Technician License Class Gordon West Technician Class Manual Pages 150-159 Antennas Presented by...

Technician Technician License ClassLicense Class

Gordon West Gordon West Technician Class ManualTechnician Class Manual

Pages 150-159Pages 150-159

AntennasAntennas

Presented byPresented by

Heart Of Texas Heart Of Texas Amateur Radio ClubAmateur Radio Club

(HOTARC)(HOTARC)

AntennasAntennas 22

AntennasAntennasPages 150-155…Pages 150-155…

Key words:Key words:

– Rubber duck Rubber duck poor performance poor performance

– Vertical and horizontal antennasVertical and horizontal antennas

– ½-wavelength formula: 468 ½-wavelength formula: 468 ÷÷ f f

– ¼-wavelength formula: 234 ¼-wavelength formula: 234 ÷÷ f f

– Directional antennasDirectional antennas

First, let’s look at the basics about antennas…First, let’s look at the basics about antennas…

Antennas 3

Antennas: The DipoleAntennas: The DipoleSize of the antenna is based on the frequency, or the wavelength, .

38.5 in.½ Length (in ft) = 468/f where f=freq in MHz

Example: for f = 146 MHz

Length = 468/146 = 3.2 ft, or 38.5"

A “half-wave dipole” has length equal to ½ the wavelength.

Antennas 4

Antennas: Vertical “Whips”Antennas: Vertical “Whips”Vertical whips are often attached to a magnet.

So, they are often called “a “mag-mount.”

Typically, they are ¼ wavelength.

¼ Length (in ft) = 234/f where f=freq in MHz

Example: for f = 146 MHz Length = 234/146 = 1.6 ft, or 19.2“

Some whip antennas are 5/8 wavelengths: they radiate at slightly lower angles.

Antennas 5

Antennas: “Beams”Antennas: “Beams”Parallel “dipoles” strengthen the signal in one direction.

They “beam” the radio signal in one main direction.

They also receive signals of the design wavelength more effectively from that direction, and “reject” signals from the opposite direction.

Different directional designs: Yagi, quad, dish.

Antennas 6

Antennas come in all shapes!Antennas come in all shapes!

AntennasAntennas 77

T9 A04 T9 A04 (pg 150)(pg 150)

What is a disadvantage of the What is a disadvantage of the "rubber duck" antenna supplied "rubber duck" antenna supplied with most hand held radio with most hand held radio transceivers?transceivers?

A.A. It does not transmit or It does not transmit or receive as effectively as a full sized antennareceive as effectively as a full sized antenna

B.B. It is much more expensive than a standard antennaIt is much more expensive than a standard antenna

C.C. If the rubber end cap is lost it will unravel very If the rubber end cap is lost it will unravel very quicklyquickly

D.D. It transmits a circular polarized signalIt transmits a circular polarized signal

AntennasAntennas 88

T9A10 T9A10 (pg 150)(pg 150)

What is a good reason not to use a "rubber duck" What is a good reason not to use a "rubber duck" antenna inside your car? antenna inside your car?

A.A. Signals can be 10 to 20 times weaker than Signals can be 10 to 20 times weaker than when you are outside of the vehiclewhen you are outside of the vehicle

B.B. RF energy trapped inside the vehicle can distort RF energy trapped inside the vehicle can distort your signalyour signal

C.C. You might cause a fire in the vehicle upholsteryYou might cause a fire in the vehicle upholstery

D.D. The SWR might increaseThe SWR might increase

AntennasAntennas 99

T7A03 (pg 151)T7A03 (pg 151)How can you make the signal from a hand-held How can you make the signal from a hand-held radio stronger when operating in the field?radio stronger when operating in the field?A.A. Switch to VFO modeSwitch to VFO mode

B.B. Use an external antenna instead of the Use an external antenna instead of the rubber-duck antennarubber-duck antenna

C.C. Stand so there is a metal building between you and Stand so there is a metal building between you and other stationsother stations

D.D. Speak as loudly as you canSpeak as loudly as you can

AntennasAntennas 1010

Vertical and Horizontal TerminologyVertical and Horizontal Terminology

Perpendicular to the earth Perpendicular to the earth is “vertical.”is “vertical.”

Parallel to earth is Parallel to earth is “horizontal.”“horizontal.”

Vertical antennas radiate with Vertical antennas radiate with “vertical polarization,” and “vertical polarization,” and should match the orientation should match the orientation of antenna at the other end of antenna at the other end of the radio link. of the radio link.

Earth

perpendicular

Earth

parallel


Size of AntennaSize of AntennaBasic half-wavelength dipole formula:Basic half-wavelength dipole formula:

Example: For 146 MHz…Example: For 146 MHz…

““Quarter-wavelength vertical” would be ½ the length of the Quarter-wavelength vertical” would be ½ the length of the half-wavelength dipole, so formula becomes:half-wavelength dipole, so formula becomes:

Hint: Use rough approximations for T9 A11 and T9 A12. Hint: Use rough approximations for T9 A11 and T9 A12. – ½-½- dipole for 2 meters would be 1 meter (or about 39 inches). dipole for 2 meters would be 1 meter (or about 39 inches).

– ½-½- dipole for 6 meters would be 3 meters (or about 117 inches). dipole for 6 meters would be 3 meters (or about 117 inches).

468 ft(in MHz)

Lengthfreq

Half - wavelength dipole :

468 fte: 3.2 ft

146 MHzLength Half - wavelength dipol

234 ft(in MHz)

Lengthfreq

Quarter - wavelength vertical :


T9A02 T9A02 (pg 151)(pg 151)

What is an antenna that consists of a single What is an antenna that consists of a single element mounted element mounted perpendicular to the Earth's perpendicular to the Earth's surfacesurface??A.A. A conical monopoleA conical monopole

B.B. A horizontal antennaA horizontal antenna

C.C. A vertical antennaA vertical antennaD.D. A traveling wave antennaA traveling wave antenna

Earth

perpendicular


T9B08 T9B08 (pg 151)(pg 151)

What can happen if the antennas at opposite What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are ends of a VHF or UHF line of sight radio link are not using the same polarization?not using the same polarization?A.A. The modulation sidebands The modulation sidebands

might become invertedmight become inverted

B.B. Signals could be as Signals could be as much as 100 times much as 100 times weakerweaker

C.C. Signals have an echo effect Signals have an echo effect on voiceson voices

D.D. Nothing significant will happenNothing significant will happen


T9A09 T9A09 (pg 152)(pg 152)

What is one type of antenna that What is one type of antenna that offers good efficiency when operating offers good efficiency when operating mobile and can be easily installed or mobile and can be easily installed or removed?removed?A.A. A microwave antennaA microwave antenna

B.B. A quad antennaA quad antenna

C.C. A traveling wave antennaA traveling wave antenna

D.D. A magnet mount vertical A magnet mount vertical antennaantenna


T9A11 T9A11 (pg 152)(pg 152)

What is the approximate length, in What is the approximate length, in inches, of a inches, of a quarter-wavelengthquarter-wavelength vertical antenna for 146 MHz?vertical antenna for 146 MHz?A.A. 112 inches112 inches

B.B. 50 inches50 inches

C.C. 19 inches19 inchesD.D. 12 inches12 inches

234 ft1.60 ft

146 MHzLength

12 in.

1 ft 19.2 in.


T9A06 T9A06 (pg 153)(pg 153)

What is the advantage of 5/8 wavelength over What is the advantage of 5/8 wavelength over 1/4 wavelength vertical antennas?1/4 wavelength vertical antennas?A.A. They are easier to match to the feed line than other They are easier to match to the feed line than other

typestypes

B.B. Their radiation pattern concentrates Their radiation pattern concentrates energy at lower anglesenergy at lower angles

C.C. They pick up less noiseThey pick up less noise

D.D. Their radiation pattern concentrates energy at Their radiation pattern concentrates energy at higher angleshigher angles


T9A03 T9A03 (pg 153)(pg 153)

What type of antenna is a simple dipole mounted What type of antenna is a simple dipole mounted so the elements are so the elements are parallel to the Earth's parallel to the Earth's surfacesurface??A.A. A ground wave antennaA ground wave antenna

B.B. A horizontal antennaA horizontal antennaC.C. A rhombic antennaA rhombic antenna

D.D. A vertical antennaA vertical antenna

Earth

parallel


T9A05 T9A05 (pg 153)(pg 153)

How does the physical size of half-wave dipole How does the physical size of half-wave dipole antenna change with operating frequency?antenna change with operating frequency?A.A. It becomes longer as the frequency increasesIt becomes longer as the frequency increases

B.B. It must be made larger because it has to handle It must be made larger because it has to handle more powermore power

C.C. It becomes shorter as It becomes shorter as the frequency increasesthe frequency increases

D.D. It becomes shorter as the It becomes shorter as the frequency decreasesfrequency decreases

Half-wavelength Dipole Length

0

2

4

6

8

10

50 75 100 125 150 175 200

Design Frequency (MHz)D

ipo

le L

en

gth

(ft

)


T9A12 T9A12 (pg 153)(pg 153)

What is the approximate length, in inches, What is the approximate length, in inches, of a 6-meter 1/2 wavelength wire dipole antenna?of a 6-meter 1/2 wavelength wire dipole antenna?

A.A. 6 inches6 inches

B.B. 50 inches50 inches

C.C. 112 inches112 inchesD.D. 236 inches236 inches

Hint: On 6-meter band, ½ wavelength would be about 3 meters!Hint: On 6-meter band, ½ wavelength would be about 3 meters!

Closest answer is C.Closest answer is C.

3mLength 39 in.

1 m

117 in.


Beam AntennasBeam AntennasSend most of the radio energy in one direction Send most of the radio energy in one direction when transmitting.when transmitting.Listen primarily in one direction when receiving.Listen primarily in one direction when receiving.

“Dish”antenna

Quad antenna

Yagi antenna


T9A08 T9A08 (pg 154)(pg 154)

What type of antennas are the What type of antennas are the quad, Yagi, and dishquad, Yagi, and dish??A.A. Antennas invented after 1985Antennas invented after 1985

B.B. Loop antennasLoop antennas

C.C. Directional or Directional or beambeam antennas antennasD.D. Antennas that are not permitted Antennas that are not permitted

for amateur radio stationsfor amateur radio stations

Yagi antenna


T9A01 T9A01 (pg 154)(pg 154)

What is a beam antenna?What is a beam antenna?A.A. An antenna built from metal I-beamsAn antenna built from metal I-beams

B.B. An antenna that transmits and receives equally well An antenna that transmits and receives equally well in all directionsin all directions

C.C. An antenna that concentrates signals in An antenna that concentrates signals in one directionone direction

D.D. An antenna that reverses the phase of received An antenna that reverses the phase of received signalssignals


T0B05 T0B05 (pg 155)(pg 155)

What must be considered when erecting an What must be considered when erecting an antenna near an airport?antenna near an airport?

A.A. The maximum allowed height with regard The maximum allowed height with regard to nearby airportsto nearby airports

B.B. The possibility of interference to aircraft radiosThe possibility of interference to aircraft radios

C.C. The radiation angle of the signals it producesThe radiation angle of the signals it produces

D.D. The polarization of signal to be radiatedThe polarization of signal to be radiated


Coaxial Cable Coaxial Cable (pg 156-157)(pg 156-157)EasyEasy to use (like garden hose). to use (like garden hose). Characteristic impedance of Characteristic impedance of 50 ohms50 ohms. . Bad things can still happen, however.Bad things can still happen, however.– Ultraviolet damageUltraviolet damage

is slowed down by is slowed down by black outer sheath black outer sheath

– Moisture contaminationMoisture contamination – Resistance (losses) in Resistance (losses) in

cable turns radio cable turns radio energy to energy to heatheat


T9C12 T9C12 (pg 156)(pg 156)

Why is coaxial cable used more often than any Why is coaxial cable used more often than any other feed line for amateur radio antenna other feed line for amateur radio antenna systems?systems?

A.A. It is It is easy to useeasy to use and requires few special and requires few special installation considerationsinstallation considerations

B.B. It has less loss than any other type of feedlineIt has less loss than any other type of feedline

C.C. It can handle more power than any other type of It can handle more power than any other type of feedlinefeedline

D.D. It is less expensive than any other types of lineIt is less expensive than any other types of line


T9C11 T9C11 (pg 156)(pg 156)

What is the impedance of the most commonly What is the impedance of the most commonly used coaxial cable in typical amateur radio used coaxial cable in typical amateur radio installations?installations?A.A. 8 Ohms8 Ohms

B.B. 50 Ohms50 OhmsC.C. 600 Ohms600 Ohms

D.D. 12 Ohms12 Ohms


T9C10 T9C10 (pg 156)(pg 156)

Why is the outer sheath of most coaxial cables Why is the outer sheath of most coaxial cables black in color?black in color?A.A. It is the cheapest color to useIt is the cheapest color to use

B.B. To see nicks and cracks in the cableTo see nicks and cracks in the cable

C.C. Black cables have less lossBlack cables have less loss

D.D. Black provides protection against Black provides protection against ultraviolet damageultraviolet damage


T9C09 T9C09 (pg 156)(pg 156)

What can happen to older coaxial cables that are What can happen to older coaxial cables that are exposed to weather and sunlight for several exposed to weather and sunlight for several years?years?A.A. Nothing, weather and sunlight do not affect coaxial Nothing, weather and sunlight do not affect coaxial

cablecable

B.B. The cable can shrink and breakThe cable can shrink and break

C.C. LossesLosses can increase dramatically can increase dramaticallyD.D. It will short-circuitIt will short-circuit


T9C05 T9C05 (pg 156)(pg 156)

What happens to the power lost in a feed line?What happens to the power lost in a feed line?A.A. It increases the SWRIt increases the SWR

B.B. It comes back into your transmitter and could cause It comes back into your transmitter and could cause damagedamage

C.C. It is converted into heat by It is converted into heat by losseslosses in the line in the line

D.D. It can cause distortion of your signalIt can cause distortion of your signal


T9C07 T9C07 (pg 157)(pg 157)

What is the most common reason for failure of What is the most common reason for failure of coaxial cables?coaxial cables?

A.A. Moisture contaminationMoisture contaminationB.B. Gamma raysGamma rays

C.C. End of service lifeEnd of service life

D.D. OverloadingOverloading


SWR SWR (pg 157-158)(pg 157-158)

““SStanding tanding WWave ave RRatio” measures atio” measures how well how well transmitter is matched to the antennatransmitter is matched to the antenna (also (also known as the “load”).known as the “load”).

High SWR is bad—lots of power being reflected High SWR is bad—lots of power being reflected back into your radio can damage your radio, and back into your radio can damage your radio, and causes causes losseslosses in your feedline to the antenna, in your feedline to the antenna, meaning less signal gets out. meaning less signal gets out.

Perfect SWR is a Perfect SWR is a 1:11:1 (“1 to 1”) ratio. (“1 to 1”) ratio.

Poor SWR is Poor SWR is 2:12:1 (“2 to 1”) or greater. (“2 to 1”) or greater.


T9C01 T9C01 (pg 157)(pg 157)

What, in general terms, is standing wave ratio What, in general terms, is standing wave ratio (SWR)?(SWR)?

A.A. A measure of how well a load is matched A measure of how well a load is matched to a transmitterto a transmitter

B.B. The ratio of high to low impedance in a feed lineThe ratio of high to low impedance in a feed line

C.C. The transmitter efficiency ratioThe transmitter efficiency ratio

D.D. An indication of the quality of your station ground An indication of the quality of your station ground connectionconnection


T9C08 T9C08 (pg 157)(pg 157)

Why is it important to have a low SWR in an Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?antenna system that uses coaxial cable feedline?A.A. To reduce television interferenceTo reduce television interference

B.B. To allow the efficient transfer of power To allow the efficient transfer of power and reduce lossesand reduce losses

C.C. To prolong antenna lifeTo prolong antenna life

D.D. To keep your signal from changing polarizationTo keep your signal from changing polarization


T9C02 T9C02 (pg 157)(pg 157)

What reading on a SWR meter indicates a What reading on a SWR meter indicates a perfect impedance match between the antenna perfect impedance match between the antenna and the feed line?and the feed line?A.A. 2 to 12 to 1

B.B. 1 to 31 to 3

C.C. 1 to 11 to 1D.D. 10 to 110 to 1


T9C04 T9C04 (pg 158)(pg 158)

What is the SWR value where the protection What is the SWR value where the protection circuits in most solid-state transmitters begin to circuits in most solid-state transmitters begin to reduce transmitter power?reduce transmitter power?

A.A. 2 to 12 to 1B.B. 1 to 21 to 2

C.C. 6 to 16 to 1

D.D. 10 to 110 to 1


Measuring SWR Measuring SWR (pg 158-159)(pg 158-159)

SWR is a ratio of “forward SWR is a ratio of “forward power” to “reflected power.” power” to “reflected power.” So meters which measure So meters which measure those two those two directional quantities directional quantities can provide a can provide a system’s SWR. system’s SWR.

Erratic SWR readings are probably indicating a Erratic SWR readings are probably indicating a loose connectionloose connection. .

Use a “Use a “dummy loaddummy load” to purposely absorb all ” to purposely absorb all your signal when your signal when testing your stationtesting your station. .


T9C06 T9C06 (pg 158)(pg 158)

What instrument other than a SWR meter could What instrument other than a SWR meter could you use to determine if your feedline and you use to determine if your feedline and antenna are properly matched?antenna are properly matched?A.A. VoltmeterVoltmeter

B.B. OhmmeterOhmmeter

C.C. Iambic pentameterIambic pentameter

D.D. Directional wattmeterDirectional wattmeter


T9C03 T9C03 (pg 158)(pg 158)

What might be indicated by erratic changes in What might be indicated by erratic changes in SWR readings?SWR readings?A.A. The transmitter is being modulatedThe transmitter is being modulated

B.B. A loose connection in your antenna A loose connection in your antenna or feedlineor feedline

C.C. The transmitter is being over modulatedThe transmitter is being over modulated

D.D. Interference from other stations is distorting your Interference from other stations is distorting your signalsignal


T9A07 T9A07 (pg 159)(pg 159)

What is the primary purpose What is the primary purpose of a dummy load?of a dummy load?

A.A. It does not radiate interfering signals It does not radiate interfering signals when making testswhen making tests

B.B. It will prevent over-modulation of your transmitterIt will prevent over-modulation of your transmitter

C.C. It keeps you from making mistakes while on the airIt keeps you from making mistakes while on the air

D.D. It is used for close in work to prevent overloadsIt is used for close in work to prevent overloads


T3D08 T3D08 (pg 159)(pg 159)

What is the best way to reduce on the air What is the best way to reduce on the air interference when testing your transmitter?interference when testing your transmitter?A.A. Use a short indoor antenna when testingUse a short indoor antenna when testing

B.B. Use upper side band when testingUse upper side band when testing

C.C. Use a dummy load when Use a dummy load when testingtesting

D.D. Use a simplex frequency Use a simplex frequency instead of a repeater frequencyinstead of a repeater frequency


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