FREE HAM Radio Extra Class Test Antennas and Feed Lines Questions and Answers Flashcards
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Read the first 6 FREE HAM Radio Extra Class Test Antennas and Feed Lines Questions and Answers flashcards as text
What is the effect of ground conductivity on the radiation pattern of a vertically polarized antenna?
Answer: Better ground conductivity improves low-angle radiation
Higher ground conductivity enhances low-angle radiation from vertical antennas, which is desirable for DX communications.
What is the characteristic impedance of standard window line (twin-lead) commonly used in amateur radio?
Answer: 300 ohms
Standard TV-type window line (twin-lead) has a characteristic impedance of 300 ohms.
Which of the following best describes the radiation pattern of a two-element Yagi antenna?
Answer: A cardioid pattern with maximum radiation toward the director
A two-element Yagi produces a cardioid-shaped pattern with the main lobe directed from the reflector toward the director.
What is the total loss in a feed line system if the matched-line loss is 2 dB and the SWR at the load is 3:1?
Answer: Greater than 2 dB due to additional SWR-related loss
When SWR is greater than 1:1, the total feed line loss exceeds the matched-line loss because reflected power traverses the lossy line multiple times.
What is the approximate gain of a five-element Yagi antenna over a dipole?
Answer: Approximately 10 dBd
A well-designed five-element Yagi typically provides about 10 dBd of gain over a reference dipole.
Why is it important to seal the end of coaxial cable exposed to weather?
Answer: To prevent moisture ingress that increases line loss
Moisture entering coaxial cable dramatically increases signal loss by altering the dielectric properties.