterations in the law which areembodied in the new Act. Firstly, theperiod between the filing of the pro-visional and the complete specificationshas been increased to nine months,-a very beneficial measure, as will befully appreciated by all who have takenout patents. Next, the Patent, underthe new Act, will be allowed to runfor sixteen years, an increase of twoyears, the advantages of which areobvious.

A number of rules are laid down toprovide against abuses of the PatentLaw by foreign inventors, who wereformerly able to dodge the law to the

disadvantage of British patentees. Un-der special clauses the British inventoris protected much more than formerly.All patents must be worked withinfour years.

In respect to claims an amendmentis enacted whereby the inventor whofinds it necessary to prosecute forinfringement, need only prove thevalidity of his principal claims. Underthe old law, if he failed to support anunimportant subsidiary claim he losthis action and the infringer reaped thebenefit of his malpractice until theinventor amended his specification.

The extensions of the terms ofpatents has been altered from seven andfourteen years to five and ten yearsrespectively, and the Act has beenmade retrospective, thus prolonging fortwo more years patents which otherwisewould expire this year.

635

- Digest of Wireless LiteratureTHE SELF -OSCILLATIONS OF

A THERMIONIC VALVE.BY R. WHIDDINGTON, M.A., D.Sc.

Cambridge University Reporter, May27th, 1919, also Radio Review,

November, 1919.IT has been found possible to pro-

duce oscillations of almost anyfrequency by means of a three -electrode valve without employingthe usual capacity -inductance cir-

cuits. A soft valve is used which con-tains sufficient quantities of gas orvapour to permit of collisional ionisa-tion taking place. Fig. 1 shows thecircuit normally employed for the pro-duction of these oscillations. It willbe seen that there are here no capacity -inductance circuits whatever as theresistance R is non-inductve, consistingnormally of a soft lead pencil splitlengthways and fitted with a smallmetal sliding contact. With batteriesof suitable magnitude strong oscillationsmay be set up in this circuit the fre-quency of which is determined almostentirely by the value of the grid poten-tial and the geometry of the valveelectrodes. These oscillations can bedetected, and their wavelength mea-sured by means of an ordinary hetero-dyne wavemeter placed near the circuit.

B,

To account for these oscillationswhich, broadly speaking, are to beregarded as being due to periodicsurges of mercury .ions closing in onthe filament, one must assume thatalthough the filament as a whole is emit-ting electrons continuously according toRichardson's law, yet there are oftenisolated spots which emit with excep-tional power. If this is granted it alsoseems reasonable to assume that thebombardment of the filament by rapidlyinoving positive ions in the neighbour-hood of such an emitting spot wouldgreatly increase the local emission.

A burst of electrons starting fromsuch a spot on the filament would travelfrom filament to grid under the influ-ence of the small grid potential nor-mally used. On passing through thegrid interstices the electrons travel intothe strong electric field of the anodeand attain sufficient velocity to producecollisional ionisation among the residualmercury atoms in the tube. The posi-tive mercury ions so formed now travelback to the filament and bombard theoriginal emitting spot, causing anotherburst of electrons to travel towards thegrid and cause the whole process to berepeated in a regular' manner. Onaccount of the repetition of this cycleof operations the anode current is of apulsating nature and thus may be re-garded as possessing both a steady andan oscillatory component. On thistheory it may be shown that the fre-quencv n of the oscillation set up isgiven by the formula

n2 = 2 . e . V (1)

where --- is the charge to mass ratio of

the positive ion concerned, d is theradial distance of filament to grid, and

636

DIGEST OF WIRELESS LITERATURE.

V is the positive grid voltage. Thismethod of producing oscillations sug-gests a wireless method of determining

the value of - as the other quantitiesni

of equation (1) can be measured. Italso suggests the possibility of producingextremely short wireless waves by amethod entirely different from the onesnormally employed.MESURE EN VALEUR ABSO-LUE DES PERIODES DES OSCIL-LATIONS ELECTRIQUES DE

HAUTE FREQUENCE.BY MM. HENRI ABRAHAM AND

EUGENE BLOCH.Annales de Physiques, Oct. 1919.The exact determination of the

wavelength of electrical oscillationsis the basis of all high frequency mea-surement. Its importance is particu-larly evident in the calibration of wave -meters for practical work in radiotele-graphic transmission. However, now-adays things are quite different. Thedevelopment of Wireless Telegraphy inall directions has caused the multiplica-tion of sending stations. Also the useof continuous waves, introducing thepossibility of exceedingly fine tuning,requires that our wavemeters should bemuch more accurate than they wereformerly.

The new method proposed for thecalibration of wavemeters consists indetermining not the wavelength of theoscillation but the period. This periodis determined by making it identical.

MULTIVIBRATEUR

with that of a harmonic of a low fre-quency valve oscillator, the frequencyof which can be made identical withthat of a standard tuning fork. Forexample, if a tuning fork of a frequencyof 1000 is used a wavemeter can betested at a frequency of 150,000(X = 2000 metres approximately) pro-vided the valve oscillator emits har-monics up to the 150th. An ordinaryheterodyne wavemeter emits harmonicssay up to the 12th but by using aspecial circuit (known as a " multi-vibrateur ") it has been found possibleto obtain harmonics with a frequency300 times that of the fundamental.

The full set of operations may thusbe briefly summarized as follows :-(a) The frequency of the standard

tuning fork is determined exactlyby comparison with a standardclock.

(b) The fundamental frequency of themulti-vibrateur is made equal tothat of the standard tuning fork.

The wavemeter is now calibratedby comparison with a harmonic ofknown order. Electrical reson-ance is utilised for this adjustment.The wavemeter circuit is coupledvery loosely both with the multi-vibrateur circuit and also with adetector -amplifier. A heterodynecircuit is loosely coupled to thelatter to enable the adjustment tobe made by means of an audiblebeat note. The arrangement usedis shown in Fig. 2.

AMPLIFIER

(c)

Fig. 2.

637

HETRODYNE

vah

-J111111111111111111111111111111111111111111-11111111111-11111111111111'111111111111111111111111111111111

Notes on the Physics ofthe Thermionic Valve

By T. G. PETERSEN.

(Continued from January Number.)

ALTERATION OF ANODE DIAMETER, ORDISTANCE FROM FILAMENT.

iT is not proposed to deal at anylength with the alteration of anodediameter, since the idea of the strayfield and the counter field (orassisting field, as the case may be)will now have been thoroughly

grasped, but a passing reference shouldbe made to Fig. 11. It will therein benoted that when the -plate is in positionP1, Es will have a certain value, butwhen at P2 this value becomes less,until in position P,, it becomes zero.

E.

F

E.

P,

Fig. ii.

Hence, the general statement may bemade, that the combined effect of thegrid and a negative potential impressedon it tending to diminish the valvecurrent, is increased when the plate ismoved away from the grid.EFFECT OF SPACE CHARGE ON SLOPE

BETWEEN G AND F.It will have been noticed that the

existence of a spacecharge betweengrid and filament has, up to the present,

been ignored. When it is rememberedthat this is. a negative charge situatedbetween grid and filament it will bereadily understood that it will havesome effect upon the slope along thisportion of the field Es. Now the spacecharge only exists when electrons areemitted from the filament at a fasterrate than they can be carried away byattraction of the .field Es. Thus anyexcess of electrons will set up anelectric field counter to Es. If thenwe regard the conditions in this manner,it is seen that the result upon the slopeof Es will be analogous to that obtainedby decreasing the mesh of the grid orincreasing a negative potential on thegrid, as already outlined.

A conception of the effect upon theslope between G and F is shewn inFig. 12, in which the plate has beenleft out. The height HG representsthe value yEs, but this is reduced, byreason of the counter field of FJ toKG, which is equivalent to yEr, - Ec.SC,, SC,, and SC, represent the loca-

638

Fig. 22.

PHYSICS OF THE THERMIONIC VALVE.

tion of the space charge and FL, FM,and EN are proportional to the in-tensity at the respective points. De-ducting FN brings the slope down to 0,similarly deducting FM and FL lowersthe corresponding points of the slopeto R and Q respectively. The slopetherefore becomes curved similar to theline F, Q, R, 0, K, which shows clearlyhow the velocity of electrons leavingthe filament may be seriously decreasedwhen the space charge is present.

OPERATING CONSTANTS.

Owing to the vast amount of researchwork which has been carried out bymany prominent wireless and otherexperts, a number of the constants ofthe three -electrode valve, which werenot long ago more or less unknownquantities, may now be deduced fromits structural dimensions and theapplied potentials. Therefore in additionto the store of information regardingvalves thus provided, their design isgreatly facilitated. Amongst the con-stants which are most important arethose contained in the appended list.There are others, but they are hardlywithin the scope of these elementarynotes. We will therefore limit ourconsiderations to the four factorsenumerated :

Factor

Plate CurrentVoltage Amplification FactorMaximum Voltage Amplifi-

cation FactorPlate Resistance

Sign

I

PLATE CURRENT.Various formulae have been given for

the calculation of the plate current 1 ;for instance, Langmuir gave

I = a (E KEg) 3 (1)

in which E is the plate voltage, Eg thegrid voltage, K the maximum voltageamplification factor, and a is a factordependent upon the valve dimensions.

Van der bijl has shown that I can1 e calculated from the equation :

I = a (yEi, Ec e)2 (2)

in which a and are constantsdepending on the dimensions of thevalve (see preceding remarks). EB andE, correspond to E and Eg of Lang-muir's formula (1) and y (gamma) isthe reciprocal of the maximum voltageamplification factor.

But for practical purposes the platecurrent can be calculated from Lang-muir's original emission currentequation, in a revised form, whichconsiders the action of the grid by theinclusion of the function p.o, thus :

6 1 (E .... (3)I =14.65 x 10 - -+ )tY

That this satisfies the case for practicalpurposes will be seen by reference toFig. 13, which shows the plate current-grid volts characteristic of a typicalV24 valve, for seven different platevoltages.

Taking the values as follows : / -=2 cms., v =0.686 cms., E = 35 volts,Eg = 4 volts, and tzo = 7, we obtainthe following result :

I= 14.65 x 10-6 2 35 3x - -0.686(7+)=1.15 milliamperes.

It should be noted, in passing, that

639

3.6 -

2-4 -

4 6GRID VOLTS

/-'1,` 1 3 .

41]

350

285

0222

150

8-0

0

THE WIRELESS WORLDin plotting the values in Fig. 13 a seriesresistance was used in the negative endof the filament, across which there wasa voltage drop of approximately 1.5volts, so that Eg corresponds to theposition 5.5 volts (positive), along thex axis.

The method (3) replaces the constant

a in (1) and (2) by 14.65 x 10 and,

since the computation of these con-stants is rather a complicated process,offers a ready means of ascertainingmathematically the approximate valueof the plate current obtainable, givencertain constants.

It is interesting to note that the valueof plate current obtainable in moderntransmitting valves exceeds 350 milli-amperes, even when the grid is main-tained at a high negative potential. InFig. 14 are depicted three curves show-ing the plate current values, at 4,000,6,000, and 8,000 volts, of a mediumpower transmitting valve.

252-

n

0.1.1

J

XI 40z

a

28

120 80 40 6 40 80GRID VOLTS.

1-1

FEBRUARY, 1920

VOLTAGE AMPLIFICATION FACTOR.

In the case of a valve to be used asan amplifier, one of the chief of itsconstants is that which denotes itsvalue of magnification. Such factormay be termed its voltage amplificationfactor, and is expressed as a ratio ofchange in voltage on the plate, for aconstant plate current.

For instance, let us suppose that withthe grid of a valve 5 volts positive, andits plate 50 volts positive, a current of2 milliamperes flows in the platecircuit. Let the plate voltage belowered to 41 volts (i.e., a decrease of9 volts) ; then if by increasing the gridvoltage to 6.5 volts (i.e., an increase of1.5 volts) the plate current remains thesame, the voltage amplification factor

1 .5at this point is - 6.

9

It will thus be seen thatµ can befound practically by plotting thecharacteristic plate current-grid voltscurves for various plate voltages, and itis now proposed to show the method ofoperation. It is not possible to readthe value of /A. directly from the curves,but it is necessary to construct twocurves from these, plotting plate currentagainst plate volts. Call the first ofthese derived curves A, and let it berelative to a constant grid potential of5 volts positive ; then the following setof. values will be obtained from thecurves of Fig. 13.

Anode volts. Plate current.8 0.25

15 0.512.2 1.7528.5 3.535 6.541.5 9.5

and plotting these we obtain curve A.Similarly, plot curs e B correspondingto a positive grid voltage of 6. volts.Both of these curves are shown inFig. 15.

We have thus made a change of onevolt on the grid (i.e., from 5 to 6 voltspositive) and can see at a glance the

20 value of the decrease in plate voltsnecessary to obtain the same platecurrent at the higher grid voltage.

640

PHYSICS OF THE THERMIONIC VALVE

It will be noticed that the value µvaries when the operating position onthe slope of the curve is altered ; in awell -designed valve, however, themaximum value µ0 is where the grid isat zero potential with reference to thefilament.

The µ0 of several modern valves isgiven in the appended list.

Receiving Transmitting

6 MARCONIV24

50 MARCONI

Q

200MARCON I

MT 1

PLATE RESISTANCE.

For low -frequency currents the im-pedance of the plate circuit-internalto the valve-is in the nature of a pureresistance, and it is only when high -frequency currents are present that theinter -electrode capacity of the valvetends to lower this value. Since weare here not concerned with high -frequency currents, the consideration ofR. will be limited to that of true ohmicresistance. That this resistance of theplate (sometimes called the internalimpedance) is a variable quantity will

2.4

1.2

0 10

be seen by reference to Fig. 15. Forinstance, when working with 26 voltson the plate, and with the grid between5 volts and 6 volts positive, the resis-tance Ro is

EP 5.8757 8

- 1 00 w.0.00033 '

but with 37.5 volts on the plate Ro

becomes 6.375 - 16170 w. Hence,0.00039

as the plate voltage is increased, thevalue of Ro decreases for a given gridvoltage.

The necessity of first evaluating µbefore Ro can be determined, makesthe process a rather lengthy and com-plicated one, since this involves theplotting of two sets of curves similar tothose of Figs. 13 and 14. In order,therefore, to obviate this tedious opera-tion, Stewart Ballantyne (Proc. I.R.E.,April, 1919) has evolved a dynamicmethod for finding Ro directly, basedon the bridge principle.

The circuital arrangement is depictedin Fig. 16.

This method has the advantage ofsimplicity, and a series of curves mayquickly and accurately be obtained byits aid. RiR2 is a slide wire, and R isa known non -inductive resistance ofapproximately the same value as the

20Fig. 15.

641

3C 40

4

Fig. i6.

plate resistance. The method of operation is as follows : An intermittent d.c'or an a.c. is sent through R,R2, andthe pointer is then moved along it untilthe current through the balance leadfalls ' to zero, namely when signalsvanish. Ro is then obtained by multi-

plying R by the ratio -,. In the com-RR2

pilation of the curves in the concludingfigure (17), the source of the currentpulses was a high -note shunted buzzer ;R, R2 consisted of a yard length ofnumber 36 Eureka wire and R of aRemo:, resistance rod of 19,7000)resistance.

The curve which is of most interestis that corresponding to 50 volts on theplate, since it is almost symmetricallyplaced with reference to the detectingpoint. It may appear a little curiousthat R0 should go up after a certainpositive value of grid volts is increased,but this is due to the fact that gridcurrent is flowing, to the right ofminimum resistance.

This value of anode volts change,divided by the grid volts change (inthis case, one volt), denotes the valueof /.4, at that particular value of platevoltage. In the two cases shown, i.e.,c - d, e-f, the values are 6.3 and 5.9respectively.

From the case above mentione I itwill be seen that letting

V, = higher plate voltage.V, = lower plate voltage.Vg = the change in grid volts

for constant plate current, then

V, - V.,µ= Vg

and substituting in the case e -f(Fig. 15),

(4)

R,


V1 - V, 28.5 - 22.6= 5-9= Vg. - 1

The method outlined above entailsthe construction of curves, which occupya good deal of time in operation andplotting; it may be, therefore, an in -

R convenient process if an approximatevalue is all that is desired, and aquicker method may be more suitable.Such a method should already havebecome obvious to the reader fromwhat has been said. Having ascer-tained experimentally the point atwhich grid current starts, note theplate voltage and current. Now de-crease the plate volts and increase thegrid volts till the plate current hasreached its former value. It will beseen that in this operation one is, inreality, selecting the desired pointson the characteristic curves, and thatvalues may be substituted in equation(4) and p. be obtained in this manner.

CALCULATION OF p,o FROM VALVEDIMENSIONS.

The factor p, of a valve with cylin-drical electrodes may be calculatedwith accuracy by the formula below,due to Sir J. J. Thomson, to whomthanks are due for permission to publish.

TO PHONES

WNW

P,0 =d' N log

log CreigiN)(5)

whered' = diameter of grid in centimetres.du = diameter of anode in centimetres.N = number of turns per cm. length

of grid.dg = diameter of grid wire in cms.

It will be noted that this formuladoes not include any eh ctrical units, hutshows the factor if.to directly from thedimensions and disposition of theelectrodes. It will pei haps be of interestto see how the calculation compareswith the actual case of the receivingvalve mentioned above. The valuesare :

di = 0.32 cms.dg = 0.023 cms.

642

65000 -

0000 -

55000

50000-

45000-

40000-

35000-

30000-

25000-

20000-

15000-

10000-

5000-

PHYSICS OF THE THERMIONIC VALVE.

115 VOLTS

86 VOLTS .

50 V OLTS

GRID VOLTS WITH REFERENCE TO NEGATIVE END OF FILAMENT.

I 0 I 2 3 4 a a 7 8 9 i0 if 1.2 t'a

Fig. x7.

643


du = 0.685N = 6

and substituting in formula (5) andworking the numerator first, for thesake of clearness, we obtain

3.1416 x 0.32 x 6 x log (.685) -1.99.32

and for denominator we have1 - 0.3450.023 x 61°g (3.1416 x

1.99/4° - 0.345 - 5-8 nearly.

It will be noticed that the anodediameter, and the thickness of the gridwire, are considered in the equation (5),as indeed they should be ; but providedthe valve is designed correctly these

two values may be disregarded, andthe expression

pc, = 2 it r N (6)

will be found to be sufficiently true forpractical purposes. The symbols r andN refer to the radius of the grid, andthe number of turns on the grid respec-tively. When the grid is composed ofa mesh, the value of p, will be roughly4 7 r N, in which case N represents thenumber of meshes per centimetre.

Other direct methods of obtainingthe voltage amplification factor havebeen devised, such as Miller's (Proc.I.R.E., vol. vi., 1918) and Allen's(WIRELESS WORLD, November, 1918),but reference should be made to thedescriptions of these methods as givenby the originators. -(To be continued.)

The Library Table5111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111i111111111F,

THE WIRELESS AMATEUR'SDIARY AND NOTEBOOK.

The Wireless Press, Ltd. 4/6 net.T HIS is an attractive look-

ing production consisting oftwo separately bound partsinserted in a stout pig -skinfolder which has special

accomodation for stamps, visiting -cards, treasury notes, and private papers.The first part should go straight to theamateur's heart for it contains just thekind of information he is always askingfor, such as a list of the world's chiefhigh -power stations with details of thesystems and wavelengths used, muchuseful data which has been compiledwith an eye to what the amateur reallyneeds, and a series of well -drawntypical valve circuits. Space is pro-vided for a directory of amateur wire-less stations and for " Receiver Notes "wherein the amateur can jot down thevarious adjustments of his instruments

for certain wavelengths. There isalso a 1920 Calendar and a large quan-tity of directly useful miscellaneousdata, followed by a diary and notebook.The second part consists entirely of theever -useful squared paper. The casemeasures 3" x sr and tits into the aver-age top vest pocket quite comfortably.

THE WIRELESS OPERATOR'SDIARY AND NOTEBOOK.

The Wireless Press, Ltd. 4/6 net.With the exception of some items

which have been specially prepared forthe benefit of professional wirelessoperators, this notebook is identicalwith the one described above. It con-tains a list of the principal stations onthe ocean routes, a table for calcula-ting tolls on messages, notes on freaksand long-distance communications, andon the best adjustments of the receiverfor various wavelengths. It also in-cludes the valve circuit diagrams.

644

1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111_

Notes of the MonthFdIm11111111111111111111m11111iiiiiiIiiiiii11111111111111ffiliiiiii111111111111111rnimmff

THE STEADY MARCH OFWIRELESS.

The Amalgamated Wireless (Aus-tralasia) Ltd. have received an orderfor a complete wireless installation fordirect communication between' Nukua-lofa and Suva.

3

The Council of Ministers, Colombia,has approved the terms of a contractfor installing a wireless station inPuerto Velillo or some other point onthe coast. The plant is to be powerfulenough to maintain day and night com-munication with the station which theMarconi Company is to erect at Bogota.

A station is also to be constructed inone of the islands of the St. Andresand Providencia Archipelago.

A wireless station has been installedat Cobija, Bolivia, for communicationwith other parts of the Republic andwith Brazil.

The Venezuelan government hasinvited tenders for the construction ofa wireless station to be situated in theneighbourhood of Caracas, which mustbe able to communicate with the U.S.A.and Europe. The specification pro-vides for both C.W. and spark systems.

CANADA-BERMUDA WIRE-LESS SERVICE.

The Department of the CanadianNaval Service at Ottawa announces theinauguration of a commercial wirelessservice between Canada and Bermuda.The, service will be established by theCanadian wireless station at BarringtonPassage, Nova Scotia, and the BritishGovernment station at Bermuda.

The Stavanger wireless station inNorway has now been opened. Com-munication will he held with the Anna-polis station at Washington and theTuckerton station near Philadelphia.

sRestrictions in force during the war

with regard to the use of wireless bymerchant vessels in Argentine watershave now been removed.

NEW CALL SIGNALS.The following alterations and

additions are notified by the BerneBureau:-

ETAFFCFFHFFMFFNFFUFFXFUCFUDFUEFUIFUKFUNFUQFURFUX

Algiers.Bonifacio.Le Havre.Marseilles.Nice.Ushant.Bordeaux.Cherbourg-Rouges-Terres.Dunkirk-Castelnau.Mengam.Ajaccio-Aspretto.Aran AM el Turck.Lorient-Pen-Mane.Porquerolles.Rochefort-sur-Mer.Toulon --Croix des Signaux.

PUBLICATION OF TECHNICALW/T ARTICLES.

The War Office states that it hasbeen decided to allow experts (eithermilitary or civil) employed on wirelessduties in the Army, to write scientificpapers for publication in this country.The form of publication may be eitherby journal or by lecture, provided thatno detailed reference is made to ServiceSets and that the paper is forwardedthrough .the usual channels to the WarOffice, whence it will be passed forcensoring to the Wireless. Telegraphy

645

THE WIRELESS WORLD

Board. Papers for censorship shouldbe submitted at least a month beforeit is desired to publish them.

NEW APPOINTMENT.Acting Captain J. A. Slee, C.B.E.,

R.N., has been appointed TechnicalSuperintendent and Adviser on the staffof the Marconi International MarineCommunication Co., Ltd.

* *

I.E.E. AWARD.The Council of the I.E.E. has

awarded the David Hughes Scholar-ship of £So to Mr. Bernard Cronin,of the University College of SouthWales and Monmouthshire.

THE HIGH -FREQUENCY RESIS-TANCE OF WIRES AND COILS.

An interesting paper on the abovesubject was read by Professor G. W. 0.Howe, D.Sc., at the ordinary generalmeeting of the Institution of ElectricalEngineers, held at the Institution ofCivil Engineers on Wed., Dec. 17thlast, followed by a discussion in whichProfessor C. L. Fortescue, Dr. W. H.Eccles, Messrs. P. R. Coursey, H. W.Taylor, F. Murphy, and R. C. Clinkertook part.

SUCCESSOR TO SIR OLIVERLODGE.

Mr. Chas. G. Robertson, C.V.O.,has been appointed Principal of Birm-ingham University. He has beenTutor in Modern History at MagdalenCollege, Oxford, since 1905.

* * *

AWARD FOR PHYSICS.It has been decided to award the

Kastner-Boursault prize for Physicsto M. Marius Latour. This gentle-man, .who is a certificated engineer ofl'Ecole superieure d'Electricite, is, well-known in wireless circles for his work

FEBRUARY, 1920

on H.F. alternators in connection withwireless telegraphy, and on the ther-mionic valve.

WIRELESS TO ROME.A special wireless service between

England and Italy for the use of thenewspaper Press was opened on 6thJanuary last by the Marconi Company.This service, authorised by the ItalianGovernment and the British Post Office,was instituted particularly to assist theItalian Press in obtaining prompt reportsof the Italian Prime Minister's visit toLondon. The Marconi high -powerstation at Carnarvon is being used forthe purpose and three hours daily havebeen allotted for this particular traffic.

AWARD TO DR. WIEN.The T echnische Hochschule of

Danzig has conferred upon PrivyCouncillor Dr. M. Wien, Professor inordinary of Physics at the Universityof Jena, the rank of " Honorary DoctorEngineer " in recognition of hisachievements in the domain of oscilla-tion phenomena and especially for hisdiscoveries relating to the effect of thequenched spark.

*

THE PHYSICAL SOCIETY OFLONDON.

At the tenth annual Exhibition heldby the Physical Society of London andthe Optical Society at the ImperialCollege of Science, South Kensington,on January 7th and 8th last, therewas a fine display of Wireless Appara-tus. The Exhibits included : Therm -ionic Valves, shown by the Marconi-Osram Valve Co., demonstrating theevolution of the valve.-DirectionFinders (Marine Pattern), MeasuringInstruments, Various types of Valves,etc., shown by Marconi's WirelessTelegraph Co., Ltd.-Various types ofCondensers, shown by the Dubilier Co.,

64t

NOTES OF THE MONTH.Ltd.-Induction Coils and Transform-ers, shown by the High Tension. Co.-Three -Valve Amplifying Receiverand a series of Condensers, shown byMessrs. H. W. Sullivan.-A new Wire-less Condenser of extra fine adjustment,named the " Phantom," shown byMessrs. Isenthal Sc Co., Ltd.-A Seriesof Thermionic Valves, shown by theEdisqn Swan Electric Co., Ltd.

CATALOGUE OF WIRELESSAPPARATUS.

It may interest amateurs to know thatMessrs. H. W. Sullivan's new catalogueis now in the press and will be readyfor issue during the early part ofFebruary.

WIRELESS CLUB NOTES.THE WIRELESS SOCIETY OF LONDON

The Wireless Society of Londonwill hold its next meeting at the Insti-tution of Civil Engineers, Gt. GeorgeStreet, Westminster, on January 29th,at 6 p.m., when Mr. R. C. Clinkerwill deliver a lecture on " A PortableValve Set and some Properties of C.W.Circuits," which will be illustrated byexperiments and lantern slides.

The Presidential Address will takeplace towards the end of February atthe Institution of Civil Engineers.Notice of the exact date will appearin the next issue. Those who wereprivileged to attend the last PresidentialAddress given by Mr. A. A. Campbell -Swinton, F.R.S., in 1914, will lookforward with pleasure to some novelexperiments, with which the President'saddress will no doubt he illustrated.

* *

THE BURTON -ON -TRENT WIRELESSCLUB.

(Affiliated with the Wireless Society ofof London.)

On December 17th, 1919, a well -attended meeting was held. Mr. A.

Chapman, presiding, stated that a num-ber of books were now available andcould be borrowed by members. Healso stated that the wireless room wasnot up to then equipped with a valve, butthat excellent reception was, however,being obtained. Four new members wereelected. The Secretary announcedthe affiliation of the Club with theWireless Society of London.

Mr. A. J. Selby then gave a demon-stration of electricity and magnetismwith home-made instruments, and Mr.R. Chapman (late R.A.F.), repliedto several questions on the higherprinciples of wireless.

Hon. Sec., Mr. R. Rose, 214,Belvedere Rd., Burton -on -Trent.

THE NORTH MIDDLESEX WIRELESSCLUB.

(Affiliated with the Wireless Societyof London.)

A meeting of this Club was held onDecember 31st, 1919, at ShaftesburyHall, Bowes Park, the President, Mr.A. J. Arthur, being in the Chair.Addressing the meeting, Mr. Arthurannounced that it was hoped that theaerial pole would be delivered in thecourse of a few days, and asked thatsome members would form a workingCommittee to look after. the erectionof the pole and install the instruments.Several names were at once handed in.He then called on Mr. Geo. W. Evansto give his address on the constructionof Variable Condensers.

Mr. Evans then gave a most instruc-tive talk, and he having brought a num-ber of variable condensers of differenttypes, members were able to gain a lotof useful information.

The chief difficulties likely to be metwith were explained, and the salientpoints of each type of instrument werepointed out. A short discussion then

647


followed, at the close of which Mr.Savage moved a vote of thanks to Mr.Evans, and at the same time drew theattention of those present to the neces-sity of more lectures of that nature, andasked members to come forward withsuggestions.

For particulars of the Club apply tothe Hon. Secretary, Mr. E. M. Savage,Nithsdale, Eversley Park Road, N. 21.

THE DERBY WIRELESS CLUB.(Affiliated with the Wireless Society

of London.)The Annual General Meeting was

held on Jan. 2nd, when the Secretary,speaking on behalf of the Chairman,Mr. S. G. Taylor, who was unable tobe present, dealt with the amateursituation and recent developments ofwireless. Reviewing the present posi-

tion of the Club, he stated that themembership is now 58 as comparedwith the pre-war total of 120; this heattributed to the fact that many of theCorresponding Members had nowjoined clubs in their home towns.

Regret was expressed that Sir HenryNorman, M.P., was unable to continueas President, and it' was announced thatMr. F. W. Shurlock, B.A., B.Sc., hasconsented to be President for the year.Mr. S. G. Taylor was re-elected Chair-man, Capt. W. Bemrose, O.B.E., Hon.Sec. and Treasurer, and Mr. J. Lowe,Librarian. The Committee were alsoelected, a draft of new Club Rules wassubmitted and approved, and it wasresolved to affiliate the Club with theWireless Society of London.

The meeting was followed by anexhibition of apparatus. Mr. S. G

Fig. 1, Portable Receivers exhibited by Mr. A. T. Lee at the Derby Wireless Club.

648

NOTES OF THE, MONTH.

Taylor showed, amongst other things, acompact single -valve receiver, the wholeof which was contained in a cigar -boxmeasuring about 7"x 4" x 2 Mr.A. T. Lee showed two portablereceivers, specially built by himself foruse on' aircraft (Fig. I). Capt. Bern -rose exhibited a five -valve amplifier ofhis own construction (Fig. 2), and Mr.J. Huson showed some German vari-

Fig. 2. Amplifier Exhibited by Capt. Bemroseat the Derby Wireless Club.

able condensers and other parts ofradio apparatus. Messrs. Newton Bros.kindly lent three W/T. generators asused on aircraft.

The Secretary (Little -over -Hill, Der-by) will be pleased to hear from old orintending new members.

THE MANCHESTER WIRELESS CLUB.

(Affiliated with the Wireless Societyof London.)

The first General Meeting tookplace on December 17th, 1919, at theClub Rooms, 335, Oxford Street, Man-chester. A large and representativegathering of members was present,most of whom had seen service of

'an important nature as wireless opera-tors in H.M. Forces.

The Committee has lost no time

in getting to work, and already a splen-did series of lectures has been arrangedfor the session.

Through the kindness of the Princi-pal of the Universal School of Tele-graphy, the members have been allowedthe use of practice rooms and instru-ments, and also the use of a workshop,which is a great boon to the amateur.

The Club is now open to receiveapplications for membership, and everyhelp is given to the new bona fidewireless experimenter in designing andconstructing his instruments.

Morse Code practice takes placeevery Wednesday at 7 p.m.

Full particulars may be obtainedfrom the Hon. Sec., 16, HawthorneAvenue, Monton, Eccles, Lancs.

THE THREE TOWNS WIRELESS CLUB(PLYMOUTH).

December 3rd, I919-The Chair wastaken by Mr. J. Jerritt, and a lectureon " Condensers and their Uses " wasdelivered by Mr. Voss (late R.F.C.),at the conclusion of which the Hon.Sec. (Mr. W. Rose), drew a number ofdiagrams illustrating how an ordinaryvane type condenser may be speciallyadapted for valve work.December loth, 1919-Mr. J. Jerrittin the Chair. The evening was de-voted to Morse practice and a discussionon a variometer brought by the Hon.Sec. and kindly lent by Messrs. An-tenna: Instruments, 50, The Promenade,Palmer's Green. Although guaranteedto be efficient only up to 8,000 metres,this instrument worked well up toIo,000 metres.

The club is still waiting for itsP.M.G. " permission," as also are someof the members.

The Hon. Sec., Mr. W. Rose,7, Brandreth Rd., Compton, Plymouth,will be pleased to see visitors or intend-ing members.

649

THE WIRELESS WORLD

THE WIRELESS AND EXPERIMENTALASSOCIATION.

A lecture on internal combustionengines was delivered on Jan. 7th byMr. J. F. Sutton, illustrated withdiagrams' and dealing chiefly with thesmaller types. Reports of the otherJanuary meetings will be given in ournext issue, as they will not occur untilafter this number has gone to press.

Intending members please address theSecretary, Mr. F. H. Gribble, 48,Surrey Square, S.E. 17.

THE SHEFFIELD AND DISTRICTWIRELESS SOCIETY.

No reports of recent meetings havecome to hand (will the Hon. Sec. kindlynote ?) but we must mention that wehave received a copy of the PresidentialAddress which was delivered on Oct.2nd, 1919, by Mr. H. E. Yerbury,M.I.C.E., M.I.E.E., M.I.Mech. E., atSheffield University. It is a mostinteresting pronouncement, upon whichwe congratulate the Society, and we ven-ture to suggest that some of the otherSocieties would be repaid by devotingan evening to a discussion of the paper.We shall be delighted to lend our copyif others are unobtainable.

Hon. Sec., L. H. Crowther, 156,Meadow Head, Norton Woodseats.

THE SOUTHPORT WIRELESSEXPERIMENTAL SOCIETY.

Hon. Treasurer and Sec., Mr. PhilipH. Christian, 9, Russell Road, South-port. This is a newly formed club,further particulars of: which will bepublished later.

THE BRISTOL AND DISTRICTWIRELESS ASSOCIATION.

Will intending members please notethat the address of the Hon. Sec., Mr.

FEBRUARY, 9,zo

Alan W. Fawcett, is 11, Leigh Rd.,Clilfton.

WANTED.

Wireless Clubs for Chelmsford,Brighton, Croydon, Birmingham, andEdinburgh. Those interested shouldcommunicate with the following gentle-men. Mr. C. E. Jackson, 3, SeymourStreet, Chelmsford; Mr. M. G. Foster,Sillwood House, Sillwood Street, Brigh-ton; Mr. A. F. Lake, 318, BrightonRoad, South Croydon.; Mr. A. H.Staples, Y.M.C.A., Dale End, Bir-mingham, and Mr. W. Winkler, 9,Ettrick Road, Edinburgh.

THE LIVERPOOL WIRELESSASSOCIATION.

Hon. Sec., Mr. S. Frith, 6, Cam-bridge Road, Crosby, Liverpool.

NEWCASTLE AND DISTRICT AMATEURWIRELESS ASSOCIATION

Sec., Mr. A. W. Bridges, 53, Grey -stoke Avenue, Jesmond, Newcastle -on -Tyne.

BARNSLEY AMATEUR WIRELESSSOCIETY.

Sec., Mr. G. W. Wigglesworth, 13,King Edward's Gardens, Barnsley.

OVERSEAS RADIO CLUBS.

Holland: The Nederlandsche Ver-eeniging voor Radio - Telegrafie.Official organ : Radio-Nieuws, vanAerssenstraat 162, den Haag, Holland.Membership : circa 1500.

United States: The MilwaukeeAmateurs' Radio Club. Secretary :Mr. Rudolf A. Teschan, 2319-2329,Wells Street, Milwaukee, Wis., U.S.A.

650

11111111111111111111111111111111111111111111111 III W111111111111111111111111! 1111111 i 1111111111M

.= The Proceedingsof the Wireless Society of London

ff-_- Ordinary General Meeting held in the Lecture Hall of the Institution E -of Civil Engineers, on Friday, December 19th, 1919. The President, -:-

Mr. A. A. Campbell Swinton, in the Chair.

The Secretary read the Minutes of thelast meeting which were duly confirmed.

THE PRESIDENT then referred tothe list of members recommended bythe Committee for election and nowput up for ballot by the meeting. Healso annpunced that three members ofthe Society had been transferred from

the grade of Associate to that of Mem-ber. Dr. J. Erskine -Murray thendelivered a lecture entitled " TheTransmission of Electro - MagneticWaves about the Earth," which wasfollowed by a discussion. The meet-ing adjourned at 7.30 p.m. after pass-ing a vote of thanks to the Lecturer.

THE TRANSMISSION OF ELECTRO-MAGNETIC WAVESABOUT THE EARTH.

By J. ERSKINE-MURRAY, D.Sc., F.R.S.E., SQUADRON LEADER R.A.F.

IN this paper 1 want to give you aresume of the state of our know-ledge of the conditions in the atmos-phere as regards the transmission ofelectrical waves. Most of our work

in wireless is, as a rule, on the actualinstruments themselves; but this takes usoutside, into meteorology and the physicsof the atmosphere. The atmosphere isnot very thoroughly understood, thoughgreat advances have been made recent-ly; but our knowledge is increasing,and, though it seems rather strange, wecertainly have in the past few yearslearned quite a lot about it from wire-less observations.

Now the first-for I am going toinflict upon you more or less thestory of the thing from the beginning-the first serious experiments ontransmission were made by the lateMr. Duddell and Mr. Taylor, whowas at that time a wireless officer in

the Post Office. I do not know thatthey were the first actual measure-ments but they were certainly the firstserious measurements; they consistedof observations of received current bymeans of the Duddell thermo-ammeterat a station ,near the pier of Howth, inIreland, near Dublin. The telegraphship belonging to the Post Office wasfitted with a spark transmitting set,and she sailed in various directionsfrom Howth, including a trip acrossto Holyhead. Fig. I shows by the fulllines the actual currents received atHowth when the ship was at certaindefinite distances, as she was crossingfrom Howth to Holyhead. Thereare two lines in the Fig., one showingthe received currents for 6o sparks persecond, and the other for 40 sparksper second. They are both the sametype of curve. The dotted line showsthe product of the received current and

651

Mem60441

.5

"bd

J ,


1 1

**Ilety' "Iprorp*==straZet'wate,Tussing Paircursco1a asdal. Him= r a. dusestar.

9."Irt'sre Ps6) tII "4Ye= tfros r1:114g. 6.1.moscp. i la dirmeer.

:EFry,_._istpc!!r.1/yew es 1.trrnry.erepeut dar and .,or =volution* per =nutr.

I

I

r- 1- - - - -

... G C.,. M.4 au 44 4 ..44 IO'_....

. T -trauma

al r....,

1 06,00-

P= "66. ss. .. . . .. .... u0-gyp 6 0 so as ,

Fig. i. Received Currents at Howth.

the distances between the receivingand transmitting stations. You willnotice that for a large part of the courseit is nearly a straight horizontal line,that is to say, that the received currentwas very nearly inversely proportionalto the distance. There is a slight dropas you get further away, indicating somekind of absorption. There is a very

Ship crossing from Hcwth to Holyhead.

I

650

5666

4600

0

1,060

curious hump between zero and eightmiles, which shows something quite dif-ferent-that is, there is some differencein the conditions for that portion of thecourse.

Fig. 2 is another diagram relatingto the same set. of experiments, inwhich the trip was in a slightly dif-ferent direction. It shows the same

ei

CI

ea6

;

4.1

Des.= Si res===== /.11 cm le=000011Paly iseImasays as se 012. 0 01. d010<10/.

.r"...... 00, 4-0.1 Idsr.. t............s.e..........s ,.....-s.r..,. 4 exPs .46P sus

U TrIly.',.,%".7,7,=====e cerp=,..,

span=we., ter=.11:==e per mm..

Y.004'.

LS -

v.»[mar900!...

44146

7..s.

-1s. . ....... SP60

......,.

Imp

1- --r--i-- r-7 -- ---.

?q.

...._

r-6.= 10.4, yvy Seryy6 " ' I Pes' Peoryl

1 6 00 14 4 rp6.121=6 beim. 1166.......

1.1. Ilacter 38 4* .4 **. *. * * * .e * *

Fig. z. Received Currents at Howth. Ship returning to Holyhead.

652

WIEFLESS SOCIETY OF LONDON : Transmission of E. M. Waves.

-features : the product of current intodistance is nearly constant from about-twenty miles to about sixty miles,which was right across the channel,but the hump is very much larger.'That is to say, between sixteen milesand the start, there was a very muchlarger current than would be expectedif it were proportional to the distance.That is for the ship returning.

Now I would like to show you whatI take to be the meaning of thesecurves. Fig. 3 shows the tracks of thevessel near Howth. For the firstthree miles or so on the outward trackthe signals were very much stronger

.F.g, 3. Useful portions of wave trains arrivingat Howth from various directions.

in proportion to those received duringthe remainder of the outward trip (Fig.t). The outward track went straightout from Howth pier, turned east-wards, and went on with a slight trendsouthwards. The dotted line in Fig.3 shows the direction of the vesselwhen she was twenty miles out on thecutward track, and seven miles out onthe inward track. Those were thepositions where the sudden transitionstook place-the product of receivedcurrent and distance, from being con-stant at one value, rose suddenly to a

higher value as Howth was approached.For the first, portion of the trackthe signals had to cross practically noland; after the vessel was about sevenmiles out the signals had to traversea considerable portion of the land be-tween the station and the eatstwardcoast. The lower shaded area on theFig. is supposed to represent thewaves which really got to the aerial.They scattered a +bit because the aerialhas a certain height, absorbs a certainamount, and there is a certain concen-tration. The parabolas bounding theshaded areas-they are approximatelyparabolas-represent the last parts ofthe series of waves arriving at the re-ceiving station, and it may be notedthat in the case of the inward track,very little of that area is on land(upper shaded area); in the outer track,about half of it is on land (lower shadedarea). This makes a difference. All theouter part of the journey of the waveswas over sea; but the tail -end recep-tional part had to pass over about amile and a half of land before it gotto the station. In the other positions,to the northward, there was no suchabsorption; in the positions southward,there was much more absorption, theproduct of current into distances beingstill smaller. This is a practical proofthat the ground resistance, especiallynear the receiver, is of much import-ance.

Other deductions which I made'from those experiments, showed thatthe actual loss by absorption and thedissipation during the day was equiva-lent to about 0.24 micro -amperes permile on a total of 126 micro -amperesat 6o miles. That is hardly a strictmathematical way of stating it but itgives a reasonable idea. During thenight the drop was only 0.025 micro-amperes per mile, just about a tenth.Obviously, therefore, there was more

653

THE WIRELESS WORLD

dissipation during the day than duringthe night.

The form in which the waves arriveat the receiving station is very import-ant. The effect of the ground or seais to bend back the wave -front by rea-son of the waste of energy due toground resistance. The result of thisis that the energy reaches the receivingstation not horizontally, but in a down-ward sloping direction. Hence it fol-lows that this energy must have beentransmitted in a direction sloping up-wards. The energy which leaves thetransmitting aerial in a horizontal di-rection is bent downwards and dissi-pated in the ground immediately Thusthe energy arriving at the receivingaerial is transmitted mainly throughthe upper parts of the atmosphere. Aseries of diagrams has been given byDr. Zenneck* showing not exactly theform of the waves but how the re-ceived voltage varies at a point asa wave passes it. These diagrams, byshowing the inclination of the maxi-mum received voltage under differentground conditions, indicate the direc-tion in which the receiving aerialshould be inclined in order to obtainthe best signals.

Fig. 4 indicates roughly the proper-ties of the atmosphere. The left-handscale gives kilometres of height. Thelower layers of the atmosphere are oxy-gen and nitrogen; higher up the per-centage of nitrogen increases; at about75 kilometres there is no more nitro,-gen but there is a little hydrogen. Apaper has appeared this month in thePhilosophical Magazine, in which Pro-fessor Lindemann discusses this ques-tion of atmospheric composition inconnection with magnetic storms anddisturbances. He rather doubtswhether there is much hydrogen there,partly from the fact that there is not

* Dr. Zenneck "Handbook of Wireless Telegraphy."

900

300 -

17

FEBRUARY, 1920

0.0017 100

Fig. 4. Diagram showing composition andpressure of the atmosphere at various hfights.

much to be seen of the hydrogen spec-troscopic line. The right-hand sideof this diagram indicates the atmos-pheric pressure, but this does not affectus much at the moment, except toshow that at the fifty kilometre lineyou have got a very low barometricpressure and therefore a place wherethere may be considerable conductivity.Fig. 5 shows to scale the curve ofthe earth, marked E, and above it thepart of the atmosphere which is con-ductive-not very conductive, butabout as conductive as very good cleanwater. This conductivity is confirmedfrom the known facts about vacuumtubes. At a pressure such as we getat 75 kilometres up there must be afair conductivity, especially if there isionisation, and, in the day -time, ionisa-

V

,00<7; ///' '

Fie. 5. A portion of the earth and atmosphereto scale. E = the earth; V = outer space, the -shaded parts are conductors, the strip between them

being the dielectric of Wireless Telegraphy.

654

WIRELESS SOCIgTY OF LONDON :

tion must be always present owng tothe ultra -violet light from the sun, iffor no other reason.

The first suggestion of a conductingsurface in the upper atmosphere wasdue to G. F. Fitzgerald, a well-knownIrish physicist who made the suggestionin 1893. Sir Oliver Lodge madesome experiments to ascertain whetherany oscillations could be detected, thatmight be produced by the concentriccondenser formed by the earth and thislayer. He could not find any suchoscillations: Heaviside introduced thesame idea into his article on " Tele-graphy " in the Encyclopedia Britan-nica-the latest edition-and Profes-sor Kennelly of America elaborated theidea somewhat later.

Now the next point that we cometo is the question of the variation be-tween day and night. This wasfirst noticed by Marconi in 1902.He had an installation on a ship, I thinkthe Philadelphia, going across to Ameri-ca, and by day he got good signals upto about 700 miles. By night he gotthem up to about 1,500 miles, or somesuch figure about twice as far at nightas it was during the day. That wasvery interesting, and naturally it wasput down at first to a possibly less elec-trically perturbed atmosphere duringthe night. This was therefore natu-rally connected with the ionisation ofthe air by daylight. Much experi-mental data began to accumulake short-ly after that; in particular, observations

A E

Transmission of E. M. Waves.

made by Mr. Edwards, head of theCanadian Government wireless service.A great many observations were pub-lished of long distance transmissionduring the night, or " freaks," as theywere called. I put those all togethersome 'time ago, and found that it didnot matter in which direction youwent, or what wavelength was used,these unusually long transmissions couldbe effected on many nights in the year.

The particular case which seemed tomake it perfectly clear that this wasdue to reflection from the upper layerwas one in which there were threestations-Victoria in British Columbia,on Vancouver Island, Pachena Head,on Vancouver Island, about 75 milesaway, and a place on another island,called Ikeda Head, four hundred milesaway. (Fig. 6.) Victoria transmits toPachena Head during the day and dur-ing the night equally well, but alwayswith some difficulty (there is somelocal difficulty). Victoria can be heardat Ikeda Head almost every night,but never during the day. If youassume your upper conducting layer asat AB, to act as a reflector during thenight, the above is easily explained.Signals from Victoria to reach PachenaHead by reflection from the layer AB,would strike it at the large angle 0.This is not favourable for reflection,especially as the layer is by no meansa perfect reflector, but is like the reflec-tion from water or glass. A great dealof the energy will go through. Inorder to reach Ikeda Head, the waves

I P

400MILES .1

Fig. 6. Diagram of transmission between Victoria, Pachena Head and Ikeda Head Stations.

655

- 0.0015d/-NIa.

THE WIRELESS WORLD FEBRUARY, 1920'

will have to strike a point E about 200miles away. They will graze the sur-face at the small angle q and the reflec-tion will be good. This explains thefact that signals are received at IkedaHead during the night, and not duringthe day-whereas the night makes verylittle difference to the communicationsbetween Victoria and Pachena Head.Many other instances could be givenbut this is a particularly good one.

Now I would like to mention Dr.Austin's measurements of the energyreceived at considerable distances oversea by day. He carried out a great manyexperiments, from the results of whichhe deduced the following well-knownformula :-

I, =4.25IGJz1h2

where Ir = Received current (amperes)I. = Sending current (amperes)111= Height of sending aerial

(kilometres)1z2= Height of receiving aerialX = Wavelength (kilometres)d=Distance between stations

(kilometres)It shows the relation between the

received aerial current and the trans-mitting aerial current, the distance andthe wavelength. It includes a factorfor dissipation, that is to say the lossof energy en route. It is interestingto note that Dr. G. N. Watson pub-lished only a few months ago a math-ematical paper in which he shows that alayer of ionised air having a resistanceof 6.95 x Pos ohms per centimetrecube, and a height of about Poo kilo-m'etres, will give just the same resultsas Austin's formula. We have now,therefore, a theory for the Austinformula. This all goes to show withalmost mathematical certainty the exis-tence of this ionised layer.

Of course it is not actually a case ofreflection in the day -time; it is not a

purely reflecting layer. In the day-time it is rather a case of refraction andappears to conform to the explanationwhich Dr. W. H. Eccles has given ofthe bending of electromagnetic wavesin their passage from a layer ofless to a layer of greater ionisation.Fig. 7 gives an idea of what happenswhen the sunlight strikes the earth.On the left hand is the dark side. Thearrows represent the sun's rays. Theirregular part of the lower boundary onthe right of the layer OPQR is meantto indicate that the ionisation is coming

-NN\ \\\\\Fig. 7. Effect of daylight on transmission,CAB = earth; OPQR = conducting layer;AD = line dividing sunshine above from

darkness below

down nearer to the earth's surface.Towards the left, that is, round to thenight, where there is no sunshine, theionisation dies out and the layer rises,and a clean, sharp reflecting layer isformed at that part.

Many interesting observations werecollected together in a paper in theProceedings of the Institute of RadioEngineers, and show the variations ex-perienced at sunrise and sunset. Dr.Kennelly and others have pointed outthat these variations may be due to theapproach of that irregular part indica-ted on the right-hand side of Fig. 7,where the transition from darknessto sunlight takes place. Here thereis, as it were, a reflecting wall of ionisedgas, which will throw back..the signalsand disturb them in some way or other.The sudden dips at sunrise and sunsethold practically uniformly for stationsin temperate climates.

656

WIRELESS SOCIETY OF LONDON

Now I come to the work of Dr. DeGroot. He has been acting for thelast nine or ten years as chief wire-less telegraph engineer to the Nether-lands Government in the East Indies,and he has had there an opportunity ofstudying many things which we do notget a chance of studying so well inthis country.

Fig. 8 provides a definite proof that thereflecting layer actually exists, and thatits height in the tropics is about 180 km.The proofs I have shown so far aresatisfactory to most people, but thisproof cannot be got round in any way.S represents Sabang on the not)th-westpoint of Sumatra. 0 is Osaka, inJapan. There is about 6,0oo kilo-metres between the two. Sabang isonly a five kilowatt station and, inordinary circumstances during the day,could not be heard above 15o miles.But at the place marked J, which isnear Java, S can be heard quite nicelyat night. It cannot be heard again atgreater distances until Osaka is reached,where it is frequently received at night.That is a clear proof; there is no otherway by which the waves could get fromS to 0 without touching P and Q,except by reflection; and, since theywere very short waves, and since lengthof waves-as he afterwards proved --made no difference, it clearly must bea matter of practically pure reflection-reflection from a surface that is apretty good reflector. Later experi-ments show that these maxima occurevery 3,000 km. right round the dark

Ref I ec ti ng

Layers

PATH


side of the globe, if the transmittingstation be a large one, six maximaoccurring between the station and itsantipodes.

Fig. 9 is simply a theoretical. dia-gram showing roughly how energywaves from a source S would be re-flected from a semi -transparent surfaceAB. It will be seen that if the wavesstrike the surface AB at a large angle 0,as at SCD, that most of the energy goesthrough; if they strike at a smallerangle 0, as at SEF, some of the energyis reflected down, as at EG; if theystrike at a still smaller angle all theenergy is reflected. SHK is the angleof total reflection.

0

Fig. 9. Reflection of energy at a semi -transparentsurface.

We now come to 'the most interest-ing part of De Groot's work, whichreally does throw a good deal of light,when properly understood, on the ac-tual atmospheric conditions. Fig. 10shows a series of measurements ofstrengths of signals. The ordinatescale is not actual signal strength, butthe values of the shunt resistance con-nected across telephones-the greater

OF WAVES

////////1///6000K

Fig. 8. Diagram of transmission from Sabang.

657

180 KM

0

100-

0

100

0

THE WIRELESS WORLD

24JUNE 1914

FEBRUARY, 192o

5 6 7 8 9 to II

15 JU LY14

6 7 8 9 10 11

?1 21 ;SEPT'1315 \SEPT'14

10 .1 ik1 it /

1 2 3 4 5 6 7

26 MARCH'14100

2 3 4 5 6 6 7 9 10 11 1 2 3 4 5 617 APRIL114

12 3 4 5 6 6 7 8 9 lo 81

20M ARCH'14.:

G 7 8 9 10 11 1 Z3156 7 8 9 e0

1 2 3 4 G

II 1 2 3 4 5 G

Fig. so. Series of Signal Strength Measurements.

this resistance, the weaker the signal.Thus the peaks of the curves representabsorption. Generally speaking, it willbe seen that in June, during whichmonth the sun is lowest in these regions,there are four comparatively small ab-sorption maxima. As the height ofthe sun increases from month to monththese peaks increase also as the diagramshows. The full line relates to trans-mission in one direction between two

islands about 1,000 kilometres apart.The transmission in the other directionis shown by the dotted line; it is of asimilar character but not quite thesame. The most interesting part ofthe picture is for those months in whichthe sun is nearly vertical. There isenormous absorption at two peaks, oneon each side of mid -day, and two otherpeaks about eight in the morning andhalf past four in the afternoon. The

658

WIRELESS SOCIETY OF LONDON:

little sunset and sunrise effects whichfigure so much in this country prac-tically disappear altogether. Thereis a big variation at 4.30 a.m., whichis an hour and a half before sunrise.The minimum of absorption about themiddle of the day does not alwayscome at noon exactly. Sometimes itis a little bit on the afternoon side; atother times of the year it comes a littleon the morning side. Evidently thewhole thing has some perfectly definiterelation to the position of the sun, andthat is the important point about it.

De Groot has actually worked outthe principles of these relations. Fig.II is his diagram illustrating whathe thinks happens. I may put it thisway : during the day the way in whichthe energy gets from Sitoebondo toKoepang and Amboina-two places,one 1,100 and the other 1,700 kilo-metres away-is clearly through someupper part of the atmosphere. Thisis for two reasons, firstly, as we haveseen above, the energy that leaves thetransmitter horizontally is always ab-sorbed by the earth's resistance, andtherefore the energy that actually getsto the receiver must have left the trans-mitter in an upward direction; second-ly, these daily variations, since the suncannot be imagined as producing largevariations in the resistance of theearth's surface. I do not say that Stheenergy is reflected because during theday the quantity of energy which getsfrom the one place to the other dependson the wave length. This points toionised layers refracting the waves asthey pass from one layer to another.

C

SIT.KV%Strongly

Ionised Layer


The diagram does not show all thewaves that are leaving this sending sta-tion; it is simply drawn in order to showthat for waves to arrive at the distantreceiver they must have started at theangles indicated, because if they did notdo so they would be deflected down tothe earth again as at T and A'. Itshould be remembered that the peaksin Fig. Io were perfectly definite andfairly sharp; they started up in halfan hour and went off again in half anhour, which shows that there is notjust one layer of ionised air, but layers.This coincides with our knowledge ofvacua; the vacuum tube as it is ex-hausted does not slowly increase inconductivity, it goes in jumps dependingon the sudden formation of ions atcertain definite pressures.

De Groot found that there werecertain definite relations between thesun's position and the formation ofthese maxima of absorption. He foundthat whenever the sun was verticalover one or other of four great circleson the earth, the absorption was great-est. Fig. 12 is a somewhat complexlooking diagram, but it is a wild at-tempt to draw planes through greatcircles and small circles. E is theglobe, SP is the south pole, and PP is thepath of the sun through NV/IVY/V.Over that small circle of the earth thesun is vertical on some particular day-remember those stations-marked S andK-are. between the tropics. Thegreat circle through the stations ismarked on the diagram. Whenever thesun is nearly vertical over the points

KOEP1100 ---)41700

AM8

Fig. ti. Refraction of Energy at Ionised Layers.

659


Plane throughpath of waves

Great Circlethrough S tioN

Fig. I2. De Groots's diagram to illustrate his Theory.

W', Xi, I", or V, there is a maxi-mum absorption. For another day inthe year these points might be furtherup on the four fixed great circles-A,B, C, and D. They are at rightangles to the line of transmission(great circle) between the stations anda definite number of degrees away fromit-B is twenty degrees east, C twentydegrees west, D forty degrees west, andA forty degrees east. This shows thatthere is a definite relation between theheight of the sun and the absorptionof the energy of the waves in passingfrom one of these stations to the other.The plane through the path of thewaves is shown shaded, and the darkershaded portion is the path of thewaves from station to station. DeGroot raises the question : What canthe relation be between the verticalityof the sun on this spot of earth and

Equator

the amount of absorption of energyfrom a wireless signal passing from Sto K? There is this fact; those greatcircles on which the sun is vertical atmoments of maximum absorption areperpendicular to the path of the waves.He asks further : What is the onlything that can be affected ? It mustbe the path of the waves itself.

Let us draw a plane W, parallel to thegreat circle A which passes through Wt.The light of the sun is coming downin that plane, and it cuts the path ofthe waves as _indicated. For one ortwo days in the year the sunlight willactually come down the centre line ofthe plane and be in the plane of thewave path itself; at other times it willnot come down the centre line but willstill be at right angles to some otherline which starts from Koepang andrises in the upper atmosphere, and De

660

WIRELESS SOCIETY OF LONDON

Grqpt says that this line is probablythe path of the actual waves, and thatthe fact that the sunlight is comingdown at right angles to the path of thewaves is in some way or other a causeof the absorption. Similarly for theother planes X'Y'Z' later in the day.The plane X corresponding to the posi-tion of the sun over Xi should be atright angles to another part of the wavepath. The sun's rays come down atright angles or some definite angle-hesays a right angle-thus there is a defi-nite relation between the direction of thesunlight and the absorption, which pro-bably arises from a definite relationbetween the sunlight and the path ofthe waves rising from the one stationand descending to the other.

I will conclude with one or twosketches showing what sort of relationDe Groot thinks may actually exist.He suggests, of course, that it is prob-ably a variation in ionisation; that isundoubtedly the only thing which wehave got in the conditions which canvary. Taking mid -day as being thesimplest to begin with (Fig. 13);suppose we consider AB to be the sur-face of the earth, while S is the stationSitoebondo and K is Koepang. Thesun is vertical There is no want of

SUNLIGHT


symmetry, so that there should behorizontal layers of ionised air, theupper ones no doubt being more ionisedthan the lower ones. Of course, fur-ther up there will not be enough sir toionise, but immediately above theearth, up to, say, sixty kilometres crso, there will be progressively increas-ing ionisations with, as far as we know,comparatively sharp boundaries betweenthe layers. In order that the wavesmay get from S to K they must havetravelled somewhat as indicated. Atmid -day there is not any particular ab-sorption; the waves make a symmetricalcourse, do not go very high and comedown to the station in about as shorta way as they could reasonably do.

Take another case, for about nineo'clock in the morning. (Fig. 14.) ABis the surface of the earth; S is Sitoe-bondo, K, Koepang. The arrows indicate the direction of the sunshine.The ionised layers will be bent downsomewhat as shown. The cause ofthis bending may be seen by referenceto Fig. 15 which diagramatically illus-trates the shape of the conducting shellround the earth as modified by theeffect of the sunlight. The questionarises : How are the. waves going toget from one place to the other Re -

PATH OFWAVES

// / ///////// ///// / ///S K

Fig. 13. Refraction of Energy between Sitoebondo and Koepang (noon).

661

IONISED

1..AYERS


A ////7 //

IONISED

LAYERS

Fig. 14. Refraction of Energy between Sitoebondo and Koepang (lo a.m.) looking North.

ferring again to Fig. i4, let us con-sider a wave at an angle of about forty-five degrees (as in the case of Fig. 13)to begin with and see where it goes.It goes from K, probably reaches C,gets refracted from there, and goesaway between the layers towards D,and is lost. That is the direction of theradiation from the aerial whichreached the receiver at mid -day (Fig. 13)but now it no longer gets there.The wave that is going to get to S,starts up at a much bigger angle, some-thing like KE-that is a much weakerwave than the first one, because thereis very little energy radiated verticallyfrom an ordinary aerial. KEFG isthen the wave that is going to reach' Swhen the layers of ionisation areas shown. If the diagrams for othertimes in the day were drawn we shouldfind possibly a real explanation of theseextraordinary daily variations. 1 maypoint out one fact, that during tIle timewhen the sun is comparatively low atmid -day, in the cooler season in fact,De Groot obtained sunrise and sunseteffects comparable to those of Europe.During the time when the sun is nearlyoverhead-from November to January-sunset and sunrise effects disappear

almost completely, and these hourlyvariations become very marked.

Most of the foregoing account ofDe Groot's experiments I have takenfrom Dutch publications, and in par-ticular from De Groot's " Radiotele-grafie in de Tropen." 1 hope 1 havebeen able to throw some light on the

sualighr

10a rn k I * p. ',positionZ. z

Ionised sk'kTOP OLayersArmosph e re

:Ns1

Fig. 55. Distribution of Ionised Layers roundthe Earth, looking Northwards.

subject, and that you will now be ableto follow wha,t is going on in this par-ticular branch of radio work.

DISCUSSION.The PRESIDENT said he had intended to

call upon Professor Howe to open the dis-cussion, but as the latter had left the meet-ing he would call on Admiral Sir HenryJackson.

662

WIRELESS SOCIETY OF LONDON : Transmission of E. M. Waves.Admiral Sir HENRY JACKSON : Mr. Chair-

man. and gentlemen, I do not feel qualifiedco discuss the paper, but I should like tocongratulate Major Erskine -Murray on it.He has put a very difficult question extremelyclearly, and I think that anybody who hasfollowed his explanations will now go awaywith some good clear idea of how it all hap-pens. It has puzzled many of us, I expect,at various times. I have never studied theseeffects to the extent that he has done, andI go away very much happier than I camein. I must congratulate him on the paperand the way he has put it; evidently therehas been a very great deal of work involvedin getting the results out from Dr.de Groot's theory. I leave it to more techni-cal people to discuss some of these mattersas regards the ionisation of the atmosphere,and the distance the ions can penetrate. Ido not profess to know myself, but somebodyelse can perhaps enlighten us. I think wecan all agree that we owe a very hearty voteof thanks to Major Erskine -Murray for hislecture.

Mr. PHILIP COURSEY : I do not think I canadd much useful discussion to the very luciddescription that Major Erskine -Murray hasgiven us this evening. It is very useful foreveryone to have such descriptions of experi-ments that are going on at the present time,especially when they are published in foreignlanguages, and in publications such as Gov-ernment ones, which a re not accessible toeverybody. I think we must all thank MajorErskine -Murray very much for giving us thisexcellent description.

Mr. MAURICE CHILD : I noticed that Dr.Erskine -Murray mentioned the fact, on thequestion of absorption, that freak communi-cations took place in all parts of the worldand at all sorts of times. From enquiriesthat I have frequently made from variousoperators on ships at sea, I have generallyhad the information given to me that inEurope the longest distances in which onemight say that freak communications tookplace were generally in the direction of northand south ; that no great distance in Europeseems to take place when the signalling iseast and west. I do not know whether Dr.Erskine -Murray can give us any informationabout that?

Mr. J. SCOTT-TAGGART : I would merely liketo add a word of appreciation to the excellentpaper we have heard to -night, and, perhaps,to ask Dr. Erskine -Murray to let us havesome of the practical details of the methodsby which these observations were taken. Itwould be interesting to know, furthermore,what form of detector was used. I under-stand that the parallel resistance method wasemployed, and so it was essential that someform of constant method of detection shouldbe used. It would be interesting to knowexactly what type of detector was used, andwhat means were taken to maintain its con-

stant action. I think the subject is of con-siderable importance to us at present, sincemost of us are now able to receive messagesfrom America, and these problems of ionisa-tion effects concern us all and not merelythose in charge of the higher power stations.Consequently we all look forward to seeingthis paper in print, when we shall have a bet-ter opportunity of studying it in detail.

A MEMBER : I should like to ask Dr. Er-skine -Murray one thing with regard to direc-tional wireless at night ; surely there is a cer-tain amount of electrical turbulence? If youhave got a station whose direction you thinkyou know in the day time, at night it mayappear to move in a clockwise direction orcounter clockwise direction. You get extra-ordinary variations in a very short time in-deed ; I should say that is possibly due toclouds of ionised gas, or something like that.

Lieutenant HALL : I should like to ask Dr.Erskine -Murray to explain if possible the ex-traordinary freak transmission in the presenceof the northern lights. I have noticed mostclear examples in Canada ; coming down theRiver St. Lawrence on one occasion stationswith only half a kilowatt communicated withplaces as far distant as San Francisco. Whenthe northern lights disappeared the stationsresumed their normal range.

Mr. W. H. SHORT : Dr. Erskine -Murray hasshown us the diagrams of the variations of thesignal -strengths for certain months. I takeit those diagrams are compiled from a, wholeseries of diagrams taken on consecutive days.There is a gradual change in the position ofthe peak from the start of the month to theend of the month ; I should like Dr. Erskine -Murray to make that clear.

The PRESIDENT : If no one else wishes tospeak I would like to add the thanks of themeeting to Dr. Erskine -Murray for his ad-dress. I came into the room knowing no-thing about the subject at all, but I certainlyfeel that I know a little more than when Icame here. I take it that is the raison d'Ureof this Society. We are all anxious to learn.We are in a rather different position fromwhat we were before the war, because wehave now got a certain number of memberswho know a great deal, whereas others of usknow a very little. We are hoping we shallgradually get those who know to impart theirinformation to those who do not.

Dr. J. ERSKINE-MURRAY : In regard to thepoint that Sir Henry Jackson raised as re-gards ionisation, I do not think there areany real figures in respect to the upper atmos-phere. A great deal of theoretical work hasbeen done, and the latest I have seen is thepaper of Dr. Lindemann in the PhilosophicalMagazine, which gives most of the availablefacts-or approximate facts, may I sayabout the upper atmosphere.

As regards north and south freaks,I do not think that there is reallyvery much in this, except perhaps

663

THE WIRELESS, WORLDnear sunrise and sunset. Near sun-rise and sunset when the shadow wall iscoming along, in all probability there is bet-ter transmission north and south than acrossthe shadow wall but if you were to take themiddle of the night, or the middle of the day,you would find freaks going pretty well inall directions. In America the commonestfreaks, I believe, are across the continent-that is, east and west. The common directionof freaks is very often simply the commondirection of a particular station. A manthinks, for examplp, that he usually hearsfreaks in a particular direction because heusually hears Aden ; but if there was anotherstation in the middle of the Indian Ocean hemight get the freaks from there just as well.Except for the shadow wall, I do not think thenorth and south direction has any serious rela-tion to the direction of freaks.

The detector which Dr. de Groot used was,I believe, a very carefully constructed crystaldetector. He had several, graduated them,kept them in very good order, and used theshunted telephone method for the measure-ment of signals. Measurements were madeday after day, but the actual curves which yousee were for particular days-since the curvesvaried from day to day. One curve was givenwhich was an average for the month. Theheight of the sun varies from day to day, soit was more scientific to retain the observa-tions of particular days instead of averagingthem. Most of the curves were for a definiteday, but observations were taken daily, andconfirmed that from day to day there was aslight difference in the magnitude and posi-tion of this maximum of absorption.

As regards " D.F." at night, I did notmean to give the impression that the upper

FEBRUARY, 1920

reflecting layer is a beautiful smooth sphere.A very slight difference in the direction inwhich the under surface of the upper layeris reflecting would make a very great differ-ence in the way in which the waves wouldstrike any receiving aerial. The explanationof those variations of apparent direction atnight may very likely depend upon the factthat the upper layer is not a perfect sphere. Ithink it is also most probable that some ofthem may be due to refraction. I pointed outearlier in the paper that Dr. Zenneck showedthe energy of the wave was first in one direc-tion, then up to a maximum nearly vertical,and then down in the other direction, so thatyou had always a turning field at every station,and more at some than at others, dependingupon the nature of the ground.

I think there is no doubt about what Mr.Hall said about the aurora giving freak dis-tances. The aurora is certainly an electricaldischarge in the upper atmosphere, which isextremely well ionised and acts as a very finereflector. I think there is no doubt aboutthat, because of the work that has beendone alike on the aurora and on wireless.Those are all the points that have beenbrought up, and I thank you for your appre-ciative attention. I know the subject is moreor less a special one, and I hope in future youwill.be inclined in this Society to make some-thing of it, because it is the, kind of thingthat private observers on wireless can do. Youcan perfectly well go on observing all nightif you like. With telephone and ordinary shuntresistances you can observe from day to day.But I do not raise your hopes that you willfind these wonderful regular peaks ; they aredifficult to find because you are not in thetropics.

AIVIATELJEZSIf you wish tofavourite hobby,

enjoy a maximum of freedom to pursue yourand to win for amateur wireless a fitting status,

JOIN A CLUBHELP A CLUBSTART O?: CLUB

FOR ASSISTANCE OR ADVICE, WRITE TO THE EDITOR.

664

it

J111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111E:

Aircraft Wireless SectionEdited by J. J. Honan (late Lieutenant and Instructor, R.A.F.).

These articles are intended primarily to offer, as simply as possible, someuseful information to those to whom wireless sets are but auxiliary" gadgets " in a wider sphere of activity. It is hoped, however, thatthey may also prove of interest to the wireless worker generally, asillustrating types of instruments that have been specially evolved to meet

the specific needs of the Aviator.

SHORT-WAVE TUNER, MARK III. (Continued).

THE AERIAL CIRCUIT. Stud

As shown in the schematic diagram,given in Fig. 26, this circuit comprisesthe aerial variable tuning condenser, vari-able tuning -inductance, and earth.

The condenser is of the movable -vanetype with aluminium plates and air di-electric. It is graduated in degrees fromo-180° and has a maximum capacity of0.0015 mfds.

The inductance consists of seven -stranded wire wound upon an horizon-tally -mounted drum from which non -inductive leads are taken to 19 studs,giving the following values :-

Stud I = 6 mhys.2= 12.2

11

3= 20.54= 30.65= 40.6

53.2-7= 6748= 83.59= 97.5

10=112.311=126.312=143.813=158.214= 1776)5=195.0

,,

16=213.4 mhys.17=230.818=250.010=280.0

The earth is preferably of the capa-city type consisting of one or more cop-per -gauze mats spread out on the sur-face of the ground. Both the aeriallead-in and the earth lead should be asshort as possible, the former being wellinsulated and the latter of stranded low -resistance wire.

THE CLOSED CIRCUIT.The variable condenser is of similar

design to that contained in the open cir-cuit, but has a maximum capacity of0.0005 mfds.

The stranded - wire inductance - is

wound on a drum of the same size asthat used for the aerial inductance, andhas five tappings, giving the followingvalues : -

Stud I= 13.5 mhys.11 2= 23.5 )5

I) 3= 404=115 11.11

1) 5=28oThis drum is also mounted horizon -

'tally, but is rotatable about a perpendicu-

665

TfAIN

lar axis so as to increase or diminish itsmagnetic linkage with the open -circuitcoil, and thereby vary the inductivecoupling between the two circuits. Thisis controlled by means of a handlemounted on the axis of the drum andbrought out to the ebonite face -plate ofthe set.

THE DETECTOR CIRCUIT.As shown in Fig. 26, either the Peri-

kon or carborundum can be placed inseries with the phones at will by meansof the " crystal " switch. As a generalrule the carborundum crystal is morestable than the Perikon, though the lat-ter is more popular in use as no potentio-meter adjustment is necessary.

It is advisable to test the Perikon fromtime to time with the buzzer, readjust-ing the contact point between the twocrystals when necessary. Sometimes itis impossible to get satisfactory resultswith any contact point, in which casethe crystals are probably "fatigued" andshould be replaced by fresh ones. Inall cases a light contact -pressure shouldbe used. A forced pressure gives poor results, and, moreover, shortens theeffective life of the crystal.

THE WIRELESS WORLD

Perikon

Carb

SWI Tell

FEBPU AR Y , 1920

Fig. 26.

The potentiometer circuit used withthe carborundum is fed from a batteryof four dry cells giving a potentiometerdifference variation of + 3 to -3 acrossthe crystal. The potential applied isadjusted by means of a handle whichcontrols the position of the variable pointalong the rheostat. A switch is providedto open the circuit and save the cellsfrom running down when the potentio-meter is not in use.

The two pairs of high -resistancephones (4,000 ohms. per earpiece) areused in parallel and are shunted by asmall condenser which is inserted in or-der to compensate for the lag in the pas-sage of the signal current caused by thehigh inductance of the telephonewindings.

The detector circuit as a whole isthrown on stand by " or " tune " posi-tion by means of the main change -overswitch.

CALIBRATING THE CIRCUITS.The buzzer is also used to calibrate

the open against the closed circuit withthe object of securing rapidity and accu-racy in tuning -in.

The closed circuit is first tested against

666

AIRCRAFT WIRELESS SECTION.

a wavemeter for varying wavelengths,the results being recorded, so that a de-finite series of wavelengths correspondsto ascertained values of closed-circuit in-ductance and capacity.

Corresponding values of open -circuitinductance and capacity are then ob-tained by tuning the open circuit againstthe known wavelengths now emitted bythe closed circuit, when set at the pre-viously recorded values of inductanceand capacity and excited by means of thebuzzer.

This series of results is tabulated ona calibration card so that when a signalis first received on " stand by " the opera-tor will be able by rapidly noting theopen -circuit condenser and inductancereadings for maximum sound and com-paring them with his calibration cird,not only to ascertain the signal wave-length, but also to set the closed-circuitcondenser and inductance to the correctvalue before switching -over to the" tune " side, thereby obviating the riskof losing weak signals when changing -over.

Though involving a certain amount ofintial trouble, the calibration card wasfound in practice to be most useful, pa --ticularly in the case of operators whowere " learning the ropes."

THE SHUNTED BUZZER.The buzzer itself, as shown in Fig.

27, is shunted across the poles by a ninductive resistance S. This affords adischarge path for the high e.m.f. in-duced across the armature winding wheneach " break " occurs, and prevents aspark discharge between the points,which would in effect prolong the cur-rent and so lessen the inductive impulseapplied to the oscillatory circuit L.C.

In addition, whilst the contact pointsare closed, the shunt is in parallel withthe high -resistance of the solenoid andthereby allows a higher value of current

Fig. 27,

to pass through the points. As the mag-netic field created about the inductanceL increases as the square of the current,the extra current passed by the shuntconsiderably increases the vigour withwhich the buzzer energises the oscilla-tory circuit L/C.

Though forming but a comparativelyunimportant detail of the tuner, it is aswell, perhaps, to have a clear conceptionor the exact significance of the "shuntedbuzzer," as owing no doubt to the an -pealing qualities of the name itself it isfrequently and widely applied by ex-perts and others in a sense which, to putit mildly, indicates a regrettable lack oftechnical precision.

667

-,H11111111111111111!1!11111111111111111i1111111111111111111111111111111111111111111111111111111111111L2

Aviation Notes=d1111111111111111111111111111111111111111111111111111111111111111111111111111111IIIIIIIIIIIIIIIIIIIIFI:

PIONEERS OF THE AUSTRA-LIAN AIR -WAY.

THOUGH lacking thedramatic elements associ-ated with the transatlan-tic flight, the achievementof the brothers Ross in

linking Australia to the Mother Coun-try by way of the air will probablytake equal rank in the annals of Avia-tion with the exploit of the late SirJohn Alcock, of heroic memory, andhis gallant comrade.

The outstanding merits of the Aus-tralian flight are to be found as muchin the intrepidity and endurance ofthe airmen, as in the triumph. of

Photo:

constructive design and workmanshiprepresented by the machine and itsengines.

It may, of course, be argued that theflight, which was largely an overlandroute, became theoretically possibleyears ago-in fact, directly machineshad been designed capable of spanningthe relatively short water distancesinvolved. This is true, but it impliesthe existence of the necessary groundorganization, .and also of an unlimitednumber of relay machines and flyingpersonnel.

The great difference, however, thatexists between these assumptions andthe actual accomplishment of a flight

The Vickers-Viray Machine.

668

Photo Press

E

1AVIATION NOTES.

Mark VIII engines, giving a maximumspeed of zoo miles per hour. Itweighed 3 tons when empty.

The route from Hounslow touchedLyons, Pisa, Cairo, Damascus, Busra,Karachi, Delhi, Calcutta, Rangoon,Bangkok, Singapore, Bima, and thenceto Port Darwin. It is unnecessary tochronicle the misfortunes that attendedthe attempt to continue the journeyacross' Australia, and its subsequentabandonment, since the object of thetrip had been accomplished and theprize of £io,000 won when Port Dar-win was reached on December loth.

Photo: Photo PressCaptain Sir Ross Smith. K.B.E., M.G.,

D.F.C., A .F.C.

of 11,30o miles within a period of 28consecutive days by a single machinedriven throughout the journey by thesame pair of engines and carrying acrew of four, is just the measure of thesolid progress that has been made, andequally constitutes a criterion of thecredit that is due to the performance.

The King has conferred the honourof Knighthood of the British Empireupon both the pilot and his gallantbrother in recognition of the valuableservices rendered to aviation by theirachievement. His Majesty has alsoapproved of the award of a bar to theAir Force medal in the case of Sergt.Shiers and Sergt. Bennett.

As regards the craft, the laurelleaves again go to the Vickers-Vimymachine and the Rolls-Royce engine.The machine, of which a photographis given, carried two 35o H.P. Eagle

PAYING THE TOLL.Unhappily a heavy tribute was

exacted before the new air -way hadbeen traversed. It is said that the old.

Photo : Photo Prsse.Lieut. Sir Keith Macpherson Smith, K B.E.,

late R A .F.. .

669

THE WIRELESS WORLDcaravan routes across the Sahara arebrazed with the bones of those whohave fallen by the way. Similarly agrievous toll of life has been levied bythat Arbiter of the Air who guards itsways and appears to view each freshencroachment of his kingdom with ajealous eye.

We have to deplore the loss to theworld of.Aviation caused by the crashingof the Alliance " Endeavour " but afew minutes after starting out on thesame journey, resulting in the deaths ofLieut. Roger Douglas, M.C., the pilot,and of Lieut. J. S. L. Ross, his navi-gator.

Another tragedy to be recorded is

that of the Martynside Rolls machinewhich was wrecked off the Island ofCyprus whilst en route to Australia.No trace ' remains of Captain C. E.Howell, D.S.O., M.C., D.F.C., andAir Mechanic Frazer, who formed its

Photo : Photo Press.Sergeant J. M. Bennett, A.F.M.

670

FEBRUARY, 192(

Photo: Photo Press.

Sergeant W. H. Shiers, A.F.M.

crew. Apparently the machine wasforced down whilst over the sea byshortage of petrol, and became a totalwreck.

CORRECTION.

In Aviation Notes for December itwas stated that the R38 was undercompletion by Messrs. Vickers. Thisof course should have read Messrs.

Short Bros., who are the builders notonly of the R38, but also of her sisterairships.

Illim1111111111111111mmum11111111111111111iniim1111111111111111u,=

± Notes on the Design and Construc-Ition of Valve Amplifiers

BY JOHN SCOTT-TAGGART, M.S., Beige E., A.M.I.Radio E.

III.-DETECTOR-AMPLIFIERS (Continued from December).

MA.RCONI'S WirelessTelegraph Co., Ltd.,have evolved a numberof interesting amplifier -detectors, and as they

are of the class immediately under con-sideration a short description of theirtypes will not be out of place.

Fig. 12 shows type 55A. It employsseven valves in cascade, the first six ofwhich are high -frequency amplifiers andthe last one a rectifying valve. Theamplifying vacuum tubes are of the V24type, where- the last valve is of the` Q " type. The " Q " valve differschiefly from the V24 in that its grid is of

0Tev'efahon

0

+0H.T.-0-

+061e

G

metal gauze, whereas the grid of theV24 takes the form of a spiral wire.

In order to obtain efficient receptionover a wide range of wave -lengths, theaperiodic inductance coils are woundwith resistance wire to increase thedamping effect. In the case of type 55A,the resistance of each coil is 24,000ohms.

The output circuit of. one valve iscoupled to the input circuit of the nextin two ways. There is the ordinarymagnetic inductive coupling, and alsoa form of resistance coupling. There isin series with the anode of each valve ahigh resistance, and when the anode

nt-

WA/iftrfivs Con/O.45 ...5-cveem, ecx.r

Fig. I2.

671

0--cp.ke,es

0

+0KT-0

6V

Telephonere12/1,4,711Q

E0 CDCD 0

THE WIRELESS WORLD

. Ni=5";\%W=i8 KEE* *SEM .N.SESV 55"A

FEBRUARY, 1920

VV24 V24

VVVV

...rpe,;,, Coe.,yBor

V24.

Potan/rooler/i,

l'Amivvv!vwvv,

Fig, 13.

current is flowing there is an appreciablepotential drop along this resistance. Bymeans of the condenser connected be-tween the transformer windings and thecapacity between the windings them-selves, variations of this voltage dropcaused by incoming signals, are com-municated to the grid of the next valve.

The receiving oscillatory circuit is

connected across the 'terminals A and B.A potentiometer is arranged, as shown,to vary the potentials of the grids of theamplifying vacuum tubes, in order thatthe most suitable operating point maybe found. The telephone receivers areconnected through the intermediary ofa telephone transformer to the plate cir-cuit of the detecting valve which, it willbe noticed, does not operate on theleaky grid condenser principle, but be-cause of the asymmetry of one of thecharacteristic curves of the valve. Aselector clip enables any number ofvalves up to six to be used.

Type 55A works best on a wave-length of 1,000 metres, but will receivesignals efficiently on wave -lengths be-tween 500 metres and 3,000 metres. It

TniARod

chp

q II

V.24

Pio/eat,Copoci6i Reocrn.

is interesting to note that the sensitivityof these amplifiers falls off rapidly forwave -lengths below the optimum value,but only slowly in the case of longerwaves. As will be seen from Fig. 12,a retroactor coil (or reaction " coil)may be coupled to any of the trans-formers to produce retroactive amplifica-tion or self -oscillation when continuouswaves are to be received. This may bedone by removing the connecting barfrom terminals E, F and G, connectingE and F together, and connecting theretroactor coil terminals C and D to Fand G. The coil is now in series withthe grid winding of the last high -frequency transformer. In the case ofshort waves, retroaction is usually ob-tainable by adjusting the potentiometer.

Fig. 13 shows Type 55B. The useof a condenser between the transformerwindings has now been abandoned,chiefly because capacity effects lessen theefficiency of high -frequency amplifiers,especially when short waves are beingreceived. Type 55B is intended to re-ceive waves having a length of from100-130 metres. Capacitative retroac-

672

CONSTRUCTION OF VALVE AMPLIFIERS.

tion is obtained by means of a small cop-per plate inserted between the anodeclip of the second valve and the gridclip of the third valve. This plate isconnected to the first grid and is suitablyinsulated.

A special feature is the use of an ebon-

be gradually loosened, the operator re-tuning, as may be necessary. Thegrids of the amplifying vacuum tubeshave their potential varied by the poten-tiometer P. Cumulative rectification isused, although the leaky condensercan be dispensed with and rectification

00

p(Th

LC><

OL2Q1°

at445 7.?

2OO

;TN /16 e7

(:).*C) 117,?__J co R

606 -0--1-;*--

pu0) 2_01_

717,-avr`-r-B;

Fig. 14.

ite rod in which are mounted iron -coresof a peculiar type consisting of cylindersof paraffin wax impregnated with finely -divided iron. By sliding the cores inor out of the transformers close tuningmay be accomplished. It would appearthat on later amplifiers these special coresare omitted.

A type of high selectivity used by theauthor during some experiments is

shown in Fig. 14. It will be seen thatthe intermediary transformers are of theloosely -coupled type which eliminateinterference to a very marked degree.Consequently, the circuit is really onlysuitable for reception on a given wave-length, owing to the difficulty of rapidtuning. The circuits should first betightly coupled and tuned to give thebest results. The coupling should then

obtained by taking advantage of thenon-linear characteristics of the grid oranode current curve. Retroactive am-plification may be obtained by couplingthe retroactor coil L to a suitable pre-ceding inductance. " A modification ofthis circuit consists in making the anodecircuits aperiodic and the grid circuitstuned.

(To be continued.)

CORRECTIONS.

In our report of Mr. Scott-Taggart's Paperon a " Syst m for the Reception of ContinuousWaves " (January issue), the word " unless "in the second column of page 597 should read" when." In Fig. 1 (page 594), the transformerT1 T2 should be shown as a step-uptransformer, while in Fig. 3 (page 600) thetransformers T,, T4 and T, T2 should be of thestep-down type.

67;.-1

The Construction of AmateurWireless Apparatus

This series of articles, the first of which was published in our Aprilnumber, was originally designed to give practical instruction in the manu-facture o/ amateur installations and apparatus, and arrangements had beenmade with Marconi's Wireless Telegraph Co., Ltd., to supply completeapparatus to the designs it was intended to detail. The restrictions

on amateur work, however, remained in force, and the author was com-pelled to proceed on general lines only. A further series will be pub-lished giving the class of information originally intended.

Article Eleven. --HIGH-TENSION SUPPLY (continued).

THE arrangement shown inFig. i of our last articlecan be still further simpli-fied by the choice of a

valve of suitable design.The working voltage of any practicaldesign of valve is mainly governed bythe mesh of the grid. The reader willunderstand that by " mesh " we meanthe spacing of the wires forming thegrid; the latter may, of course, notactually be a mesh in the ordinarysense of the word, but may consist ofa spiral of wire enclosing the filament.In general, the more open the mesh ofthe grid the lower the working voltageof the valve. This fact may beutilised in the design of a very simpleheterodyne receiver. By opening themesh sufficiently a valve can be pro-duced which will oscillate satisfactorilywith a pressure of only two or threevolts applied to the plate. An exampleof such a valve is the " V24 " patternmanufactured by the Marconi Company.In Fig. 1 we illustrate a separate oscil-lator working on this principle.

In this Fig. A represents the usualoscillatory circuit consisting of aninductance shunted by a variable con-denser, the proportions of the circuit

being suitably adjusted for the wave-length it is desired to receive. Thiscircuit should have a fairly large L/Cratio. A safe value to take for themaximum capacity of the condenser isopoi mfd. Of course a smaller con-denser will be quite all right, but thecapacity should never exceed the before -mentioned value or difficulty will beexperienced in making the set oscillate.Assuming that the voltage across thefilament of the valve, when burning atthe correct brilliancy, is about fourvolts, the accumulator should have anE.M.F. of six or eight volts, the seriesresistance R being used to adjust thefilament current to its correct value.C is the reaction coil connected in the

674

Fig.

CONSTRUCTION OF AMATEUR WIRELESS.grid circuit of the valve; it operates inexactly the same manner as described inprevious articles.

Referring to the diagram it will benoticed that we have connected theseries resistance in the positive leadfrom the battery and that the plateoscillatory circuit is connected directlyto the positive terminal of the batteryitself. It is therefore clear that theplate will be at a potential of six oreight volts positive to the negative legof the filament, depending on thevoltage of the battery employed forlighting the filament. This voltageis quite sufficient to cause the valveto maintain continuous oscillationsin the circuit A when the reaction coilis suitably adjusted. The oscillationsproduced will not be of large amplitude,but will be quite strong enough to giveinterference tones with continuouswave signals when the circuit is coupledmagnetically with any spark receiver.As a matter of fact a weak heterodyneis an advantage for receiving work. Ifthe local oscillations are too strong thedetector may become saturated, withthe result that signals will be weakenedand may disappear altogether. Alsothere is less likelihood of interferencewith other stations owing to the in-duction of appreciable currents in thereceiving aerial (we shall return to thispoint later).

The same principle can be equallywell applied to a self -heterodyne valvecircuit. Such an arrangement is illus-trated in Fig. 2. This circuit will beseen to be similar to the coupled con-tinuous wave receiver described in aprevious article, with the exceptionthat the high voltage battery has nowdisappeared. It will be observed thatwe have shown the telephone trans-former shunted by a condenser. Thiscondenser is very important. It pro-vides an easy path for the high fre-

1/

Fig. 2.

quency oscillations past the telephonetransformer. Owing to the high im-.pedance of the high resistance windingof this transformer, it is very difficultto make the circuit oscillate unless thewinding is shunted by this condenser.A suitable value is about .003 mfd.This small capacity will not act asa shunt to the low frequency rectifiedbeat current, and consequently thestrength of signals will not be affectedby its presence.

Should any difficulty be experiencedin getting either of the above simplecircuits to oscillate the postive potentialapplied to the plate should be increaseda little. This can be easily done byconnecting a four -volt flash lamp bat-tery in series with the plate winding.This battery should be connected atthe bottom end of the winding,i.e., the negative end of the flash lampbattery should go straight to the positiveend of the filament lighting battery.Difficulty will also occur if the insu-lation of the condenser is not good .n

675


the coils are damp. It is preferable, ifpossible, to use an air condenser; andthe coils should be wound on highlyinsulating formers, thoroughly dried outand then given a coat of shellac varnish.

We have referred to the question ofinterference caused to other stations bya continuous wave heterodyne receiver.This question is very important and wepropose to make a few remarks on thesubject.

The cause of the trouble will beperfectly clear by a reference to Fig. 5of Article Eight (November 1919 issue).This Fig. illustrates a direct coupledself -heterodyne receiver, the aerial beingdirectly connected to the grid oscillatorycircuit. Now it is perfectly clear that,when the valve is oscillating, anundamped oscillatory current will flowin the aerial during the whole time thatreception is taking place. The aerialwill therefore be radiating a continuouswave whose wavelength correspondsto the tune of the receiving circuit.This wave will be very weak, becausethe currents flowing in the receivingcircuit are very small; but the sensi-tivity of a heterodyne receiver is sogreat that it may be clearly audible atanother station several miles distant,and may cause interference if thesecond station happens to be receivinga weak signal. Also as the receivercondenser is turned round annoying" swoops " will be heard at the seco'idstation. It may be that regulations willbe introduced forbidding the use of

direct coupled self -heterodyne circuitsfor continuous wave reception.

The trouble can be minimised bythe use of the coupled circuit receivershown in Fig. 6 of Article Eight. Whenusing this arrangement the aerial istuned to the wavelength of the incomiogsignal, whereas the grid circuit is tun..11to a slightly longer or shorter wave inorder to get a beat note. And sincethe coupling between the aerial coiland the grid coil will be very weak, onaccount of this mistuning only a verysmall current will be induced in theaerial itself. Or at any rate, the cur-rent in the aerial will be very muchsmaller than that in the grid circuit ofthe valve. Consequently the intensityof the radiated wave will be very muchless in this case than in that of thedirect coupled circuit. The chieftrouble experienced with this inductivelycoupled arrangement is the difficulty of" finding " any station. Owing to theextreme sharpness of tuning of tiv:circuits the condensers have to be veryaccurately adjusted to get the signals.This is, however, a matter of practice,and the amateur will soon get expertin the manipulation of the circuit whenonce he has grown accustomed to thecircuit. It is very useful when firstsetting up the receiver to make out atable of condenser adjustments foundfor different stations. This table canhe placed in a convenient position andreferred to when it is desired to pick upany station.

AMATEURS !Do you want to know how to design and make

FRAME AERIALS WAVEMETERSTELEPHONE TRANSFORMERS

WIRELESS TELEPHONESIf so, watch the future issues of The WIRELESS WORLD.

676

1

Questions and Answers --a:-

;--1-1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111-117

NOTE.-This section of the magazine isplaced at the disposal of all readers who wishto receive advice and information on matterspertaining to both the technical and non-technical sides of wireless telegraphy. Readersshould comply with the following rules(I) Questions should be numbered and writtenon one side of the paper only, and should notexceed four in number. (2) Queries shouldbe clear and concise. (3) Before sending intheir questions readers are advised to searchrecent numbers to see whether the samequeries have not been dealt with before.(4) The Editor cannot undertake to reply toqueries by post. (5) All queries must beaccompanied by the full name and address ofthe sender, which is for reference, not for pub-lication. Queries will be answered underthe initials and town of the correspondent, orif so desired, under a " nom -de -plume."(6) Readers desirous of knowing the con-ditions of service, etc., for wireless operatorswill save time by writing direct to thevarious firms employing operators.

A. E. P. (Manchester) (r): The reactance ofa condenser is defined as the negative quantity-4241K. The Hawkhead and Dowsettformula z2rnL- 1/22rnK which is equivalentto 22rnL4-( -tizirnK), is therefore the sum ofthe reactance of the inductance and the nega-tive quantity which is the reactance of thecapacity. (2) The units in the above formulaare Henries and Farads.

S. J. (Solihull) (1).-The capacity of thecylindrical condenser you mention will beabout 43 micro- microfarads. (z) A coating ofvarnish will theoretically slightly increase thecapacity, but unless the coating is very thickthe increase will be quite negligible.

T.H. (Liverpool) W.-When an ionic tube isused with a condenser in the grid circuit, theunidirectional current flowing in the grid cir-cuit tends to charge this condenser. If thischarge is allowed to build up, the resultantpotential across the condenser alters the po-tential which the grid initially has, and whichcorresponds to a sensitive point on the gridpotential -plate current curve, to a new valuewhich corresponds to a flat and therefore in-sensitive part of this curve. The tube there-fore loses its sensitivity very quickly unlesssome means of preventing this potential frombuilding up in the condenser is supplied. Themost convenient way of doing this is to put aresistance across the condenser by which thecharge may slowly leak away as it accumu-lates.

WABTEE (H. M. T. Aro.) (t).-We thinkthe performance you record probably does ap-proach a record for short power range, al-though we cannot, of course, say for certain.With amplifying receivers freedom from jam-ming at the receiving end is one of .he 'nos(important factors in working long distances,and you were probably exceptionally favouredin this respect. (z) Excluding the watts lostin your i6 c.p. lamp, we do not think thatyour primary power can have approached asmuch as 5o watts,-it was probably nearer20. Your effective aerial watts would nothave been more than to at most. (3) Thisconnection probably introduces a self -capacityoti its side of the buzzer break. This tends tocharge up at the instant of break, thus help-ing to prevent the stored energy of the cir-cuit from discharging as a bad spark acrossthe gap. (4) Dispense with the condenser,and use a telephone transformer. Tie circuitwould tune so very flat that it is not woi thwhile attempting it.

H.V.G. (S. S. Sheafdart).-The station doesuse a C.W. arc for most of its traffic. Thetearing tone at short distances is common,and is due to variations in arc discharge.The higher pitched note is not so common.As you apparently only hear it at short dis-tances from the connections you mention itmay be due to forced oscillations in the re-ceiver setting up beats with the incomingradiation. As you do not say whether thepitch varied with the tuning, we, cannot sayfor certain, and this may also have been dueto irregularities at the transmitting station.

SPARKS (Plymouth) (t).-zzo volts A.C. isquite unsuitable for grid potential of a valve,even with a lamp of any size in series. (2) Thedesign of a wireless telephone set for a givenrange and a given aerial is rather outside thescone of these columns. The loop aerial yousuggest is quite unsuitable. If you must usea loop, use a former several feet in diameter.The T aerial would be fairly suitable. Fordetails of suitable circuits see Goldsmith'sRadio Telephony, or Bucher's Vacuum Tubes.

A. E. B. (Welling) (s).-The aerial wouldbe suitable for short wave stations at not toogreat distances. It would be very little usefor large stations on long waves without com-plicated and expensive apparatus, and a greatdeal of skill in manipulation. (2) No 24wire would be quite suitable for the induct-ance, but you would probably not want asmuch as you suggest for the wavelengths forwhich your aerial would be suitable. (3) Thesketch you give is fairly suitable for an ele-mentary receiver. (4) Ordinary phones are

677

- 0


suitable for wireless work if they are of suit-able resistance,-i.e., about the same as thedetector in use. Most crystals have high -resistance and therefore need high -resistancephones. Unfortunately most ordinary phonesare low resistance. (You should consult abook such as Bangay's "Elementary Prin-ciples," in which you will find the answers -o!nos, difficulties such as these which botherbeginners.)

GADGET (Bournemouth).-The conditionfor the oscillatory discharge of a condenseris arrived at mathematically, roughly, as fol-lows. The differential equation for the varia-tion of the charge can be written down fromfirst principles, and is :-

d2q R dqdta L dt + LC

Solving this by methods given in any ludicon differential equations, we get

Rq = Ae (- 2L IN/4L° - 17,C)

R2 I \

Now this is the equation to an oscillatoryquantity if, and only if, the expression in thebracket is imaginary ; and from fairly elemen-tary algebra, this is the case if

R24L2 LC is negative, i.e., if-

2 <R L or, if R V4-74 which is the

required condition.M. D. M. (Cricklewood) (1).-An inductive

reaction coupling, though very convenient inpractice, is not essential for producing oscil-lations. Oscillations can be sustained by anymeans by which the change of the plate cur-rent can be made to affecc the poten-tial of the grids provided that thesense in which the potential is changedis such as to assist the changes inthe plate current and not to damp them out.Thus in your first example the grid potentialwill vary with the charge on the A.T. conden-ser, which in turn will vary with the platecurrent. The circuit will therefore be capableof oscillating. Lt can then be tuned for thelocal oscillations to beat with the oscillationsinduced by the incoming waves. Your circuit2 probably oscillates owing to the connectionbetweetz the plate and the grid circuit conden-ser when the ultra-audion switch is closed.We do not think it likely that it would oscil-late with this connection broken, ac any ratewith hard valves. (2) We believe so. (3) Thisarticle duly appeared in the WIRELESS WORLD,Vol. V., p. 280. (4) The scheme for chargingcells from a vacuum tube rectifier is practic-able, if a suitable valve is used, as for instancethe Tungar bulb of the B.T.H. An ordin-ary valve as used in receiving circuits wouldnot pass enough current.

J.S.F. (Herne Hill).-We do not, think thescheme of connections you suggest would givegood results, and it differs so much from usual

practice that we could not give the best valuesfor the inductances and capacities-particularlyas you do not give the dimensions of -the aerialyou propose to use, or the wavelengths youwish to receive. We recommend you to tryone of the more usual circuits to begin with.

NEMO (Aberdeen) (z).-Auto transformerswould not be suitable, as their use would putcomparatively low -resistance paths between thepositive end of the H.T. battery and the fila-ments. (2) The exact value for the condenseris not important-try 0.25 mfds., variable in afew large steps. The circuit could be adaptedfor note magnification by substituting an ironcore transformer for the second H.F. trans-former shown. A telephone transformer wouldalso be necessary in the plate circuit of thethird valve with low resistance phones.

J. W. (S. S. Mahsud) (t).-In view of thevery high resistance of the grid leaks, we donot think that the introduction of a battery inthe manner you suggest would be of any use.It would certainly not increase the ease of con-trol. (2) About to,000 to 20,000 ohms. Suchcrystals can be used as grid condenser leaks,but would not have high enough resistance forthe circuits in the diagram you mention. (3)The circuits of the amplifier are quite differ-ent, (vide Fleming's new book). The ampli-fier should, of course, be used with suitablereceiving circuits, and is then quite reliable.

TRAMP (Birmingham (t). --The poles youdescribe would serve very well for masts foran aerial. Sink them in concrete sockets t, adepth of about 3 feet below the level of theground, tar or otherwise protect the earthedends, and stay the poles securely from about35 feet up. Use four stays with their anchorsat the corners of a square with 25ft. sides.(2) We can give you no idea of the cost of theapparatus you mention and advise you to applydirect to the makers.

G. W. (Preston).-Your question is so verycomprehensive that it is difficult to answerbriefly. We think, however, that you wouldhave little difficulty in obtaining a position asa sea -going operator. Posts ashore are not soeasily secured, as there are fewer available.It will save time if you write direct to thewireless companies.

PATENTS, Inventions, Trade Marks.-Advice and handbookfree.-King's Patent Agency, Ltd., r65, Queen Victoria

Street, London, E.C4,

'TECHNICAL BOOKS. Second-hand and New Books on everyconceivable subject. Catalogue free. State wants. Books

sent on approval. Books bought.-FOYLE, 121/125, CharingCross Road, London.

LEARN DUTTON'S 24 -HOUR SHORTHAND ; booklet free.-DUTTON'S COLLEGE, Desk D15o, Skegness.

WIRELESS WORLD. Nos. I to 77 inclusive, spotless.Best offer over Ca. -6o, Becher Street, Derby.

678

THE WIRELESS WORLD ( I dvertisemenrs

11;.

DU ILIkcofiDE*5Eiu

rorVire1eSs Transmitting C5-PeceiN)in

CONDENSERS FOR ALL PURPOSES

DUBILIER CONDENSER CO. LTDDucon Works,

Gold hawk Road Shepherds Bush- LONDON -W.12Telephone -Hammersmith 1084,Telegrams-Illivoltcon Phone, London.Code - Marconi International.

ALL AMER/CAN ENQU/NES TO BE ADDRESSED

Dubilier Condenser Co.Inc. 217 Centre Street, New York.

February, 1920. xi Please mention the Wireless 'TVorld

T E 117 RE LESS W 0 RLD (Advertisements)

CanYouDrawthisDawsonGirl

GOLDEN AGE tor. ARTISTSHOW CHAS. E. DAWSON HELPS BEGINNERS.

THIS YEAR the demand for simple, effectivesketches will break all records.Advertisers now pay daily thousands of poundsto men and women whom, by post, Chas. E.

Dawson has taught to draw for reproduction.Beginners who had never earned money by

Art work at home are making good incomesin this new, profitable, and interestingprofession.Chas. E. Dawson 'Creator elite'. Dawson Girl"and Founder of ngland's FIRST and GreatestCorrespondence Art College) does not teach so.called comic drawings, but well -paid designs forPosters. Covers, and dignified Advts., that appeal

to people of refinement. He is prepares to sendcriricn.m. advice, and particulars of present

openings for beginners to any read, r whosends Girl's Head sketch. with stamp for

return, to him at the Practical Corres-pondence College. Ltd., 69. Thanet

!louse, Strand.It is easier to help those

whose sketches show unusualpromise, and for them a

few Scholarships arereserved, at reduced

fees, payable insmall instal-

ments.

Accessible to YOU on Palmers:No. e-DryItry Abbey.famoSis for its associations wan

Sir Walter Scott.

Spin out the leagues between you andhere on the wonderful friction -free Palmers- whichbecause of their Palmer Fabric Foundation of rubber -insulated strands give greater resilience, more mileage, lesspunctures, and transmit more energy from pedal to road.Write now for FREE Palmer Map Book (D. 12)Sectional Maps of British Isles. smith Roads, Distances, and

Tip.. Send a P.C. at once to make sure of a copy.THE PALMER TYRE Ltd., rto-so3, Shaftesbury Avenue.W.C.o. Cycle Tyre and Repair Depot. to3, St. John Street.

Clerkermell,

CYCLE TYRES_And MOTOR CYCLE TYRES

DAVIS & TIMMINS,LIMITED,

KING'S CROSS,LONDON, N.

TRADE

Established 1876.

MARK

METAL THREAD SCREWS.

Nuts, Bolts, Terminals, &c.

Telephone North 580 (2 lines:.Telegrams: '' Conductivity, London."

February, 1920. Please mention the Wireless World


Pelmanists v. Non Pelmanists." HAVE altered a good deal under the grip-

ping influence of your Course, and continueto do so-I have gained tremendously on thespiritual or intellectual side-and, as far asmoney is concerned, I am now possessed of

a life-long (I am sure it will be life-long) impetuswhich will make it impossible for me ever to needmoney. I have earned and gained more cashsince I took the Course than during any previousperiod of the same time.

" We most of us have competitors and rivals-and woe to the non-Pelmanist who tries to runthe race and win against a Pelmanist." (F13I3I.)

The above letter has recently been receivedby the Pelman Institute. Some may consider ita remarkable letter. It is not a remarkableletter, however, from the Pelman point of view,as hundreds of equally striking letters are re-ceived by the Institute almost every day. Butit contains certain points which will interestevery reader.

MAKING BRIGHT MINDS.In the first place, it emphasizes the intellectual

benefits of Pelmanism. " I have gained tremen-dously on the spiritual or intellectual side," saysthe writer. The practical, business, and financialbenefits which follow from a course of Pelmanismare so striking that sometimes this particularfeature of the Pelman Course is apt to be over-shadowed. But it is always present all the same.The atmosphere of optimism, the bright keennessof spirit, developed by Pelmanism is testified toby thousands. Men and women of all ages andprofessions write continually to say how Pelman-ism has benefited them intellectually, how it hasgiven them a new outlook on life, how it hasopened to them rich stores of knowledge andenjoyment unknown to them before, how it hasrolled away the clouds of depression and unrestfrom their minds and enabled them to live fuller,richer, and happier lives. The records of thePelman Institute are full of such cases. Thegood that Pelmanism is doing in this directioncan never be over -estimated or too highly praised.

INCOMES QUADRUPLED.But then turning to the more practical side of

Pelmanism, " I am now possessed of a life-longimpetus" says the writer, " which will make itimpossible for me ever to need money. Ihave earned and gained more cash since Itook the Course than during any previousperiod of the same time." This same experi-ence has been that of thousands. Space isinadequate to give the slightest idea of the workPelmanism doin in

doubling, trebling, and quadruplingthe income -earning power

of those who take the Course. In every pro-fession that could be mentioned, in every formof business or industrial work in which people

are engaged, there are literally hundreds of menand women who are earning bigger money, hold-ing higher positions, and rising rapidly to thesummit of their ambitions entirely through theincreased efficiency brought about by a shortcourse of Pelmanism.

165 PELMANISTS IN THE FIRM.So greatly is the value of Pelmanism appreciated

by business men that batches of enrolment formsare constantly applied for by business firms inorder that the whole of their staffs may beenrolled simultaneously. Well-known firms haveenrolled as many as

165, 145, 100, and 70members of their staffs in this way

at one time.A well-known business man writes :-"I do not see how anyone can study the

Pelman lessons seriously and not gain thereby,reaping a reward which-besides its definite and,in my case, tangible advantage-also brings withit developmentswhich have no parallel in moneyvalues.

" To those of my acquaintances who have beensufficiently interested to ask my opinion of thePelman training, I have said-and shall continueto say :-

" ' Take it-follow instructions carefully-andif at the end of the Course you do not admithaving gained something good, right out of pro-portion to its cost, I will personally refund youroutlay.' "

TO -DAY'S GREAT OPPORTUNITY.No one who wishes to get on-and who does

not ?-can afford to do without Pelmanism. Ifyou are efficient already, Pelmanism will makeyou more efficient still. If you are handicappedby faults which keep you down-mental faultssuch as indecision, forgetfulness, pessimism,timidity, lethargy, and so on-Pelmanism willbanish these faults and make you alert, resource-ful, keen, and efficient.

Yet Pelmanism takes up little time. Its costis small,and it is perfectly easy to practise. Nohard study is Pelmanism, but a pleasant, delight-ful, and exhilarating recreation for your mind.Learn all about it to -day. A postcard or letterwill bring you full particulars post free by return.A copy of " Mind and Memory," a copy ofTruth's Report on Pelmanism, and particularsenabling you to enrol for the complete Courseon special terms will be posted you directlyyour application is received. Or call personallyif you can. Address the Pelman Institute,145, Pelman House, Bloomsbury Street, London,W.C. 1. You will never regret it.

February, 192o. xiii Please mention the Wireless World


Wew edition in T'Tho Volumes

Text -Book on Wireless TelegraphyBy RUPERT STANLEY, B.A., Tp. Maj., R.E., and Chief Wireless Instructor in the B.E.F., France

8uo. With Illustradons

Volume I. General Theory and Practice. 15s. net.Volume II.-Valves and Valve Apparatus. I 5s. net.

" Some of the results of the rapid developments of the hard vacuum valve, and of valve circuits, are dealtwith in the second volume, which is the most up-to-date book on the subject published. Major Stanley'sfirst volume has been recognised as a standard work.--Vhe Scotsman.LONGMANS, GREEN & CO., 39, PATERNOSTER ROW, LONDON, E.C. 4.

THE NORTH WALES

Wireless SchoolsCARNAR VON

The Home of WirelessSchools ideally situated. Pupilsaccepted for board -residence.

Special Postal Course for Amateurs.Write for Free Book "Selecting a Career."

CONDENSER

PLATESAICAVIICANITE SUPPLIES

LI MITE!).(IA ICA MOUSE ,OFFORD ST

LONDON, N.I.PRone porta-% 805.

VARIABLECONDENSERS

These condensers are moving vane typefitted in lacquered brass case and engravedin degrees from 0 to 90. They are continu-ously variable with an even scale and madein the following maximum capacities :

0.00050.00100.00150.00200.0025

m.f. £2 15s.£2 17s.£3 Os.

£3 2s.£3 5s.

Od,6d.Od.6d.Od.

Calibration Chart in direct readings ... 2/6 extraWith divided scale engraved in micro-microfarads 5/- extra

The MARCONI SCIENTIFIC INSTRUMENT E?-i5

21-25, ST. ANNE'S COURT, DEAN ST., SOHO, LONDON, W.1Telephone : 7745 Gerrard. Telegrams : THEMASINCO OX LONDON

February, 192o. xiv Please mention the Wireless World


The Big CIGARETTE with the Choice FlavourSILK CUT VIRGINIA

xv

20brr /--r10064A 50A -Y2

d01 High Class Tobacconistsan Stores everywhereManufactured byMAJOR DRAPKIN Cb" O I-- O C=.KingdomTODheC OhOt Lo

P.0



ACCUMULATORSFOR WIRELESS & EXPERIMENTAL WORK

ELECTRICALeSTORAGE Cf

LIMITED

CLIFTON JUNCTIONMANCHESTER

LONDON OFFICES -39 VICTORIA ST., S.W.1

1837 1919

"

A1-.3 'ESgive to the userthe fullest satis-faction and tothe contractorthe greatestcredit - always

W. T. HENLEY'STELEGRAPH WORMS CO., Ltd..

Blomfield Street, LONDON, E.C.2

February, 192o.

BRITISH & FOREIGNSAILORS SOCIETYEstablished 1818 Incorporated 1905

For over a Century this Society has worked" IN SERVICE FOR THE SAILOR "SAILORS' RESTS are established in many

PORTS THROUGHOUT the WORLDSea Training for Boys.A Nautical School for Young Sailors.A Large Relief Department for Sailors and

Dependents.The International Sailors Brotherhood.Memorial Hostel for the Port of Loudon.

WILL YOU HELP US ?Donations gratefully received by Sir Frederick GreenK.B.E., Honorary Treasurer, 32 Cheapside. London, E.C.2

Bankers:

BANKOFENGLAND

GeneralSecretaryRev. T.EYNONDAVIES

POSH SLACKSPERFECT CREASE-LONGER WEAR

- Bought by Thousands of officers.I , A Necessity for Camp or Civil Life.

`ALPHA' PORTABLEHandiest Trouser Pressever madeWeighs vo ozs. Parks into 2I in. by2 in.by 3 in. Hangs in Wardrobe whenin use.No. 1 post freeNo. 2 Press and Suit

-ingitHanger combined. 8/6Post Free U.K.(France 6d. Extra.)

Cros Cheque or P.O. LondonCiry and Midland Book."

7/ -

MAY & CO. 3, TUDOR STREET,° LONDON, E.C. 4

ALL ENQUIRIESrespecting Advertisementsin the "Wireless World"should be addressed

To the

ADVERTISEMENT OFFICES,BERTRAM DAY & CO. LTD.110--111, STRAND, LONDON, W.C.2

Telephone- 8166 Gerrard.

xvi Please mention the Wireless World

THE WIRELESS TI'ORLD (Advertisements)

WIRELESSMARCONIINSTALLATIONS

TELEGRAPH

Enquiries invited for WirelessTelegraphInstallations for communication overany distance, in any part of the WorldPORTABLE APPARATUSFOR ARMY PURPOSESIn addition to Installations, Special Apparatus has been

designed for many purposes, amongst others :-AP PA RATUS FOR ACTUATING FOGSIGNALS BY WIRELESS TELEGRAPHY

SELF - CONTAINED RECEIVERS FORTHE RECEPTION OF TIME SIGNALSWIRELESS COMPASSES TO ASSIST

NAVIGATIONPRACTICE BUZZERS FOR INSTRUCTIONIN TELEPHONE MORSE SIGNALLING

PORTABLE WAVEMETERS,DECREMETERS, INDUCTION COILS,

etc., etc.

Marconi's Wireless Telegraph Company, Limited,MARCONI HOUSE, STRAND, LONDON, W.C.2.

Telephone . t710 CITY. Telegram EXPANSE, ESTRAND, LONDON

February, 1920. xvii Please mention the 'Wireless !For d


Alternating and Direct CurrentGENERATORS and MOTORS

D.C. MOTOR -DRIVENAIR COMPRESSOR.

GENERATORS SELF CONTAINEDOIL AND STEAM GENERATINGPLANTS FOR WIRELESS AND SHIPLIGHTING BATTERY CHARGING, @c.

Also aCanufacturers of : :

HIGH FREQUENCY MACHINESBOOSTERS SWITCHGEAR ARC LAMPSCONVERTERS INSTRUMENTS PROJECTORS

CIZOMPTON & CO. LTD.TelegramsCrompton. Chelmsford CHELMSFORD

Telephones :-161 Chelmsford(3 lines)

McGRUER SPARSThe ACME of STRENGTH

and LIGHTNESS.This Hollow Wooden Structure is ideal forWIRELESS MASTS (telescopic or in onelength), AERIAL SPREADERS, IN-DUCTANCE FORMERS, etc.Combination Flag Pole and Mast in three sectionsextending to 25 feet, weight 9 lbs., completewith guys, halyards and pickets : Price £6 6s.The efficiency of these Spars has been proved bytheir use in Aircraft Construction. The fuselagesof the VICKERS VIMY ROLLS which flewthe Atlantic and from England to Australia, areconstructed with McGruer Longerons and Struts.The successful HANDLEY PAGE V.1 Soo hasMcGruer Spars in the fuselage, wings, and tail unit

These facts speak for themselves.

WRITE FOR BOOKLET.

ALL INQUIRIES WILL RECEIVEPROMPT ATTENTION.

COMMERCIAL ROAD,LAMBETH, LONDON, S.E.1

Telephone : Hop 718.Teleg. : "011osparsh, Warloo, London.

February, 192u. Please mention the i reit' ss World


ATLANTICCOLLEGE

OF

Wireless and SubmarineTelegraphy, Cahirciveen.

Send your boy to the centre ofthe Telegraphic World to learnWireless or Submarine Telegraphy.

Most Successful Tuitionby fully qualified Staff.

Students can qualify for shoreappointments, as the College isequipped with the most completeand up-to-date Wireless Plant inIreland - an exact facsimile ofShore and Ship installations.

Illustrated Prospectus on application to

M. M. FITZGERALD, A.M.I.E.E.Principal.

ESTABLISHED 1809.

NORTH BRITISH& MERCANTILEINSURANCE COMPANY

FIRE LIFEACCIDENT ANNUITIESBURGLARY MARINE

FUNDS

£24,650,000Chief Offices :

LONDON : 61, Threadneedle Street, E.C. 2.EDINBURGH : 64, Princes Street.

" You cannot charge me with not preparing betimes to assistyou to secure your due share of World Trade after the War."

-J. C. H. Macbeth.

HAVE YOU HEARD ABOUT THE WONDERFUL

Marconi InternationalCODE ?

THE CODE THAT IS MORE THAN A CODE.It halves the cost of Cabling, and is an Interpreting Agent and via

Phraseological Dictionary in Nine Languages. It places in rc0%9,your hands the Master Key to the Trade of the Globe I. \t.

0,"

We shall be pleased to send you, free of charge, our Linguistic Map of the Worldand Handsome Illustrated Booklet if you will cut off this corner, pin it to one

of your letter headings and post it to us. ;,/.z), 4,9'0,4. 0"

04> ,4>4\Vet5/0,N:l'THE MARCONI INTERNATIONAL CODE CO., LTD.

Marconi House, STRAND, LONDON.

February, 192o. xis Please mention the Wireless World

THE WIRELESS WORLD (Advertisements),

WIRELESS ENTHUSIASTSWE have now ready our Receiving Set No. 140, for C.W. Reception. This Set is

quite unique and will give you extraordinary results. Price £6 6s. Od.Complete including Valve.

Our Set W.R. 139, for Spark and C.W. Reception, with a Wave Length from 400 to 20,000metres. Price £18 18s. Od. The demand has been so great for these Machinesthat orders are being dealt with strictly in rotation. We are the actual Designersand Manufacturers of these Sets. Prov. Patent No. 347/20

WE HAVE ALSO IN STOCK :-Valve Amplifiers. Telephone Transformers from 35/ -Grid Condensers 8/6 Intervalve Transformers £3 3s.Grid Condensers with Leak 12/6 AERIAL WIRETuning Coils from £4 Variable Condensers 35/ -Valve Holders 12/6 Potentiometers 18/6Selected Crystals Loading Coils from 30/ -

We also have a splendid stock of Valves specially designed for Amateur use, workingfrom z volts at 22/- to 35/.. These are not WAR STOCK.We have a Staff of Experts at the disposal of our customers to advise and help inerecting and choosing suitable Apparatus to get the best results on the Aerial permittedby the P.M.G. of the G.P.O.

F. 0. READ & CO., LTD., Wireless Experts,Telephone : Gerrard 442. 13-14, GREAT QUEEN STREET, KINGSWAY, W.C.2

Li11111111111111111111111111111111111111111111111111111E1111111111111111111111111111111111111!--:

CONQUEST= THE NEW=== ILLUSTRATED MAGAZINE== OF POPULAR SCIENCE=

Read itEachMonth

1Monthly

CONQUEST records, describes, and explains all thegreat achievements of modern Science, Invention,and Industry. It takes its readers " behind thescenes " and shows them " how it is done."

CONTENTS FOR FEBRUARYThe New Heresy of Man's Descent.How a Gramophone Record is Made.The Story of GlassThe World of Sound.

'= Germanys Commercial Airships. .- -- -.... Flame. Comet Terrors. &c. &c. &c.= -

Subscription Rate i 5s. per annum, post free.

Monthly,=-- Published 12-13, Henrietta Street, London, W.C. 2. --T111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111117

February, Ipso. xx Please mention the Wireless World

The Unitwhich every

wirelessexperimenter

is talkingabout.

Sketch of


RECEIVING ANDAMPLIFYING VALVES.

Thermionic Reception Valves.-Best British manufacture, guaranteedtested before despatch. Filamentcurrent. 4 volts, 0 '8 4 amp., witha working anode potential of 50/70 volts,each 25/, Cheaper pattern 22/6.

Post and Registration 1/3.

"PESCO''FIXED CONDENSER.

For crystal or valve circuits. Ebon-ite insulation throughout casing oflacquered brass, Real instrumentfinish. Each 8/-. Cheaper patterns

from 3/11

WIRELESS APPARATUS.As in the good old days we have everything necessary for theAmateur or Professional Experimenter, all material for Valve Systemsbeing in stock. Permits must accompany all orders for this Dept.

Wireless List mailed for 3d.VALVE PANELS.-Of that fine instrument which appeals to the professionalexperimenter. Insulation ofsolid ebonite given a dull mattfinish, woodwork of solidmahogany piano finish. Theconstruction of valve holdersensures perfect rigidity. Allleaders are soldered toterminals, which are clearlyengraved.

FINESTINSTRUMENTFINISH.

". s1 1 1

""IIPii1 1.1111 IIp1111011011111111

No. I-For I Valve .. each 22'6 No. 2-For 2 Valves ... each 421 -No. la-Ditto. with Filament No. 3 --For 3 Valves ... 60/ -

resistance ... each 39/- Valves extra. according to selection.ANY OTHER PATTERN BUILT PROMPTLY TO ORDER.

SOME OF OUR OTHER WIRE-LESS COMPONENTS, TuningCoils, Grid Leaks, High Value Resist-- ances for valve couplings, " Brown" and

Pesco ' Headgear, Loading Coils,Insulators Aerial Wires, Etc.. Etc.

INSPECTION INVITED.

"PESCO"VARIABLE CONDENSER.

Suitable forcrystal orvalve circuits.moving vanetype withpointer andscale asillustrated.Mountedin solid:mahogany! -case. Eboniteinsulation.

Each 30,' -

KNIFE SWITCHES on EBONITENew Pattern special for WirelessWork,positive contacts. Instrument finish.

Single Throw Patterns.Single Pole . each 2/11 post 2d.Double Pole ... 4/11 4d.

Change Over Pattern.Single Pole ... each 3/11 post 3d.Double Pole ... 5/6 4d.Tripole Pole Patterns ready shortly.

VALVE DETECTORS.nBeing a completeUnit, for adapting

::,,,,,,,A your pre-war outfit.014 1 Necessary con-

densers and leaksbeing fitted, the fol-lowing componentsare needed to makea complete station,

viz : - Tuner,'Phones, H.T.Battery, Fila-

mentBattery,Variable

C on -denser

connections for G.P.O. Requirementssupplied with all orders.

No, I-Without Filament Resistance ... each,67'6No. 2-Fitted with Resistance as illustrated, each 85'.MITCHELLS 158. RYE LANE.

PECKHAM, S.E.15

HIGH TENSION BATTERIES.AS SUPPLIED TOTHE ROYAL AIRFORCE

PESCO

60 VOLTS

NO R 4.4?

60 Volt Unit as illustrated, with leads lions each 15 Volt Group forattaching selecting switch or plug panel. each 2216. Each one thoroughlytested and guaranteed to be Best British Manufacture as supplied tothe R.A.F. No. 2-100 Volt Unit, positive and negative leads only.each 32/6. SPECIAL BATTERIES BUILT UP PROMPTLY"THE HOROPHONE " TIME SIGNAL RECEIVING

SETS FOR CLOCKMAKERS, being a complete receivingunit, write for particulars. Price 15 Gns. complete.

"STERLING" TRANSMITTERS, ex -Disposal Board, soiled,only requiring new contacts fitting to coils to make ready for use.Price £3 the complete set of components.

No. 1 VALVE SOCKETS. of Moulded Ebonite, each 516. No. 7,superior quality of Turned Ebonite,with necessary terminals, each716. (Why pay more ?)

HIGH VALUE RESISTANCES (non inductive) 80.000 Ohms,2 Megohms. each 916; 5 Megohms. each 1016.

AMPLIFYING UNITS OF EVERY DESCRIPTION builtto order with promptitude.

- BROWN " patent HEADGEAR from 120 to 8.000 Ohms in stock.SULLIVAN patent HEADGEAR from 2,000 to 8,000

February, taw. xxi Please mention the Wireless World


THEMARCONI INTERNATIONALMARINE COMMUNICATION

CO., LTD.

Wireless Operatorsrequired for ships ofMercantile Marine.Applicants must bephysically fit, aged 18to 2 5 years, and inpossession of 1st ClassP. M. G. Certificates.

Apply to The Traffic atanager,THE MARCONI INTERNATIONALMARINE COMMUNICATION

COMPANY, LIMITED,MARCONI HOUSE, STRAND, W. C. 2.

THE ZODIACTHE SUBMARINE

CABLE -SERVICE PAPER.News from the Cable Stations and Ships,illustrated with many interesting photo-

graphs and drawings.Monthly, 6d. ; or 6s. per annum,post free to any part of the world.

THE ZODIAC PUBLISHING COMPANY. LtdElectra House. Finsbury Pavement, London, E.C.

The Telegraph andTelephone JournalPublished Monthly in the interestsof the Telegraph and Telephone Service,

under the patronage of thePostmaster -General

PRINCIPAL CONTENTSOF JANUARY ISSUE

The London Trunk ExchangeBy J. F. ROONEY.

The Baudot (IV) By J. J TYRRELL.The Motor ExhibitionBy H. M. VINCENT.

Telegraphic Memorabilia.Fifty Years of Telegraphy.

" Hints to Telephonists on WritingPoetry."

EDITORIALS-The Retirements.

The Telephone Development of LargeCities.

PUBLISHED A rGeneral Post Office North, London, E.C. IPrice 4d. per copy, or 5/6 annually

MINERAL CRYSTALSFOR DETECTORS

Pure Zincite...6/6 oz. Galena ...6d. & 2/6 oz.Fused Silicon 2/- Iron Pyrites 6d. & 4/6 Copper Pyrites 6d. Bornite 9d. Molybdenite... 1/6 Carborundum 1/- Tellurium 2/6 piece " Radiocite," mtd.5/.Wood's Metal for fixing Crystals ... ...2/- Set of 9 Crystals and Wood's Metal. 5/- & 7/6Write Secretary, G.P.O. London, for permit to purchase.

RUSSELL & SHAW38, GREAT JAMES STREET,

BEDFORD ROW, LONDON, W.C. 1.

P. ORMISTON Ed SONS(P. H. ORMISTON) :: ESTABLISHED .793

79 Clerkenwell Rd., London, E.C."Ormiston, London." :: :: 13259 Central

Silk and Cotton Covered H.C. Copper Wire,Resistance Wires, Fuse Wire, Binding Wires,Charcoal Iron Core Wire, Asbestos CoveredWire, Braided and Twisted Wires, Bare CopperStrand and Flexibles of any Construction, WireRopes and Cords (fine sizes) in Galvanized Steel,

Phosphor Bronze, &c.

COMMERCIAL UNIONASSURANCE CO., LTD.

FIRE, LIFE, MARINE. ACCIDENT.Capital fully Subscribed ... ... ... 1,2,950000Capital Paid UpTotal Assets (including Life Funds)

Head Office: ;1st December, 1913 ... ... ... 124,902,25224. 25 & 26. CORNHILL, LONDON. E.C. Total Annual Income exceeds ... ... /8,5oo,ots0

The following classes of Insurance effected : FIRE, LIFE AND ANNUITIES, MARINE. LEASEHOLD REDEMPTION AND SINKINGFUND, ACCIDENT, including Personal Accident, Third Party, Burglary, Plate Glass, Fidelity Guarantee, Employers' Liability andWorkmen's Compensation, including Domestic Servants' Insurance. The Company also act as TRUSTEES AND EXECUTORS.

February, 192o. xxii Please mention the Wireless TVorld

WESTON ELECTRICAL INSTRUMENT CO., LTD.Audrey House, Ely Place, Holborn, E.C.

PATTERNS. PRICES, andMEASUREMENT FORMS

POST FREE

Telephone -139 CENTRAL

forWIRELESSUNIFORMSUP TO DIT8, write

SELF & SONUniform Specialists

RAILWAY PLACE (oppositeFenchurch St. Railway Station)

9, LONDON STREET, AND79, FENCHURCH STREET

LONDON, E.C. 3xxiik Please mention the Wireless World

SIMPLEFAULT TRACING forWIRELESS STUDENTS

and OPERATORSBy S. W. BROWN,

Late Practical Instructor to theMARCONI INTERNATIONAL MARINECOMMUNICATION COMPANY, LIMITED.This little book has been compiled to assistStudents of Radio - Telegraphy to obtaintheir P.M.G. Certificates on the StandardMarconi Apparatus. It will be foundextremely useful also for operators at seafor quick tracing of faults.

PUBLISHED BYJAMES MUNRO and Company, Limited

Nautical Publishers,15 & 60, Brown Street, GLASGOW

For germs apply to-LIEUT-COMDR. J. R. SCHOFIELD

M.B.E., R.N.V.R., (C). Principal.P.S. We have permanent situations waiting studentsimmediately they qualify.

ROBISON'S MANUAL ofRADIO -TELEGRAPHY& RADIO -TELEPHONY

(Fourth Edition, revised)By Comdr. S. S. ROBISON, U.S.N.,

and other experts.An excellent Textbook for Students & Operators.Thousands in use. Cloth 8vo. 256 pp. illustrated,

10s. net or 10s. 6d. Post Free fromS. RENTELL er CO., LTD.,36, MAIDEN LANE, LONDON, W.C.2

OFFICIAL ORGAN OF THE ROYAL

The ADVERTISER'SMEDIUM

AERO CLUB PREMIER &

LFIRST AEROWEEKLY INTHE WORLD

6d. WEEKLY

6Ve.4112.CRAFT:

ENGINEER,

Publishing Offices36. GT. QUEEN ST..KINGSWAY, W.C. 2Telephone : Gerrard 1828

Telegrams :" Truditur. Westcent.

London"

February, 192o. xxiv !'tease mention the Wireless World)

THE 1VIRELESS WORLD (Advertisements)

SOME PUBLICATIONS OF

THE WIRELESS PRESS LTD.12-13, Henrietta Street, Strand, London, W.C. 2

TelephonyWithout WiresBy PHILIP R. COURSEY, B.Sc. (Eng'g)

A.M.I.E.E.

PRICE 15/- NETPost free 15s. 6d.

Demy 8vo. Cloth. 249 Diagrams & Illustrations

THE

Oscillation ValveThe Elementary Principles of its

application to WirelessTelegraphy

By R. D. BANGAY.Crown 8vo. C 110 Diagrams215 pages. al.. Net & Illustrations

Post tree 5s. 6d.

THE

Thermionic Valveand its Developments in Radio -

Telegraphy and TelephonyBy J. A. FLEMING, MA., D.Sc., F.R.S., &c.

Demy 8vo. 144 Diagrams279 pages. 15/- Net & Illustrations

Post free 15s. 6d.

USEFUL NOTES ON

Wireless TelegraphyBy H. E. PENROSE.

Crown 8vo. 1 /4 each Post free I s 6d.

Book 1. Direct Current.Book 2. Alternating Current.Book 3. High Frequency Current and

Wave Production.Book 4. The 1 K.W. Ship Set.Book 5. The Oscillation Valve.

ALTERNATINGCURRENT WORK

An Outline for Students ofWireless TelegraphyBy A. SHORE, A.M.I.E.E.

Crown 8vo. Cloth. 163 Pages.86 Diagrams & Illustrations

Price 3/6 Net. P3sos Le.e

Standard Tablesand

Equations in Radio -TelegraphyBy BERTRAM HOYLE, M.Sc.Tech.,

A.M.I.E.E.A useful collection of Formulae. Equations andTables for every branch of Wireless Engineering

and ResearchPrice 9/- Net. Postage 6d.

The Wireless Telegraphist'sPOCKET BOOK

of Notes, Formula and Calculations.By Dr. J. A. FLEMING, M.A., D.Sc.,

F.R.S., M.Inst.E.E., etc.A valuable compendium for Wireless Engineers

and OperatorsPrice 9/. Net. Postage 5d.

Vacuum TubesIn Wireless Communication

By E. E. BUCHER.Second Edition. Demy 8vo. 178 Pages.

130 Diagrams & Illustrations

Price 9/- Net. Post free6d.

PRACTICAL

WirelessTelegraphyBy E. E. BUCHER.

Demy 8vo. 352 pages. 340 Illustrations

Price 9 . P st free/ 9s. 6d.

SEND FOR FULL CATALOGUEFebruary, 192o. );NV Please mention the Wireless World


USEFUL PUBLICATIONSfir ii WIRELESS BEGINNERMorse Code Card

Contains full alphabet, with punctuationmarks, figures, abbreviations, and contractions.Price 2d., post free.

Dictionary of Technical Termsused in Wireless Telegraphy.

By HAROLD WARD. Second Edition.Revised and Enlarged. Vest Pocket size.Contains over 1,500 definitions. Price 2s. 6d.net. (Postage 2d.)

The Elementary Principles ofWireless Telegraphy.

By R. D. BANGAY. In two parts. Price 3s.each. (Postage 4d.) Or in one volume,price 6s. net. (Postage 6d.) Invaluable forinstructional purposes. Used by H.M.Government.

The Maintenance of WirelessTelegraph Apparatus.

By P. W. HARRIS. An up-to-dateManual, full of practical hints and explana-tions. Diagrams of all ship installations, from

kw. to 5 kw. Price2s.6d.net. (Postage4d.)

Magnetism and Electricity forHome Study.

By H. E. PENROSE. Crown 8vo. Over500 pages. Contains a course of 50 Lessonsparticularly useful to the home student withoutprevious knowledge. Price 5s. net.(Postage 6d.)

Morse Made EasyLinen backed, for rapidly learning the MorseCode. Price 3d. net, or post free 3.4d.

Test Questions on WirelessTelegraphy.

Invaluable for self-examination. Price 2s. net.(Postage 3d.)Series 1. THE ELEMENTARY PRIN-

CIPLES OF WIRELESS TELE-GRAPHY. Part 1.

Series 2. COVERING THE GROUNDFOR THE POSTMASTER -GENERAL'S EXAMINATION.

Series 3. ELEMENTARY PRI NCI PLESOF WIRELESS TELEGRAPHY.Part 2.

Answers to above. 2s. net per series.(Postage 3d. each.)

The Handbook of Technical In-struction for Wireless Telegraphists.

By J. C. HAWK HEAD and H. M.DOWSETT. Second Edition. ThoroughlyRevised. Provides a complete theoreticalcourse for the Postmaster -General's certificateof proficiency. 344 pages. 240 diagramsand illustrations. Price 6s. net. (Postage 6d.)

THE MARCONI OFFICIAL GRAMOPHONE RECORDS

For Self -Tuition in Receiving Morse SignalsPrice 4s. each, double -sided. (Postage 9d.)

COMPLETE DETAILS UPON APPLICATION.

FOR HOME PRACTICE.

THE W. P. BUZZER SETConsisting of KEY BUZZER, BATTERY, AND CONNECTIONS

Specially made to suit the practice needs of theSTUDENT & WIRELESS AMATEUR

Brass Key on Ebonite Base, mounted on PolishedWood Box, containing Buzzer and Standard Battery - Price 1.1

Postage (eAtra) British Isles 6d., A brim I is. 6,1.1 0

The Wireless Press Ltd., 12-13 Henrietta Street, London, W.C.2February, 1920. xx\i Please mention the Wireless World


Aa VA L :711ILITArxr andSHIPPIJG OUTFITTEkS I:

REGULATION UNIFORMfor MARCONI OFFICERS.

-5- Miller, Rayner &Haysome

L-r-t LIMITED. ====

Head Offices :--110, FENCHURCH STREET, LONDON, E.C. 3

-.= LIVERPOOL -24, Lord Street.= SOUTHAMPTON -35-36, Oxford Street.=.f-- Telephone-Avenue 2995. Telegrams --- Milraysom, London =

ESTABLISHED 1818. --= 'Fs ' -..: - :,"

E----CONTRACTORS TO H.M. GOVERNMENT AND gam`4. ou't.7- THE PRINCIPAL STEAMSHIP LINES, ETC.=---=

COUBRO &SCRUTTONHead Office : 18, Billiter Street, London, E.C.

Telegraphic Address ; Coubro, Fen., London. Telephones : East 7, 7.16, 717

MAKERS OF

Wireless Masts and Accessories,Engineers and Smiths, Founders,Mast Makers and Riggers

CONTRACTORS TO ADMIRALTY, WAR OFFICE,INDIA OFFICE, AND COLONIAL GOVERNMENTS

Fehvuory. xxvii Pica, ih

THE WIRELESS

You are invited to read

THE

"Merchant Shipping Reviewand Empire Trade Gazette "

THE MONTHLY JOURNAL

For those interested in

Transport,Ship Construction,EngineeringandAviation.

To be obtained of all bookstalls, Newsagents,etc., at the principal ports at home and abroad,

or direct from the Publishers -

5, Richmond Street., Liverpool,and

19, Oxford Street, London, W. 1

PRICE - ONE SHILLING.

WORLD (Advertisements)"HOW TO BUILD

MENTAL POWER."'THIS remarkable new book by Grenville Kleiser tells you

how to train all the faculties of the mind, including Concen-tration, Memory, Judgment, Observation, Will, Imagination,and Constructive Thinking.

A careful study and proper application of this inspiringseries of lessons will lead you to great success and materialprosperity. You quickly learn how to

-acquire a retentive memory ;-develop and use will power ;-gain influence over people ;-argue, deduce, form sound opinions ;-think clearly and study intelligently ;-get at the real facts ;-increase your self-confidence;-overcome bad habits.

Although this course o, lessons is worth pounds uponpounds to anyone who uses it rightly, the price has been fixedvery net. "How to Build Mental Power," a wellbound volume of boo pages, with many diagrams in black andcolours, will be sent on three days' approval upon receipt ofthe special order form below.

Funk & Wagnalls Co.,134, Salisbury Sq., E.C.4

To FUNK & %MENUS CO., 134, Salisbury Sq., E.C.4,= Please send me on three days' anproval,post paid, "How teL'" Build Mental Power." If the book is satisfactory, I will remit

a.. within 5 days after receipt either x8/- in full payment, or 4/6p as first payment, and three further monthly payments of 4/6.

Name .M Address

Please Note New Registered Address

NORRIS, HENTY & GARDNERS Ltd.

" Gardner House,"115

QUEEN VICTORIASTREET, E.0 4

Telegrams-NORNODESTE

CENT -LONDON

Telephones-C I T Y-9493 and 9494

Branches -124, St. Vincent Street, Glasgow

Millburn House, Newcastle -on -Tyne701-802, Tower Builaing, Liverpool

66, Scottish Temperance Buildings, Belfast

Works :-PATRICROFT, LANCS., ENGLAND

February, 1920. xxviii Please mention the Wireless W orld


NIARCONI OUTFITS& NAVAL UNIFORMS

-BELTED NAVAL MACK READYFOR WEAR IN ALL SIZES

Blue Serges and Naval Cloths guaranteed to stand

SUN OR SEAAll Students from Any College Requiring Uniform should pay us avisit. Inspection and Price List Free. Enquiries from membersof the Marconi Company will convince you that we areRecommended for CUT, WORKMANSHIP AND FINISH.

OUR MUFTI DEPARTMENTis complete with all the latest novelties and designs in Suitings andOvercoatings, which can still be offered at our usual Moderate Prices.

URGENT ORDERS EXECUTED IN 48 HOURS

&H ELus CIVIL, NAVAL& MILITARYTAILORS ::

200 & 201, STRAND, LONDON, W.C. La,F, at:Z.

Send for the free bookon Standard InsulatingSpecialities. It con-tains particulars of

I Standard VarnishesandCompounds, methodsof application, tables ofquantities and detailsofthe results obtainableLet us send you a copy

in Standard insarating specialities axe regularlyused by abe lead4T: electrical warndarturinfirms, lighting and puler stations, railways,

trarovays,eic. VefinkeproofOrtheiroractiolutility

Catalogue and expert advice where necessary from

PINCHIN, JOHNSON & Co., Ltd.,GENERAL BUILDINGS, ALDWYCH, LONDON, W.C.2.

NDARDINSULATING

Varnishes fo Compounds

February, 192o.

Scientific AppliancesAll Materials for Electrical, Magnetic,

Optical and Experimental Work.

INSULATED WIRES and RESISTANCEWIRES of all sizes. SOLENOIDS,RELAYS, EBONITE and SUNDRIES

LENSES, PRISMS, MIRRORSfor making Microscopes, Telescopes, etc.

Our Famous WIMSHURST and otherSTATIC MACHINES High -NoteBUZZERS, KEYS, and COILS of all forms

ODD AND SECONDHAND P.O.INSTRUMENTS, GALVOS, andAPPARATUS at One -Third Cost.

Big Stock of Everything ExperimentalCall and inspect or write for new war -time list,

post-free Twopence.

FIFTY YEARS' EXPERIENCE.GOODS FORWARDED TO ALL PARTS.

Scientific Appliances(DALE and HOLLINS)

11-29, Sicilian Avenue, London, W.C.1


THE If 7 RE LESS TrORLD (Advertisements)

ESTABLISHED 1882

W. MACKIE COTHE P/1LACE EN,GISV_88`IISkCp WORKS

129,131,133, LAMBETH ROAD,LONDON, S.E1

TELEPHONE 182 HOP

Contractors to the AdmiraltyWar Office and Air Force

ELECTRICAL &MECHANICALENGINEERS

MANUFACTURERS OF MARCONI'SWIRELESS DISC DISCHARGERS, ROTARYCONVERTERS, DYNAMOS, ELECTRICMOTORS, TRANSFORMERS, BOOSTERS

Complete Electric Light Installations for CountryHouse and Ships. An Efficient Staff for Repairs

INVENTORS' IDEAS CAREFULLY AND SKILFULLY CARRIEDOUT FROM THE PREPARATION OF DETAILED DRAWINGSTO THE COMPLETION OF THE FINISHED ARTICLE

February, 1020. XXX ' Please mention the 'Fireless World

THE "FIRELESS WORLD (Advertisements)

The London Telegraph Training College Ltd.Telephone

WESTERN 2696. Morse House, Earl's Court, S.W. E S21-4Y3E-1:111t

OFFICIALLY RECOGNISED BY THE WAR OFFICE AND POST OFFICE AUTHORITIES

CABLE AND WIRELESS TELEGRAPHY.PARENTS desirous of placing their sons in either of the above Services and of affording them the

best training facilities should apply for particulars of Courses and the methods of instruction whichplace this Institution ii the first rank. Cable Telegraphy offers at the present time excellent

prospects to youths from 15 years of age and upwards, and the College has exclusive facilitiesfor obtaining posts for qualified students in the leading Cable Companies at commencing salaries of£140 to £200 per annum, with yearly increments of £12 to £25, and ultimate possibilities of

obtaining positions as Supervisors, Assistant Superintendents, Managers, etc.In the Wireless Telegraph Service the commencing remuneration at the present time is

approximately £150 per annum, and Operators, when qualified by obtaining the Postmaster -General'sCertificate of Proficiency, are nominated by the College for appointments.

No Correspondence Classes or Branches.DAY AND EVENING CLASSES.

An Illustrated Prospectus containing all information will be forwarded on application to

THE SECRETARY (Dept. H), 262, Earl's Court Road, Earl's Court, London,S.W.5Sole Proprietors of the " Scott - Training Disc which contains useful formulw and other informationfor Wireless Telegraph Operators and is invaluable to Army Signalling Officers for range finding, etc.

Price, complete with instructions for use, 1/-. Postage 2d.

WIRELESS TELEGRAPHYWIRELESS TELEPHONY &WIRELESS for AIRCRAFT

Young men wishing to enter a remunerative and pro-gressive profession should commence training as WirelessOfficers in the Mercantile Marine or the CommercialService. Fully qualified Operators are in demand,and first-class training is given at our Schools.A new field is opened up for ambitious young men inthe construction of Aircraft and Wireless EquipmentWe give special facilities to those wishing to studyin this branch Day and Evening Classes

THESE ARE THE ONLY SCHOOLS INGREAT BRITAIN FITTED WITH COM-PLETE STANDARD MARCONI, POULSENAND TELEFUNKEN INSTALLATIONSThese 'chool= are now fitted with a standardMarconi Valve Transmitter and Amplifying Receiver.

Write now fir Illustrated Prospectus

North-Eastern Schools of Wireless Telegraphy6. BLENHEIM TERRACE, LEEDSCENTRAL CHAMBERS. HIGH ST., SHEFFIELD18, ELDSON SQUARE, NEWCASTLE -ON -TYNEFebruary, Iwo.

Officine Elettro - MeccanicheSOCIETA ANONIMA£4,000,000 interamente versato

RIVAROLO LIGURE (ITALY)

WATER POWER TURBINESPELTON WHEELS :: REGULATORS

PUMPING MACHINERYof all types and for every service

ELECTRIC MOTORSHOISTINGMACHINERY

f

0 01

II II.

CRANES OFEVERY

DESCRIPTIONCAPSTANSLiFTs, ETC.Kindly send usyour enquiries

FULL ILLUSTRATED CATALOGUESAND PARTICULARS ON APPLICATION



MARCONIWIRELESSTelegraph Apparatus

for the

Mercantile MarineStations for Passenger, Cargo and other Vesselssupplied, installed and operated under Yearly

Maintenance Contract byTHE MARCONI INTERNATIONALMARINE COMMUNICATION Co. Ltd.

Full particulars upon application to the Company's Head Office at

MARCONI HOUSESTRAND, LONDON, W.C.2Telephone: City 8710 10 lines). Telegrams: "Expanse. Estrand. London."

NEWCASTLE.Milburn House, Newcastle -on -Tyne.

CARDIFF :8. New Street. CardiffTelephone: Cardiff 1501

LIVERPOOL:Agents-

JOSEPH CHADWICK & SONS801. Tower Building. Liverpool

Telephone : Central 487

ON -TYNE:Telephone: Central 1125

SOUTHAMPTON :Oxford Ho. Oxford St. Southampton

Telephone: Southampton 1818

GLASGOW:Agents-

MACNAUGHTAN BROS.175. West George Street. Glasgow

Telephone : Central 3107

February, 1920. xxxii Please mention the Wireless World


1920 DIARIES NOW READYTHE AMATEUR OPERATOR'S

Diary & NotebookPRICE 4/6 NET. POST FREE 4/10BEST LEATHER CASE, WITH TWO

THE WIRELESS OPERATOR'S

Diary & NotebookPRICE 4/6 NET. POST FREE 4/10

POCKETS, CARD & STAMP DIVISIONS

These Diaries represent different Interests, and have been prepared, withdifferent Sections to meet varying requirements. In addition to CharlesLetts & Co.'s Standard Diary, each Diary contains 32 pages of squared

paper for curves, &c. The Special Sections cover :-CONTENTS. CONTENTS.

Call Letters of Chief High -Power Stations.Gauges and Types of Wire used in WindingReceiver Coils. Conversion Factors and Data.Typical Valve Circuits. Amateur StationDirectory. Receiver Notes. Long Distance

Communications, &c., &c., &c.

Principal Wireless Stations on Ocean Routes.Table for Calculating Tolls on Messages.Some Typical Valve Circuits. Freak andLong Distance Communications. Best Adjust-ments of Receiver for Various Wavelength.'

&c., &c &c.

The Wireless Press, Ltd., 12-13, Henrietta Street,London, W.C.2.

Wireless OperatorsThere are many openings inH.M. Forces for trained WirelessOperators to serve at Home orAbroad. Minimum period ofservice two years, but this maybe extended.

For particulars as to rates of pay, etc., apply atnearest Recruiting Office ; or Central RecruitingDepot, Great Scotland Yard, London. S.W.

3d. TWICE MON I HLY

- - PHILATELICMAGAZINE

antklet/frthilirla,kparmieMCb/Lata2/4414,4 '

EDITED By Alt., 1-1 HARRIS

3d.

Largest and oldest independent stamp Journal. Fullof original articles and illustrations. 7/6 per annum,

4/.- for six months.Specimen 4.0 -page issue for 4.d. post free from-

"THE PHILATELIC MAGAZINE"II GOUGH SQUARE. FLEET ST.. E.C.

or of any newsagent.

February, 1920.

JIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIL

I WHIZZ-BANG1 E

is the title of anotherhandbook by theauthor of the famous

THEORETICAL PRINCIPLESOF WIRELESS TELEGRAPHY

It is a thoroughlycomprehensive text

book on

PETROL MOTORSOn sale at all

Messrs. W. H. SMITH & SON'SBookstalls, or at

= GEE & CO. (Publishers), LTD. =34 MOORGATE STREET, E.C. 2

PRICE ONE SHILLINGF11111111111111111111111111111111111111111MMMMIIIMifill11111111MMIIIIIF

xxxiii I'lease mention the Wireless World


Tel. Address- Telephone-Gardlocket. Fen, London:. 1650 Avenue 13 lines).

GARDNER, LOCKETand HINTON, LTD.

LONDON, CARDIFF, NEWCASTLE -ON -TYNE, GLASGOW, ETC.

Quotations and Specifications given forall descriptions of Welsh and other

Steam and Manufacturing Coals.Apply to Head Office

13, FENCHURCH AVENUE, E.C.3

OAK FLOORINGS.

HARDWOODS for HIGH-CLASS JOINERY

C. B. N. SNEWINand SONS, LTD.

BACK HILL, LONDON, E.C.

Here is THE electricalmagazine for you. For theDabbler and the How-te.make -it fiend. Chuck fellof experiments and thelatest electrical doings.Non - technical - in plainEnglish. One of theforemost authorities onWIRELESS in U S .200 illustrations. 90 bigpages. over 100

willanicles

One copyconvince you

Subscription rate 18S.a year ...ELECTRICAL EXPERIMENTER

Send for Free SampleCooe

GEOFFREY PARKER & GREGG(,2 8a. The Mall, Ealing, London. 'W.5

RADIO.NEWS

ScentsJULY

sacra

\SA

THE 100 PER CENT.Wireless MagazineThe Magic of Wireless iscalling. You can now hearwireless 'phone talk and re-ceive messages from the U.S.All about these and hundredsof other important things ofinterest to the Amateur are inthe Radio Amateur News.The greatest and biggestwireless magazine in U.S.Over 10) illustrations. 48 bigpages, and over 60 articles.

Nothing but Wireless.One Copy will Convince You.Subscription Rate g2'00 a YearSend for Free Sample.

Radio Amateur News254. Fulton Sr.. New York.

NewA n instrumentfor Rapid LearningScribo-Morse No. S. 167Scribo-Morse, No. S. 167, consists of arectangular polished mahogany box con-taining inside a buzzer and battery, andaffixed to the outside a metal plate havingthe Morse characters in relief, as shownwhite in the illustration, the remainder ofthe plate being heavily coated with anon -conducting material.

One end of the buzzer circuit is connected to the plate and the otherto a metal Pen by means of a flexible lead. By passing the Pen firmlyover the metal signs, each in turn will emit through the buzzer itscharacteristic sound, and thus the learner's ear will rapidly becomeaccustomed to the peculiar rhythm of each letter as he hears it.

GRAHAM & LATHAM, LTD., Military Engineers(Dept. W. 2), 27, LOTS ROAD, CHELSEA, LONDON, S.W. 10

February, 1920. Please mention the Wireless Toth)


A WIRELESSTRAINING

AT A CITY SCHOOL is a guarantee of the best possible Wireless' training. Efficient staff and thoroughly up-to-date methods. TheSchools at MANCHESTER, NOTTINGHAM and BIRMINGHAM are eachequipped with a standard 11 K.W. Ship Set, etc. Day 3 Evening Classes,also Postal Course. Students may join at any time. Fees moderate.

Special terms for 'Discharged and Disabled Soldiers and Sailors.

Full particulars and Prospectus on application to the Principal: Mr. I. R. HALLIWELL

CITY SCHOOL of WIRELESS TELEGRAPHY61, HIGH ST., MANCHESTER (Tel. CITY 5210).County Chambers, 66i, Corporation St., Birmingham.Guardian Chambers, 4, Bridlesmith Gate, Nottingham.

"The Model Engineer"A splendid paper for young Engineers. Apprentices,Students and Amateurs interested in Mechanics,Electricity and Model Making. It contains practicalarticles by experienced writers on Electrical andMechanical subjects. Locomotives, Motor Cycling.

Model Aeroplanes and Wireless Telegraphy.Published every Thursday, 4d. post free.

"Junior Mechanics & Electricity"The paper for beginners of all ages in Mechanics, Elec-tricity and Model Making. All the articles are writtenin simple language so that everybody can read andunderstand them. It is well illustrated. There is alsoa Queries and Replies section. from which much

valuable information can be obtained.Published on ist of each month. 4d, lost free.

SOME USEFUL BOOKS.Practical Lessons in

Metal corning ..Engineering Mathe-

matics Simply Ex-plained.

Practical Dynamo andMotor Construction

Practical InductionCoil Construction ..

Petrol Motors SimplyExplained ..

Workshop Wrinklesand Recipes

Small Accumulators .. reid.Electric Bells& Alarms raid.Electric Batteries .. roid.Small Dynatnos and

03 Motors . told.Induction Coils for

.9 Amateurs .. rofd.Small Electric Motors reid.

r,o Alternating Currents mid.Windmills and Wind

rq Motors.. ..sofd.Wireless Telegraphy

5,9 Simply Explained ..

Every Boy's Book of Electricity, 3d.Every Boy's Book of Engines, 3d.

Book List sent post free on receipt of card.PERCIVAL MARSHALL & CO.,66m, FARRINGDON ST., LONDON, E.C.

February, 1920.

VOURI UNIFORM

WILL COST LESSAND WEAR BETTERIF YOU GET IT FROM

pATERSON'SJ. & M. PATERSON, LIMITED

Naval & Marine Tailors,

301, ARGYLE STREET,GLASGOW.

EVERYTHING FOR OFFICERS' SEAWEAR.

SPECIALLY RECOMMENDED FORGOOD HONEST VALUE.



UNIFORM SUIT

PATROL SUIT

HARVEYS'Harvey Robertson

17, LONDON STREET,(FACING FENCHURCH ST. STATION'

HOSIERY DEPT. - - 15 London St.OUTFITTING DEPT., 16 London St.

LONDON, E.C. 3TELEPHONE AVENUE 2200

,Business hours - - 8.30-6Spturdays - - - 1.30Book to Mark Lane or Fenchurch St. Stations

TAILORS :: OUTFITTERSHOSIERS, AND TRUNK

(12AKERS

SPECIAL PRICESFor Wireless Operators, All Ranks

Uniform Serge Suit, good qualitygold lace and buttons, complete 126/ -

Superfine Cloth coat andtrousers, gold lace and buttons, 168/ -Bridge Coat, or Naval Warm,gold straps and buttons, complete 95/ -

Naval Cloth Cap, StandardBadge, complete ... 20 & 24/ -1st Wireless Cuffs 11/- Straps 5/ -2nd 10/- 4/ -3rd 5/- 3/ -

Standard Badges, best qualityEmbroidered Wreath 12/- 15/ -Buttons, Coat Size per dozen 3/-

1/6VestOIL COATS. NAVAL BELTED COATS.WHITE SUITS. AND EVERYTHING

FOR NAVAL WEAR

HARVEYS'Facing Fenchurch Street Station

Acknowledged to be the Best House:: for the Wireless Operator ::

MESS SUIT

GREAT COAT

February, 1920. Please mention the Wireless World

The OHMER INSULATIONTESTING SET (COX'S PATENT)This is the lightest, cheapest and best instrument of itskind on the market. It consists of an Ohmeter and Generatormounted in one case. The Ohmeter is of the Electrostatictype, giving extreme lightness. Absolutely unaffected byexternal fields. It reads directly in Megohms and is

independent of the voltage or speed of the generator.

NALDER BROS. & THOMPSON, LTD.,97a, DALSTON LANE, LONDON, E.8.

TWO GOOD WALLETSSolid Leather, size 6i X 4 when folded

"THE LONDON "-With space for photograph.Two roomy pockets. Two pockets for Treasury Notes.Space for cards and postage stamps.

"THE YORK "-With pull-out photograph holder.One tight pocket for Treasury Notes. One gussetpocket for letters. Card and stamp pockets.Price, either pattern, by registered post, 17/6 each.

EDEN FISHER & CO LTD.95, 96 & 97, FENCHURCH ST., LONDON, E.C.3

UNDERTAKE SUPPLY OF ALLREQUISITES FOR ENGINE ROOMS,POWER PLANT, MACHINE SHOPS, &c.

WRITE FOR ILLUSTRATED LISTS

W. H. Willcox & Co., Ltd.32 to 38 SOUTHWARK ST., LONDON, S.E. 1

Our Specially RefinedLubricants are in use onevery class of Machinery.

Registered " N1PHAN " Trade Mark

WATER - TIGHT PLUGS& CABLE COUPLINGSTO MEET HOME OFFICE REQUIREMENTS

5 to 250 Amps500 Volt Circuit

As used by H.M. War Office, Electric Supply CosRailway Cos., Marconi's Wireless Telegraph Co.

SIMMONDS BROS., LTD.,4, 6 & 8, Newton St., HOLBORN, W.C.P hones ; 2600 Gerrard

12061 CentralTelegrams "Niphon London"

Patented in Englandand Abroad.

COUPLING CONNECTING CABLES 3 -WAY TEE

February, 192o. Please mention the Wireless IT'orld

THE

WIDNESFOUNDRYCOMPANY, LIMITED. ESTABLISHED 1841

BUILDERS OF STEEL BRIDGES,PIERS, ROOFS, GIRDERS, & ALLKINDS OF CONSTRUCTIONALSTEEL AND IRON WORK.

Electrical Transmission Masts

CHEMICAL PLANT MANUFACTURERS SEGMENT AND PIPE FOUNDERS

CASTINGS OF EVERY DESCRIPTION

Contractors to the Admiralty, War Office,India Office, and Crown Colonies. Theleading British, Foreign and Indian Railways

Works

WIDNES, LANCS.

Telegrams : "Foundry, Widnes."

Telephone : No. 225 Widnes.

London gents :

GEORGE F. WEST & CO..13, VICTORIA STREET,

LONDON, S.W.Telegrams : "Westeelite, London."Telephone : 4340 Victoria.

Printed by Sanders Phillips s Co.. Ltd.. 6 & 8 Upper Thames Street, E.C. 4. for the Proprietorsand Publishers. The Wireless Press Ltd., 12-13 Henrietta Street, London W.C. 2 ; Sydney, N.S.W97 Clarence Street; Melbourne, 433/4 Little Collins Street ; New York, 25 Elm Street; Rome, via.Gregoriana. 36 ; South Africa. Exchange Buildims. Cape Town. and Central News Agency. Ltd.

XxX

Date post:	02-Nov-2020
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

nvhrbiblio.nl World/1920/Wireless... · PRECISION WIRELESS APPARATUS PATENT HIGH -RESISTANCE...

Documents