SUB-ELEMENT J

Question 1

Which of the following could cause a high standing wave ratio on a transmission line?
A. Excessive modulation.
B. An increase in output power.
C. A detuned antenna coupler.
D. Low power from the transmitter.

Answer 1

C

Question 2

Why is the value of the radiation resistance of an antenna important?
A. Knowing the radiation resistance makes it possible to match impedances for maximum power transfer.
B. Knowing the radiation resistance makes it possible to measure the near-field radiation density from transmitting antenna.
C. The value of the radiation resistance represents the front-to-side ratio of the antenna.
D. The value of the radiation resistance represents the front-to-back ratio of the antenna.

Answer 2

A

Question 3

A radio frequency device that allows RF energy to pass through in one direction with very little loss but absorbs RF power in the opposite direction is a:
A. Circulator.
B. Wave trap.
C. Multiplexer.
D. Isolator.

Answer 3

D

Question 4

What is an advantage of using a trap antenna?
A. It may be used for multiband operation.
B. It has high directivity in the high-frequency bands.
C. It has high gain.
D. It minimizes harmonic radiation.

Answer 4

A

Question 5

What is meant by the term radiation resistance of an antenna?
A. Losses in the antenna elements and feed line.
B. The specific impedance of the antenna.
C. The resistance in the trap coils to received signals.
D. An equivalent resistance that would dissipate the same amount of power as that radiated from an antenna.

Answer 5

D

Question 6

What is meant by the term antenna bandwidth?
A. Antenna length divided by the number of elements.
B. The frequency range over which an antenna can be expected to perform well.
C. The angle between the half-power radiation points.
D. The angle formed between two imaginary lines drawn through the ends of the elements.

Answer 6

B

Question 7

What is the current flowing through a 52 ohm line with an input of 1,872 watts?
A. 0.06 amps.
B. 6 amps.
C. 28.7 amps.
D. 144 amps.

Answer 7

B

Question 8

The voltage produced in a receiving antenna is:
A. Out of phase with the current if connected properly.
B. Out of phase with the current if cut to 1/3 wavelength.
C. Variable depending on the station’s SWR.
D. Always proportional to the received field strength.

Answer 8

D

Question 9

Which of the following represents the best standing wave ratio (SWR)?
A. 1:1.
B. 1:1.5.
C. 1:3.
D. 1:4.

Answer 9

A

Question 10

At the ends of a half-wave antenna, what values of current and voltage exist compared to the remainder of the antenna?
A. Equal voltage and current.
B. Minimum voltage and maximum current.
C. Maximum voltage and minimum current.
D. Minimum voltage and minimum current.

Answer 10

C

Question 11

An antenna radiates a primary signal of 500 watts output. If there is a 2nd harmonic output of 0.5 watt, what attenuation of the 2nd harmonic has occurred?
A. 10 dB.
B. 30 dB.
C. 40 dB.
D. 50 dB.

Answer 11

B

Question 12

There is an improper impedance match between a 30 watt transmitter and the antenna, with 5 watts reflected. How much power is actually radiated?
A. 35 watts.
B. 30 watts.
C. 25 watts.
D. 20 watts.

Answer 12

C

Question 13

A vertical 1/4 wave antenna receives signals:
A. In the microwave band.
B. In one vertical direction.
C. In one horizontal direction.
D. Equally from all horizontal directions.

Answer 13

D

Question 14

The resonant frequency of a Hertz antenna can be lowered by:
A. Lowering the frequency of the transmitter.
B. Placing an inductance in series with the antenna.
C. Placing a condenser in series with the antenna.
D. Placing a resistor in series with the antenna.

Answer 14

B

Question 15

An excited 1/2 wavelength antenna produces:
A. Residual fields.
B. An electro-magnetic field only.
C. Both electro-magnetic and electro-static fields.
D. An electro-flux field sometimes.

Answer 15

C

Question 16

To increase the resonant frequency of a 1/4 wavelength antenna:
A. Add a capacitor in series.
B. Lower capacitor value.
C. Cut antenna.
D. Add an inductor.

Answer 16

A

Question 17

What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?
A. It is increased.
B. It is decreased.
C. No change occurs.
D. It becomes flat.

Answer 17

B

Question 18

To lengthen an antenna electrically, add a:
A. Coil.
B. Resistor.
C. Battery.
D. Conduit.

Answer 18

A

Question 19

What is the meaning of the term velocity factor of a transmission line?
A. The ratio of the characteristic impedance of the line to the terminating impedance.
B. The velocity of the wave on the transmission line divided by the velocity of light in a vacuum.
C. The velocity of the wave on the transmission line multiplied by the velocity of light in a vacuum.
D. The index of shielding for coaxial cable.

Answer 19

B

Question 20

What determines the velocity factor in a transmission line?
A. The termination impedance.
B. The line length.
C. Dielectrics in the line.
D. The center conductor resistivity.

Answer 20

C

Question 21

Nitrogen is placed in transmission lines to:
A. Improve the “skin-effect” of microwaves.
B. Reduce arcing in the line.
C. Reduce the standing wave ratio of the line.
D. Prevent moisture from entering the line.

Answer 21

D

Question 22

A perfect (no loss) coaxial cable has 7 dB of reflected power when the input is 5 watts. What is the output of the transmission line?
A. 1 watt.
B. 1.25 watts.
C. 2.5 watts.
D. 5 watts.

Answer 22

A

Question 23

Referred to the fundamental frequency, a shorted stub line attached to the transmission line to absorb even harmonics could have a wavelength of:
A. 1.41 wavelength.
B. 1/2 wavelength.
C. 1/4 wavelength.
D. 1/6 wavelength.

Answer 23

C

Question 24

If a transmission line has a power loss of 6 dB per 100 feet, what is the power at the feed point to the antenna at the end of a 200 foot transmission line fed by a 100 watt transmitter?
A. 70 watts.
B. 50 watts.
C. 25 watts.
D. 6 watts.

Answer 24

D

Question 25

What is the effective radiated power of a repeater with 50 watts transmitter power output, 4 dB feedline loss, 3 dB duplexer and circulator loss, and 6 dB antenna gain?
A. 158 watts.
B. 39.7 watts.
C. 251 watts.
D. 69.9 watts.

Answer 25

B

Question 26

What is the effective radiated power of a repeater with 75 watts transmitter power output, 4 dB feedline loss, 3 dB duplexer and circulator loss, and 10 dB antenna gain?
A. 600 watts.
B. 75 watts.
C. 18.75 watts.
D. 150 watts.

Answer 26

D

Question 27

What is the effective radiated power of a repeater with 75 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 6 dB antenna gain?
A. 37.6 watts.
B. 237 watts.
C. 150 watts.
D. 23.7 watts.

Answer 27

A

Question 28

What is the effective radiated power of a repeater with 100 watts transmitter power output, 4 dB feedline loss, 3 dB duplexer and circulator loss, and 7 dB antenna gain?
A. 631 watts.
B. 400 watts.
C. 25 watts.
D. 100 watts.

Answer 28

D

Question 29

What is the effective radiated power of a repeater with 100 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 10 dB antenna gain?
A. 126 watts.
B. 800 watts.
C. 12.5 watts.
D. 1260 watts.

Answer 29

A

Question 30

What is the effective radiated power of a repeater with 50 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 7 dB antenna gain?
A. 300 watts.
B. 315 watts.
C. 31.5 watts.
D. 69.9 watts.

Answer 30

C