Technician Licensing Class “T9” Presented by the Plano Texas Stake Plano, Texas February 3, 2007

Technician Licensing Class“T9”

Presented by thePlano Texas Stake

Plano, Texas

February 3, 2007

2

Amateur Radio Technician ClassElement 2

• ELEMENT 2 SUBELEMENTS

• T1 - FCC Rules, station license responsibilities• T2 - Control operator duties• T3 - Operating practices• T4 - Radio and electronic fundamentals• T5 - Station setup and operation• T6 - Communications modes and methods• T7 - Special operations• T8 - Emergency and Public Service Communications• T9 - Radio waves, propagation, and antennas• T0 - Electrical and RF Safety

3

Radio waves, propagation, and antennas T9A

• A vertical antenna is an antenna that consists of a single element mounted perpendicular to the Earth's surface.

• A horizontal antenna is a simple dipole mounted so the elements are parallel to the Earth's surface.

Antenna types – vertical, horizontal

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Concept of gain• The advantage of 5/8 wavelength over 1/4

wavelength vertical antennas is their radiation pattern concentrates energy at lower angles.

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Concept of gain (cont) • A beam antenna is an antenna that

concentrates signals in one direction.

• The quad, Yagi, and dish are all types of directional or beam antennas.

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Common portable and mobile antennas, losses with short antennas• A disadvantage of the "rubber duck" antenna

supplied with most hand held radio transceivers is it does not transmit or receive as effectively as a full sized antenna.

• A good reason not to use a "rubber duck" antenna inside your car is that signals can be 10 to 20 times weaker than when you are outside of the vehicle.

• A magnet mount vertical antenna is one type of antenna that offers good efficiency when operating mobile and can be easily installed or removed.

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Relationships between antenna length and frequency

• The physical size of half-wave dipole antenna becomes shorter as the operating frequency increases.

• The approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz is 19 inches. [Remember the relationship between wavelength and frequency.]

• The approximate length, in inches, of a 6-meter half- wavelength wire dipole antenna is 112 inches. [Remember the relationship between wavelength and frequency.]

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The ¼ & ½ Wave Vertical

Length of vertical in feet =

234 f (MHz)

¼ Wave 19”

¼ Wave Radials

Feed Point

½ Wave 112”Feed Point

½ Wave Radials

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Dummy loads• The primary purpose of a

dummy load is it does not radiate interfering signals when making tests.

[Actually, it may radiate but the signal level radiated is usually well attenuated.]

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Radio waves, propagation, and antennas T9B

Propagation

• VHF/UHF signals not normally heard over long distances due to VHF and UHF signals usually not being reflected by the ionosphere.

• When we hear a VHF signal from long distances a possible cause is sporadic E reflection from a layer in the ionosphere.

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Ionospheric Layers

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Critical Angle

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Fading, Multipath distortion

• Picket fencing is a term commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting.

• If a station reports that your signals were strong just a moment ago, but now they are weak or distorted, try moving a few feet, random reflections may be causing multi-path distortion.

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Fading, Multipath distortion (cont)

• The most likely cause of sudden bursts of tones or fragments of different conversations that interfere with VHF or UHF signals is when strong signals are overloading the receiver and causing undesired signals to be heard.

Reflections• A way to reach a distant repeater if buildings

or obstructions are blocking the direct line of sight path is to try using a directional antenna to find a path that reflects signals to the repeater.

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Radio horizon, Terrain blocking

• The radio horizon is the point where radio signals between two points are blocked by the curvature of the Earth.

• VHF and UHF Radio signals usually travel about a third farther than the visual line of sight distance between 2 stations because the Earth seems less curved to radio waves than to light.

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Radio horizon distance

• The distance, D1 to the radio horizon for the transmitter is 1.415 times the square root of h1 (feet).

• The theoretical maximum line-of-sight distance between two

elevated points, presumably the transmitter (h1) and the receiver (h2), is the sum of the two distances to the radio horizon (D1 + D2).

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Wavelength vs. penetration

• UHF signals often work better inside of buildings than VHF signals since the shorter wavelength of UHF signals allows them to more easily penetrate urban areas and buildings.

• [This means 440 mHz (70 centimeters) signals, being UHF have a better chance of penetration inside buildings than 144 mHz ( 2-meters) signals do.]

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Antenna orientation

• If the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization signals could be as much as 100 times weaker.

• A good thing to remember when using your hand-held VHF or UHF radio to reach a distant repeater is to keep the antenna as close to vertical as you can.

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Radio waves, propagation, and antennas T9C

Feedline types, Losses vs. frequency, matching and power transfer

• Coaxial cable is used more often than any other feed line for amateur radio antenna systems because it is easy to use and requires few special installation considerations.

• The characteristic impedance of the most commonly used coaxial cable in typical amateur radio installations is 50 Ohms.

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Coax Cable Signal Loss (Attenuation) in dB per 100ft

Loss RG-174 RG-58 RG-8X RG-213 RG-6 RG-11 9913 LMR-400

1MHz 1.9dB 0.4dB 0.5dB 0.2dB 0.2dB 0.2dB 0.2dB 0.3dB








1GHz 32.0dB 21.5dB 13.5dB 8.3dB 6.1dB 5.6dB 4.5dB 4.1dB

Imped 50ohm 50ohm 50ohm 50ohm 75ohm 75ohm 50ohm 50ohm

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SWR concepts

• In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmitter.

• It is important to have a low SWR in an antenna system that uses coaxial cable feedline to allow the efficient transfer of power and reduce losses.

• A reading on a SWR meter of 1 to 1 (1:1) indicates a perfect impedance match between the antenna and the feed line.

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Measuring SWR• A Directional wattmeter could be used to determine if

your feedline and antenna are properly matched.

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SWR concepts (cont)

• A loose connection in your antenna or feedline might be indicated by erratic changes in SWR readings.

• The SWR value, 2 to 1 (2:1) is where the protection circuits in most solid-state transmitters begin to reduce transmitter power.

• The power lost in a feed line is converted into heat by losses in the line.

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The Antenna TunerThe Antenna Tuner

““Antenna Tuners” do not really tune antennas.Antenna Tuners” do not really tune antennas.They provide an impedance match betweenThey provide an impedance match between

the transmitter and antenna system.the transmitter and antenna system.

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Weather protection• Losses can increase dramatically in older

coaxial cables that are exposed to weather and sunlight for several years.

• The outer sheath of most coaxial cables is black in color because black provides protection against ultraviolet damage.

Feedline failure modes• Moisture contamination is the most common

reason for failure of coaxial cables.

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Take Aways

• Vertical antenna perpendicular to earth

• Horizontal antenna parallel to earth

• Beams concentrate signals in one direction

• Quad, Yagi, and Dish are directional antennas

• Rubber duck antenna not as effective as full sized

• 10-20 times reduction in signal strength inside car with rubber duck versus outside antenna

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Take Aways (cont)

• Mag mount antenna good efficiency in mobile

• Lower angle of radiation … 5/8 has more gain than 1/4 wavelength

• Half-wave dipole shorter when frequency increases

• 146 mHz quarter-wave … 19 inches• Half-wave 6-meter dipole 112 inches• Dummy load … no interferring radiation

when testing

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Take Aways (cont)

• VHF/UHF signals not reflected by ionsphere … not good for long distances

• Hear VHF long distance … sporadic E reflection in ionsphere

• Rapid fluttering from mobiles stations … picket fencing is term

• You were strong, now weak … move a few feet• Strong overloading receiver … sudden bursts of

tones or fragments of conversations• Directional antenna to reach distant repeater if

buildings or obstructions block direct LOS

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Take Aways (cont)

• Coax cable most used feed line due to ease of use and few special installation considerations

• Coax is commonly 50 ohms• SWR … load matching to a transmitter• For efficient transfer of power and reduction

of loss, low SWR important• One to one … 1:1 … perfect match• Directional wattmeter used for feedline and

antenna matching

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Take Aways (cont)

• Loose connections can cause erratic SWR readings

• SWR of 2:1 where some protection circuits reduce power

• Power lost in feed line converts to heat by losses in the line

• Losses increase with older coax exposed to weather

• Black cover offers protection against untraviolet damage

• Moisture is most common cause of failure for coax

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Take Aways (cont)

• Two points blocked by curvature of earth is radio horizon

• VHF/UHF signals travel about a third farther than visual LOS … earth less curved to radio waves than light

• UHF signals penetrate urban areas/building … shorter wavelength

• Cross polarization weakens signals about 100 times

• Keep HT VHF/UHF antenna vertical

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Element 2 Technician Class Question Pool

T9

Valid July 1, 2006

Through

June 30, 2010

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T9A01 What is a beam antenna?

A. An antenna built from metal I-beamsB. An antenna that transmits and

receives equally well in all directionsC. An antenna that concentrates signals

in one direction D. An antenna that reverses the phase

of received signals

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T9A02 What is an antenna that consists of a single element mounted perpendicular to the Earth's surface?

A. A conical monopoleB. A horizontal antennaC. A vertical antennaD. A traveling wave antenna

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T9A03 What type of antenna is a simple dipole mounted so the elements are parallel to the Earth's surface?

A. A ground wave antennaB. A horizontal antennaC. A rhombic antennaD. A vertical antenna

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T9A04 What is a disadvantage of the "rubber duck" antenna supplied with most hand held radio transceivers?

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

B. It is much more expensive than a standard antenna

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

D. It transmits a circular polarized signal

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T9A05 How does the physical size of half-wave dipole antenna change with operating frequency?

A. It becomes longer as the frequency increases

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

C. It becomes shorter as the frequency increases

D. It becomes shorter as the frequency deceases

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T9A06 What is the advantage of 5/8 wavelength over 1/4 wavelength vertical antennas?

A. They are easier to match to the feed line than other types

B. Their radiation pattern concentrates energy at lower angles

C. They pick up less noiseD. Their radiation pattern concentrates

energy at higher angles

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T9A07 What is the primary purpose of a dummy load?

A. It does not radiate interfering signals when making tests

B. It will prevent over-modulation of your transmitter

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

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

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T9A08 What type of antennas are the quad, Yagi, and dish?

A. Antennas invented after 1985B. Loop antennasC. Directional or beam antennasD. Antennas that are not permitted for

amateur radio stations

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T9A09 What is one type of antenna that offers good efficiency when operating mobile and can be easily installed or removed?

A. A microwave antennaB. A quad antennaC. A traveling wave antennaD. A magnet mount vertical antenna

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T9A10 What is a good reason not to use a

"rubber duck" antenna inside your car?

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

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

C. You might cause a fire in the vehicle upholstery

D. The SWR might increase

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T9A11 What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?

A. 112 inchesB. 50 inchesC. 19 inchesD. 12 inches

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T9A12 What is the approximate length, in inches, of a 6-meter 1/2 wavelength wire dipole antenna?

A. 6 inchesB. 50 inchesC. 112 inchesD. 236 inches

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T9B01 Why are VHF/UHF signals not normally

heard over long distances?

A. They are too weak to go very far B. FCC regulations prohibit them from

going more than 50 milesC. VHF and UHF signals are usually not

reflected by the ionosphere D. They collide with trees and shrubbery

and fade out

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T9B02 What might be happening when we

hear a VHF signal from long distances?

A. Signals are being reflected from outer space

B. Someone is playing a recording to usC. Signals are being reflected by

lightning storms in our areaD. A possible cause is sporadic E

reflection from a layer in the ionosphere

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T9B03 What is the most likely cause of sudden bursts of tones or fragments of different conversations that interfere with VHF or UHF signals?

A. The batteries in your transceiver are failing B. Strong signals are overloading the receiver

and causing undesired signals to be heardC. The receiver is picking up low orbit

satellitesD. A nearby broadcast station is having

transmitter problems

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T9B04 What is the radio horizon?

A. The point where radio signals between two points are blocked by the curvature of the Earth

B. The distance from the ground to a horizontally mounted antenna

C. The farthest point you can see when standing at the base of your antenna tower

D. The shortest distance between two points on the Earth's surface

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T9B05 What should you do if a station reports that your signals were strong just a moment ago, but now they are weak or distorted?

A. Change the batteries in your radio to a different type

B. Speak more slowly so he can understand your better

C. Ask the other operator to adjust his squelch control

D. Try moving a few feet, random reflections may be causing multi-path distortion.

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T9B06 Why do UHF signals often work better

inside of buildings than VHF signals?

A. VHF signals lose power faster over distanceB. The shorter wavelength of UHF signals

allows them to more easily penetrate urban areas and buildings

C. This is incorrect; VHF works better than UHF inside buildings

D. UHF antennas are more efficient than VHF antennas

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T9B07 What is a good thing to remember when using your hand-held VHF or UHF radio to reach a distant repeater?

A. Speak as loudly as possible to help your signal go farther

B. Keep your transmissions short to conserve battery power

C. Keep the antenna as close to vertical as you can

D. Turn off the CTCSS tone

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T9B08 What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?

A. The modulation sidebands might become inverted

B. Signals could be as much as 100 times weaker

C. Signals have an echo effect on voicesD. Nothing significant will happen

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T9B09 What might be a way to reach a distant repeater if buildings or obstructions are

blocking the direct line of sight path?

A. Change from vertical to horizontal polarization

B. Try using a directional antenna to find a path that reflects signals to the repeater

C. Ask the repeater owners to repair their receiver

D. Transmit on the repeater output frequency

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T9B10 What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?

A. Flip-floppingB. Picket fencing C. Frequency shiftingD. Pulsing

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T9B11 Why do VHF and UHF Radio signals usually travel about a third farther than the visual line of sight distance between 2 stations?

A. Radio signals move somewhat faster than the speed of light and travel farther in the same amount of time

B. Radio waves are not blocked by dust particles

C. The Earth seems less curved to radio waves than to light

D. Radio waves are blocked by dust particles

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T9C01 What, in general terms, is standing wave ratio (SWR)?

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

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

C. The transmitter efficiency ratioD. An indication of the quality of your

station ground connection

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T9C02 What reading on a SWR meter indicates a perfect impedance match between the antenna and the feed line?

A. 2 to 1B. 1 to 3C. 1 to 1D. 10 to 1

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T9C03 What might be indicated by erratic changes in SWR readings?

A. The transmitter is being modulated B. A loose connection in your antenna

or feedlineC. The transmitter is being over

modulated D. Interference from other stations is

distorting your signal

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T9C04 What is the SWR value where the protection circuits in most solid-state transmitters begin to reduce transmitter power?

A. 2 to 1B. 1 to 2C. 6 to 1D. 10 to 1

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T9C05 What happens to the power lost in a feed line?

A. It increases the SWRB. It comes back into your transmitter

and could cause damage C. It is converted into heat by losses in

the line D. It can cause distortion of your signal

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T9C06 What instrument other than a SWR meter could you use to determine if your feedline and antenna are properly matched?

A. VoltmeterB. OhmmeterC. Iambic PentameterD. Directional wattmeter

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T9C07 What is the most common reason for failure of coaxial cables?

A. Moisture contamination B. Gamma raysC. End of service lifeD. Overloading

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T9C08 Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?

A. To reduce television interference B. To allow the efficient transfer of

power and reduce lossesC. To prolong antenna life D. To keep your signal from changing

polarization

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T9C09 What can happen to older coaxial cables that are exposed to weather and sunlight

for several years?

A. Nothing, weather and sunlight do not affect coaxial cable

B. The cable can shrink and break C. Losses can increase dramaticallyD. It will short-circuit

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T9C10 Why is the outer sheath of most coaxial cables black in color?

A. It is the cheapest color to use B. To see nicks and cracks in the cable C. Black cables have less loss D. Black provides protection against

ultraviolet damage

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T9C11 What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?

A. 8 OhmsB. 50 OhmsC. 600 OhmsD. 12 Ohms

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T9C12 Why is coaxial cable used more often than any other feed line for amateur radio antenna systems?

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

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

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

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

Documents

Technician Licensing Class “T9” Presented by the Plano Texas Stake Plano, Texas February 3, 2007