FCC Technician Class Exam Study Guide - 2014-2018/Subelement T9 Group B

Feed lines: types of feed lines; attenuation vs. frequency; SWR concepts; matching; weather protection; choosing RF connectors and feed lines

Question 1

 * 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

The correct answer is B.

Question 2

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

The correct answer is B.

Question 3

 * 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 feed line
 * C. It can handle more power than any other type of feed line
 * D. It is less expensive than any other types of feed line

The correct answer is A.

Question 4

 * 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

The correct answer is A.

Question 5

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

The correct answer is D.

Question 6

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

The correct answer is B.

Question 7

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

The correct answer is C.

Question 8

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

The correct answer is A.

Question 9

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

The correct answer is B.

Question 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

The correct answer is C.

Question 11

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

The correct answer is C.