HAM Antennas and Feed Lines 3

Question 1

What is the characteristic impedance of open-wire (ladder) line typically used with balanced antenna tuners?

Accepted Answer

300 to 600 ohms

Answer

50 ohms

Answer

75 ohms

Answer

1000 ohms

Question 2

What is the effect of adding a director element to a Yagi antenna in front of the driven element?

Accepted Answer

It increases the front-to-back ratio and forward gain

Answer

It broadens the antenna bandwidth

Answer

It raises the feed point impedance

Answer

It rotates the polarization 90 degrees

Question 3

What is a loading coil used for in a shortened mobile HF antenna?

Accepted Answer

To add inductance and resonant the electrically short antenna

Answer

To increase the antenna's bandwidth

Answer

To lower the antenna's feed point impedance to 50 ohms

Answer

To protect the antenna from lightning

Question 4

What is the input impedance of a quarter-wave matching section (Q-section) used to transform a 200-ohm antenna to 50 ohms?

Accepted Answer

100 ohms

Answer

50 ohms

Answer

150 ohms

Answer

200 ohms

Question 5

What is the approximate gain of a three-element Yagi antenna relative to a dipole?

Accepted Answer

5 dBd

Answer

3 dBd

Answer

7 dBd

Answer

10 dBd

Question 6

Which transmission line type has the lowest loss per unit length at VHF frequencies?

Accepted Answer

Open-wire ladder line

Answer

RG-58 coaxial cable

Answer

RG-8 coaxial cable

Answer

Hardline coaxial cable

Question 7

What is a collinear antenna array designed to achieve?

Accepted Answer

High directivity toward the horizon by stacking vertical elements in phase

Answer

High front-to-back ratio for directional communication

Answer

Circular polarization for satellite work

Answer

Very low angle radiation for NVIS propagation