Technician Licensing Class Antennas feedlines T 9 A

Technician Licensing Class Antennas, feedlines T 9 A - T 9 B Valid July 1, 2014 Through June 30, 2018 1 Developed by Bob Bytheway, K 3 DIO, and slightly modified by SPARC

T 9 A • The beam antenna concentrates signals in one direction. T 9 A 01 2

T 9 A • Regarding vertical antennas, the electric field is perpendicular to the earth. T 9 A 02 3

Antennas 4

T 9 A • A simple dipole mounted so that the conductor is parallel to the Earth’s surface is a horizontally polarized antenna. T 9 A 03 • A disadvantage of the “rubber duck” antenna supplied with most handheld transceivers does not transmit or receive as effectively as a full sized antenna. T 9 A 04 5

T 9 A • To change a dipole antenna to make it resonant on a higher frequency, shorten it. • The quad, Yagi, and dish antennas are directional antennas. T 9 A 05 T 9 A 06 quad Yagi dish 6

T 9 A • Signals can be significantly weaker when using a “rubber duck” antenna inside versus outside your car. • The approximate length, in inches, of a quarter-wave vertical antenna for 146 MHz is 19”. T 9 A 08 T 9 A 07 19” 7

T 9 A • The approximate length of a 6 -meter, halfwave wire dipole antenna is 112. 3 inches. T 9 A 09 • The direction of radiation is strongest from a half-wave dipole antenna in free space broadside to the antenna. 8 T 9 A 10

T 9 A • The increase in signal strength in a specified direction when compared to a reference antenna is referred to as the gain of an antenna. T 9 A 11 9

T 9 A • A properly mounted 5/8 wavelength antenna for VHF or UHF mobile service offers a lower angle of radiation and more gain than a ¼ wavelength antenna and usually provides improved coverage. T 9 A 12 10

T 9 A • VHF and UHF mobile antennas are often mounted in the center of the vehicle roof which normally provides the most uniform radiation pattern. • A type of loading when referring to an antenna is when an inductor is inserted in the radiating portion of the antenna to make it electrically longer and is called a loading coil. T 9 A 13 T 9 A 14 11

T 9 B • It is important to have a low SWR in an antenna system that uses coaxial cable feed line to allow the efficient transfer of power and reduce losses. T 9 B 01 12

T 9 B • The most commonly used coaxial cable in typical amateur radio installations is 50 ohm impedance. T 9 B 02 13

T 9 B • Coaxial cable is used more often than any other feed line for amateur radio antenna systems due to the ease of use and it requires few special installation considerations. T 9 B 03 14

T 9 B • An antenna tuner matches the antenna system impedance to the transceiver’s output impedance. T 9 B 04 Fully auto tuner Icom AH 4 Manual tuner Palstar AT 5 K 15

T 9 B • As the frequency of a signal passing through coaxial cable is increased the loss increases. • Type N connectors are most suitable for frequencies above 400 MHz. T 9 B 05 T 9 B 06 • PL-259 type coax connectors are commonly used at HF frequencies. T 9 B 07 16

T 9 B • Coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feed line loss. • Erratic changes in SWR readings might be caused by a loose connection in an antenna or a feed line. T 9 B 08 T 9 B 09 Make sure all your coaxial connections are tight to help minimize interference and erratic conditions. 17

T 9 B • The electrical difference existing between the smaller RG -58 and larger RG-8 coaxial cables it that the RG-8 has less loss at a give frequency. T 9 B 10 RG-8 RG-58 • The lowest loss at VHF and UHF type of feed line is air 18 insulated hardline coax. T 9 B 11

Element 2 Technician Class Question Pool T 9 A–T 9 B Valid July 1, 2014 Through June 30, 2018 19

T 9 A 01 What is a beam antenna? A. An antenna built from aluminum Ibeams B. An omnidirectional antenna invented by Clarence Beam C. An antenna that concentrates signals in one direction D. An antenna that reverses the phase of received signals 20

T 9 A 02 Which of the following is true regarding vertical antennas? A. The magnetic field is perpendicular to the Earth B. The electric field is perpendicular to the Earth C. The phase is inverted D. The phase is reversed 21

T 9 A 03 Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface? A. B. C. D. A ground wave antenna A horizontally polarized antenna A rhombic antenna A vertically polarized antenna 22

T 9 A 04 What is a disadvantage of the "rubber duck" antenna supplied with most handheld radio transceivers? A. It does not transmit or receive as effectively as a full-sized antenna B. It transmits a circularly polarized signal C. If the rubber end cap is lost it will unravel very quickly D. All of these choices are correct 23

T 9 A 05 How would you change a dipole antenna to make it resonant on a higher frequency? A. B. C. D. Lengthen it Insert coils in series with radiating wires Shorten it Add capacity hats to the ends of the radiating wires 24

T 9 A 06 What type of antennas are the quad, Yagi, and dish? A. B. C. D. Non-resonant antennas Loop antennas Directional antennas Isotropic antennas 25

T 9 A 07 What is a good reason not to use a "rubber duck" antenna inside your car? A. Signals can be significantly weaker than when it is outside of the vehicle B. It might cause your radio to overheat C. The SWR might decrease, decreasing the signal strength D. All of these choices are correct 26

T 9 A 08 What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? A. B. C. D. 112 50 19 12 27

T 9 A 09 What is the approximate length, in inches, of a 6 meter 1/2 -wavelength wire dipole antenna? A. B. C. D. 6 50 112 236 28

T 9 A 10 In which direction is the radiation strongest from a half-wave dipole A. B. C. D. antenna in free space? Equally in all directions Off the ends of the antenna Broadside to the antenna In the direction of the feedline 29

T 9 A 11 What is meant by the gain of an antenna? A. The additional power that is added to the transmitter power B. The additional power that is lost in the antenna when transmitting on a higher frequency C. The increase in signal strength in a specified direction when compared to a reference antenna D. The increase in impedance on receive or transmit compared to a reference antenna 30

T 9 A 12 What is a reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service? A. It offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage B. It features a very high angle of radiation and is better for communicating via a repeater C. The 5/8 wavelength antenna completely eliminates distortion caused by reflected signals D. The 5/8 wavelength antenna offers a 10 -times power gain over a 1/4 wavelength design 31

T 9 A 13 Why are VHF or UHF mobile antennas often mounted in the center of the vehicle roof? A. Roof mounts have the lowest possible SWR of any mounting configuration B. Only roof mounting can guarantee a vertically polarized signal C. A roof mounted antenna normally provides the most uniform radiation pattern D. Roof mounted antennas are always the easiest to install 32

T 9 A 14 Which of the following terms describes a type of loading when referring to an antenna? A. Inserting an inductor in the radiating portion of the antenna to make it electrically longer B. Inserting a resistor in the radiating portion of the antenna to make it resonant C. Installing a spring at the base of the antenna to absorb the effects of collisions with other objects D. Making the antenna heavier so it will resist wind effects when in motion 33

T 9 B 01 Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line? A. To reduce television interference B. To allow the efficient transfer of power and reduce losses C. To prolong antenna life D. All of these choices are correct 34

T 9 B 02 What is the impedance of the most commonly used coaxial cable in typical amateur radio installations? A. B. C. D. 8 ohms 50 ohms 600 ohms 12 ohms 35

T 9 B 03 Why is coaxial cable used more often than any other feedline 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 feedline 36

T 9 B 04 What does an antenna tuner do? A. It matches the antenna system impedance to the transceiver's output impedance B. It helps a receiver automatically tune in weak stations C. It allows an antenna to be used on both transmit and receive D. It automatically selects the proper antenna for the frequency band being used 37

T 9 B 05 What generally happens as the frequency of a signal passing through coaxial cable is increased? A. B. C. D. The apparent SWR increases The reflected power increases The characteristic impedance increases The loss increases 38

T 9 B 06 Which of the following connectors is most suitable for frequencies above 400 MHz? A. B. C. D. A UHF (PL-259/SO-239) connector A Type N connector An RS-213 connector A DB-25 connector 39

T 9 B 07 Which of the following is true of PL-259 type coax connectors? A. B. C. D. They are preferred for microwave operation They are water tight The are commonly used at HF frequencies They are a bayonet type connector 40

T 9 B 08 Why should coax connectors exposed to the weather be sealed against water intrusion? A. B. C. D. To prevent an increase in feedline loss To prevent interference to telephones To keep the jacket from becoming loose All of these choices are correct 41

T 9 B 09 What might cause erratic changes in SWR readings? A. The transmitter is being modulated B. A loose connection in an antenna or a feedline C. The transmitter is being over-modulated D. Interference from other stations is distorting your signal 42

T 9 B 10 What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables? A. There is no significant difference between the two types B. RG-58 cable has less loss at a given frequency C. RG-8 cable has less loss at a given frequency D. RG-58 cable can handle higher power levels 43

T 9 B 11 Which of the following types of feedline has the lowest loss at VHF and UHF? A. B. C. D. 50 -ohm flexible coax Multi-conductor unbalanced cable Air-insulated hard line 75 -ohm flexible coax 44