R. C. Cable WA6T LK52188 E. N uggetBeale CA 95903

Improving Heath's HT

- a hal f-dozen swell mods

carried out while the kit wasunder construction.

The firs t change consistedof installi ng a BNC-typeantenna co nnector in place ofthe 5/ 16" threaded bushingsuppl ied. I used the Am­phenol K-79-106 connectorfor this mod. I chose this par­ticular connector because ithas a slightly longer threadedshank which allowed thesoldering eyelet to extendinto the case for easy sol­dering. Some care mUH beexercised with thi s simple butuseful modification.

Unit ready for external PTT and private listening. Heathmicrophone element hod been installed in the Motorolahousing to keep the system matched.

54

A lthough it's an excel­len t two meter re­

ceiver /t rans mi tter, theHeath kit HW-2021 HT, I fe lt,could be made far more ver­sat ile through the em ploy­ment of a few minor modifi­cations. This article willdescribe some of th e manymodi fications possible withthis uni t. Listed are thosewhich I have perfo rmed onmy HT :1. The insta llation of aBN C-typ e ante nna connectorin place of the 5/16" th read­ed bushing.2. The use of the ex ternalantenna connector for anex t cr noll earp ho ne/spea kerjack.3. The use of RG- 174 co axialcable for the rf lead and thererout ing of the wiring to getrid of the rat's nest of inter­connec t ing wires betweencase halves.4. The installation of a push­to-talk (PTI) re lay.5. The addition of a :!:GOOk Hz crystal and crystalswitch.6. The addition of extra heatsinks to the rf transistors.

Some of these modifica­tions came about whileassembling the rig, othersfrom on-the-air usc, and stillothers because of componentfailures. I' ll start with thefirst group - those cha nges

A problem arose, for me atleast, in that there is only halfof a hole in which to installthe connector. This, ofcourse, is due to the fact thatthe connector and all of theoperating controls - channelswitch , squelch, and on /off/volume - are mounted on thecenterline along the top ofthe unit where the caseseparates into two halves. Thesolu tion I fo und was actuallya compromise. In place of theloc k was her supp lied with theco nnector, I installed thelargest flat washer I had inmy hardware stock thatwould fit the threaded po r­tion of the connec tor snugly.Thi s allo wed me to tight endown the nut and Squeeze theedge of the hole between thewasher and the flange on theconnector. However, uponbearing d own on the nut toget a secure insta llation , thewashe r cocked slightlytoward the to p of the unit.This then prevented the casefron t fro m being installedproperly. To get around this,I used a fairly sharp pocketknife to shave away a smallamount of the plastic casealong the inside edge of theconnector hole in the speak­er /mike half of the case. Thecase is thermoplastic, and,with a little trial and error, agood fit of the two casehalves was possible.

Once this modificationhad been accomplished, thenex t one was logical - theuse of the external antenna

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Fig. 1. External speaker/earphone hookup using the externalantenna jock.

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Since one side of th e crystalwent to grou nd, o ne ho le wasdrilled lust large enough forthe pin [ 0 fi t and the pin wasthen soldered to the PCboard. I was ab le to do thisbecause the area in which thecrystal is installed is a fair lylarge ground pad and no extrawiring was needed. The holefor the o ther crystal pin wasenlarged to ensure the pin didnot come into contact withthe foil o n either side of theboard. To thi s pin was sol­dered a sho rt piece of small­gauge wi re which in turn wasrouted up to the componentside of the board through asmall hole drilled for thatpur pose. Th is wi re was thencon nected to the new ±600kHz switch.

After these changes werem ade, I had two smallswitches o n the lef t side ofthe HT in place of the o nelarger switch - o ne to selectsimplex or offse t and theo ther for either +600 kHz o r-600 kHz. I chose to have the

the smaller replacementsfir mly and too shallow toallow the case halves to bemated with the switches inplace. The fir st prob lem wassolved by slid ing into thespaces at each e nd of theswi tch es small pieces of metalcut from the shan ks of twosma ll ground lugs. The secondproblem was so lved by fil ingthe ho le larger. Being softther mo plast ic, this took asmall amount of effor t, andthe bottom of the hole wassoon even with the PC board.The tab o n the fron t half ofthe case also had to be fileddown even with the caseedge. This took care of theswitch mounting problems.

Mounting the crystal camenext. Th is was no real pro b­lem at all, for, with the largeroriginal offset switch re­moved , adequate room wasgained to allow the crystal tobe moun ted next to th e newswitches. First, two smallholes were drilled through thePC board fo r the crystal pins.

Fig. 2. Schematic of the o ffse t oscillator with the addition ofan 11.3 MHz crystal, giving a ±600kHz offset option.

The external microphone adopter mentioned in the text andthe 5PST switch aided to the battery charger boord. Thenotched battery charger connector is plugged in, showing howthe notch keeps the switch from functioning during batterycharging,

cable at the time of assembl y.This type of coax was alsoused to co nnect th e BN Cco nnector to the circuitboa rd. I found it far easier towork with than that suppliedby Heath with no adverseresults.

T his bri ngs me to the nextgroup of modifications, tho sewhich resulted from actualuse of the unit. The first wasthe addition of a plus orminus 600 kHz fu nct io n tothe HT. The crvstal suppliedwith the un it al lows for on lya minus 600 kHz offse t of thetransmit freq uency. This Isa cc ompli shed by pus hingdown the offset switch on th eleft side of the unit, By doingthis, you are selecting a 10.1MHz crvstal and discon­nec ti ng the 10.7 MHz crystalused for direc t or simplexoperation. By selecting this10.1 MHz crystal, you arelowering the offset oscillatorf requency b y 600 kHz. Th iso scilla tor , in turn, suppl iesone of th e two signals that goto the transmitter mixer,Q21 . If this frequency israised or lowered, th e trans­mitter frequency is raised orlowered a like amoun L Thus,to gain a plus 600 kHz offset,an 11.3 MHz crystal is re­quired. These can be acqu iredf rom any crystal manufac­turer for arou nd $10. Buthow do you select one ofthree crystals using a switchhaving only two positions?

I d id th is by getti ng rid ofthe switch. In place of theoffset switch provided withthe unit, I installed two SPOTsubmi niature switches, Elec­trocra ft 35·202. Th eseswitches fi t nicely in to thereta ining slo ts prov ided forthe original switch, but, asusual, all was not well. Ifound th e slo t for the o rigi nalswitch to be too long to ho ld

jack as an external speaker!earphone jack. (See Fig. 1.)This comes in handy when Iam using the unit, in conjunc­tion with a trun k-mounted5/8 whip, as my mobile rig. Ican carryon a QSO or moni­tor the local repeaters with­out bothering the spouse withthe consta nt chi tchat andsquelch tails that fill theTovota. Of course, whenalone, I use the speakerattached to the broadcast re­ceiver installed in the car.Here I simpl y added twowir es directly across thevehicle's speaker, broughtthem out to the app ropriatelength , and added a miniaturephone plug. No switchingbetween the broad cast re­ceiver and HT is employed,and no adverse results havebeen no ted.

Not uslng this jack for itsintended purpose addedgreatly to the nex t change Ifelt was in line. T his was thereduction of the rat's nest ofwire that resulted when itcame time to mate the twocase halves. Originally, toclose the un it, a total of tensepa rate connect ions had tobe made. By elim inating theexternal antenna jack fun c­tion from the fro nt side ofthe case, four of these con­nections wer e removed. Al so,'f you use miniatu re shieldedcable for the microphoneco nnections, no coax will beconnected to th e fron t side ofne case. This results in a.mall bundle of wires con­rec ting the case halves. Thisnm dle, when laced together,dves better access to thentemal workings of the un itrnd makes it far easier toeparat e and mate the twoase halves. I, however, usedtG·174 coaxial cable fo r mynike connectio ns, not havingny small shielded aud io

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Fig, 4. Schematic of battery charger with the adapter actuatedSPST normotty-ooen switch connected across 0 304.

Fig. 3. The PTT schematic. The diode across the relay coil canbe any silicon diode, such as a TN45 7.

Overall view of most of th e changes. The BNe antennaconnector, tl«) new o ffset oscillator switches and crystal,reduced tangle of interconnecting wires, the double heat sinkon Q26 (round black object in center) with the two aluminumtubing heat sinks on Q24 and 25 to the left of Q26, and thePTT relay to the right of Q26.

56

switch toward the back of theunit the simplex /offset swi tchwith the down po si tio n beingthe offset position and upbei ng for simplex . The frontswitch then became the ±600kHz s witch , with the +600kHz being the up positiona nd the -600 kHz being thedown position. The hookupfor the switches is shown inFig. 2.

The next modification(PTT) came about for tworeasons. One was that I useth is unit as an HT, horneQTH rig, and for my mobilerig. In other words, it is myone and only two meter rigand I got tired of having to

pick up the entire radio eachl ime I wanted to say some­thing. Th is was aw kward d ueto th e size of th e th ing (itgets heavy after a few ex­cha nges) and the traili nge xterna l antenna and speakercables. The other reason wasthat I wanted to see if itcould be done with no ma jorrewi ring o f the rig.

The fir st problem was howto connect a microphonewith a PIT switch to theinter na l workings of the rig.Thi~ .was done by using t hetwoex tra pi ns on the batterycharger co nnector o n the rearof t he set. O ne became audioin, one the PIT key line , an d

th en I ran o ut o f pins. To getaround this and still not haveto add another connector tothe rig, which was one of m yaims , I borrowed one o f thebattery charging pins openwhen th e unit is being usedwith the external micro­phone. To do this req uiredthe addition of a simple SPSTnormallv-opcn switch to thebattery charger board in thebottom of the HT . Th isswitc h, when actuated byplugging in the m icrophoneada p ter, sho rts out D304 inth e battery charg ing circu it,thus giving me a third wirefor the ground return need edfor the PIT relay and th eshield of the mi ke cable. Thisis shown in Fig. 4 . To preven tthis s w it c h fro m beingac tuated when the batteriesa re being charged, a notchwas cut in the corner o f th ebattery charger connector tokeep it from coming intocontact with t he switc hmechanism. The switc h its elfcam e from a relay in the junkbox . A mlcroswltch woulddo, as well as any number ofo ther switches.

O nce t hese mechanical ,problems were overco me , themodifi cation to the electroni cport io n of th e unit was nomajor undertaking. First asmall DPDT 12-volt de relaywas selected to do the switc h­ing. The relay shown wasused because I could not finda subminiature relay that Icould mount di re ctly on thePC board and because I had adozen of them in the junkbox. This relay drew about

35 mA at 12 volts, so I felt itwould not greatly add to th ebattery drain. The next stepwas to find a place and meansto mount the relay. I c hosenot to mount th e relay at all.Instead, the relay is held inplace by the seven wires so l­dered to its terminals an d bythe pressure of a piece offoam rubber I ad ded to th efront of the uni t . Th is foa mkeeps the relay in place anda lso keeps the ba ttery packfrom rattling. The loc ation ofthe relay was chosen, asshown, so tha t it wou ld beclose to th e aud io input ter­minals on the PC board andbecause it sa t nicely o n top ofcoils L1 and L22.

No w, to switch th is rigfro m rece ive to transmit usingan external PTT s wi tch , tworequire ments have to be met :Twel ve vo lts must beswitched from the receiver tot he transmitter. and themicrophone in pu t pin F o nthe PC board has to beswitc hed from the internalmike to th e extern a l mike.The int ernal microphonemust be di scon nected to pr e­vent it fro m picking upextempora neous audio a nd toprevent the input impedanceof the audio amp lifier frombeing upset by having twomicrophones connected to itin parallel.

As I sa id , this rewiring wasnot a major u nder t aking. Istarted with the +12 voltsswitching. First I removed thelead connecting the PC boardto terminal 3 of th e PCboard-mounted PIT switch,

Oose-up of the added 11.3 MHz crystal and two new slideswitches. Only one piece of wire was added; all other leads arethose disconnected from the original offset switch.

Close-up of SPST switch added to charger board with externalmicrophone adapter plugged in actuating the switch, shortingout D304. Resistor shown was for test purposes only.

gether. Th is addit ion effec­tively doubled the coolingcapacity available. That tookcare of 026.

024 and 25 were a lit tlemore d ifficul t, and, again, aco mp ro mise had to beaccepted. First. I tried somestore-bought TQ.18 slip-onfinned heat sinks, but thesetwo tra nsistors are sur­ro unded by coils and resistorsand the fin s were alwayshitti ng someth ing. I thentried some home-brew finnedheat sinks, but they wouldn'tstay in place and agai n weretoo close to the o ther corn­ponents for comfort.

I then hit on the idea ofusing some thick-walledaluminum tubing as a simplesli p-on heat sink. They aren'tfinn ed or in any fancy shape,

chec king a ll voltages and cur­rents, I decided that heat wasmy villain.

026 is provided with aslip-on round heat sink, while024 and 25 are o n their ownas far as heat dissipat ion isconcerned. To try to cooldown 026, the power ampli­fier transistor, I first obtainedfrom Heath another heat si nklike th e one supplied with theki t, part num ber 215-45, at acos t of 554. I then bentinward the portion of theheat sink that normally fitso nto the transistor body untilit was small eno ugh to f itinside of the top of th e in­stalled heat sink. Then aliberal amount of siliconetransistor grease was used tofill any gaps, and the twoheat sinks wer e pressed to-

•the Heath element.As for wi ring, all tha t was

lef t then was to hook up thesup ply voltage and contro lline for the PTT relay. The+12 volts for the relay coilwas obtained by running awire from pin 1 of the PCboard PIT switch to o ne sideof the rel ay coil. The key linefrom the other side of therelay coil was then routed,along with the existing bat­tery wi res and the new micro­phone inpu t cable, to thebattery charger con nec to rwhere it was connected to thelast unused pin. To provideclearance for these new wires,which must run over thebattery charger ho lder. asma ll notch was cut in thetop of each end of the holder.Also, a kickback diode shouldbe connected across the relaycoil. I placed mine physicallyo n the battery charger board,con nec t ing it from the PTTkey line to the + term inal onthe board. This had the sameeffect as putting the diodedirectly on the relay butsaved me the hassle of solder­ing in a crowded area. Be sureto watch the polari ty withthe cathode going to the +terminal. The relay hookup isshown in Fig. 3. This PITsche me has no w been usedfor over eight months with nopro bl ems encountered. Ho w­ever, other problems havedeveloped , and this brings meto the last modificatio n,which actually is an addi tio n.

From the time I first gotthe rig o n the air. it seemedto me that transistors 024,25, and 26 ran unreasonablyhot. Ho wever, a chec k ofanother 202 1 showed thesame condit ions, so it wasco nsidered normal. Rightafter this check, however, theHT used for comparisonfailed and Heath resol ved theproblem by re placing 024a nd 25. This made mewonder if indeed this was anor mal condition. Mysuspicions were furtheraroused when 025 in my rigfailed du e to a collector-to­base short. To me, thi s meantsomething was not right.After replacing 025 and

SW1. To this lead, I con­nected a wire leading to oneof the nor mally-c losed con­tac ts of the new PIT relay.From termi nal 3 of the PTTswitch, I ran a wire to thearm of the same relay half.This left the normally-openpi n of the relay, which wasthen connected to terminal 2of the board- mou nted PTTswitch. That completed thede switching change. Nowwhen the relay is energized,the de to the receiver is int er­rupted and switched to thetransmitter. Wh en not in use,the relay just sits there andthe board -mounted PITswi tch does the work.

The audio wiring changeswere equa lly as simpl e. First Id iscon nec ted the audio cab legoing to pin F on the PCboard. A short piece of wirewas then used to con nect pinF to the unused relay wiperarm. To the no rmally-closedcontact of this half o f therelay, I connected the in­ternal microphone cable.These two connections weremade using the extra wireconnector pins a nd soc ketssuppl ied with the kit. Finally.a small shielded cable wasconnected to the last unusednormally-open contact of thePIT relay. Th is is the sidethat goes to o ne of the un­used pins on the batterycharger connector and carriesthe ex t emal microphoneaudio into the unit. One endof the shield o n this cable wascon nected to p in Y (ground )on the PC board, and theother end was connected tothe negative (-) battery ter­minal on the battery chargerPC board.

I would like to mentionthat just about any micro­phone will work as an ex­ternal microphone. but, tokeep everything matched asHeath did, I ordered a re­placement element and in­stalled it in my microphonehousing. Before doing this. Iwould get reports of beingtoo tinny o r too bassy fromthe local group. But nowthere is no d ifference be­tween the internal andexternal audio quality using

57

but they do conduct heatwell and that is what I wasaf ter. Th e tubing I used h adbeen a one- inch-long spacerthat had been str ipped fro msome pi ece o f equipmentsome time ago. First, usingthe appropriate size dri ll bit, Islowly enlarged the hol e ineach end of the spacer unti l itwould fit about 9/10 of theway over the transistors. Ithen cu t th e spacer in halfand painted th e two piecesfl at black.

Again using si licone greaset o increase conduction and toact as a lubrican t, I lightlyt aped the heat si n ks onto thetwo transistors. For thepurists, th ese pieces o f tubingwill change the tuning of thecollec tor ci rcuits since thecollectors of these transistorsare connec ted to the metalcases of the transistors. But Ifound it to be such a smallchange th at it wasn 't worthbothering with . Possibly ifthe lengths of tubing were

made longer , problems coulddevelop, but these half -inchsect ions don't see m to createany electr ical degradation anddo carry away some of theheat, I don't know what the irthermal resistance is or th eird issipation capacity, but Ih aven't had a tran sistorfailure since I installed them,so I f eel they have solved theproblem.

That sum s up the ch angesI have made to my HT. I haveseveral o thers in the long-

range planning stage, such asa synthesizer and channelscanner, but these are goingto take time to complete.With this rig, any number ofaddi tions can be made easily.The circu i try is not complexand plenty of room is avail­abl e for several addi t ions tofi t into the case. So, if youhave an HW-2021 and think itcou ld be a b it more versat ile,rnake a few changes andenjoy your rig that much

more. -

Continued on page "8

should be rad io and not flyingor computers or butterfly cot­lecting . But I always enjoyedyour dad 's co lumn on "an­ci ent" aviating, and I think it'smore th an coinci dence. Itseems to me that f lying andamateur rad io are related inthat they both have to do with ahigh ly technical area of pron­ctency-ett should be no eccr­dent that a pil ot/ham is li kely tobe one and the same person. Inspite of what you think of theFCC, it has always seemed tome that the FAA and the FCCare a large cu t above the usualbureaucracy, and it is for thesame reason in each case:They deal in an area of teen­nical expert ise, not merely int he administration of pork­barrel projects. I think it's notmerely co incidence that WorldRadio News carries a regularfeature about flying and ama­teur radio, while not botheringto focus on amateur radio inbutterfly collecting.

For myself, I haven't any usefor the myr iad of computer ar­t ic les I see in your book, butwith more than 200 pages tothe issue, I can skip over 90percent of the contents andstill get my money's worth.

As for t he materials onbeating the cops, etc., let mecommend you on a publ ic ser­vice of true professional four­nali sm. Lesser publisherswould just be Interested inkeeping their subscribers hap­py. Your approach to exposingthe wrongs in government andqovernment-sponsorec privatemonopolies like the telephonesystem represents the highestc alli ng o f const itutionally,protected free speech . Thealternative to publish ing is tolet th ings smolder until theyreally get so bad as to erupt ln.to open revolution . That's thetheory of a free press-that wemay con stantly keep our eyeon things and hopefully there­by keep the society on an even

CONGRATULATIONS

In regard to the recent stri ngof tetters you've publ ished tak­ing you to task for your maga­zine's contents , " Let me saythis about that" : I know thesubstance of a radio magazine

1_--1

Moses leading us all to greenerpastures. I realize that the CBis the stepch ild. The reason forth is is the FCC fail ure ingeneral and the hams' stut ti ­ness, let's face it! When CBbecomes tuu-crown and hasbeen around as long as ama­teur radio, there is no tellingwhat may happen.

They are both needed in thisday and age; we should allwork together for a more solidunderstand i ng -help oneanother, not sit back and lookdown our noses and back -stabeach other . Amateur radio hasits place for the long calls, hob­by act ivit ies, and hel p inemergenc ies, but so does theCB on the local scene-high·way information, help for astranded lady with a flat t l re,and the good work of theREACT group. The HighwayPatrol has had more help fromthe CBers than the hams, andwe all know It.

The rad io is a part of life thatis here to stay, so let us all useit and its aspec ts to form acommon bond to help all man­kind, not have a private hassleon who should and who shouldnot.

I w ill now get off the soap­box and let you have it back. Ihope you will use your in­fluence to help both phases ofour freedom of speech, andchannel it to the benefit of all.

I do hope you will print th is,as it is about t ime we took along look at ourselves.

I am in the process of gettingmy ham ti cket so I may enjoyth e best of both modes.

Jim Foustliberty MO

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THE CHOSEN FEW

I am one of your avid readersand enjoy 73 MagaZine verymuch. In reading your ecrto­rials, I fi nd them in the mostpart very inform ative, butsomewhat bi ased.

I cannot understand whatyour hangup is against CBers,but it is chronic. I have to agreethat the 10 meter band is beingunduly penalized by the FCC. Ifeel they are going abou t it t hewrong way; it seems It's likecutti ng off the child's thumbbecause he sucks it.

Now, back to the problem ofCB versus amateu r rad io ,un less things have changedsince I have wrt t ten you thisletter. There are bad mannersand ratc het jaws l ike youwouldn 't believe-try any ci ty 2meter band. As for inso lenceand bad manners, just try a netcheck-In. I am ashamed to sayit, but some of those so-call edchosen ones thi nk they are

license. Superior publ ic servicecan be provided on these cv r­rently semiprivate frequencies.

Only th ing that is needednow is a national coordinationof these frequencies on theGMRS band, so citizens canuse repeaters in other com­muniti es. I hope peopl e don' tthink I'm down on ham radio. Ienjoy OXing an d " rad ioscout ing: ' but I don 't enjoydefens ive VHFers wor riedabout someone else using arepeater 300 MHz away.

Dave Sweigert WB9VKOFort Wayne IN

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was happy about my attemptsto help a bona fide emergencygroup.

Hams should wake up. Peo­ple are entitled to good com­munications, better than CB. Ifamateurs want to fight move­ments In the GMRS area, theycan ki ss publ ic support of ourhobby good·bye. Radio arne­teurs should understand weare very lucky to have our fre­quencies and our hobby. Ourknowledge should be sharedw ith the c ommu nit y , notlocked away in the ham shack.

Since Jan uary, the licensewas granted and the repeaterwas put on the air. But I lostmany friend s and assoc iateswho thought I had " sold out"ham radio. To rep lace thosecrusty hams, I have gained newrelationships with the GMRSusers, including a doctor,lawyer, and several emergencymedical technicians. These areno t your t yp ical d ie-hard27·MHz users.

I could care less what hap­pens at the WARC, as long asGMRS frequencies remain in­tact. Radio amateurs are turn­ing a hobby into a professionallifestyle, with expensive equip­ment , l inears, and towers. Let 'sremember the fun and excite­ment of a breadboard and in­verted vee on the Novice band.

Many hams should considerwhether or not to help groupstr y ing t o s t a rt a GMRSrepeater. Li ke WA4EOX pointsout , if a tw o me te r c luboperates a Class A repeater,non-heme can join in the funwithout worrying about a

from page 12

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