G9A: Antenna feedlines: characteristic impedance, and attenuation; SWR calculation, measurement and effects; matching networks
G9A01:
Which of the following factors help determine the characteristic impedance of a parallel conductor antenna feedline?
The distance between the centers of the conductors and the radius of the conductors
The distance between the centers of the conductors and the length of the line
The radius of the conductors and the frequency of the signal
The frequency of the signal and the length of the line
G9A02:
What is the typical characteristic impedance of coaxial cables used for antenna feedlines at amateur stations?
50 and 75 ohms
25 and 30 ohms
80 and 100 ohms
500 and 750 ohms
G9A03:
What is the characteristic impedance of flat ribbon TV type twin lead?
300 ohms
50 ohms
75 ohms
100 ohms
G9A04:
What is a common reason for the occurrence of reflected power at the point where a feedline connects to an antenna?
A difference between feedline impedance and antenna feed point impedance
Operating an antenna at its resonant frequency
Using more transmitter power than the antenna can handle
Feeding the antenna with unbalanced feedline
G9A05:
What must be done to prevent standing waves on an antenna feedline?
The antenna feed point impedance must be matched to the characteristic impedance of the feedline
The antenna feed point must be at DC ground potential
The feedline must be cut to an odd number of electrical quarter wavelengths long
The feedline must be cut to an even number of physical half wavelengths long
G9A06:
Which of the following is a reason for using an inductively coupled matching network between the transmitter and parallel conductor feed line feeding an antenna?
To match the unbalanced transmitter output to the balanced parallel conductor feedline
To increase the radiation resistance
To reduce spurious emissions
To reduce the feed-point impedance of the antenna
G9A07:
How does the attenuation of coaxial cable change as the frequency of the signal it is carrying increases?
It increases
It is independent of frequency
It decreases
It reaches a maximum at approximately 18 MHz
G9A08:
In what values are RF feed line losses usually expressed?
dB per 100 ft
ohms per 1000 ft
dB per 1000 ft
ohms per 100 ft
G9A09:
What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 200-ohm impedance?
4:1
1:4
2:1
1:2
G9A10:
What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 10-ohm impedance?
5:1
2:1
50:1
1:5
G9A11:
What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 50-ohm impedance?
1:1
2:1
50:50
0:0
G9A12:
What would be the SWR if you feed a vertical antenna that has a 25-ohm feed-point impedance with 50-ohm coaxial cable?
2:1
2.5:1
1.25:1
You cannot determine SWR from impedance values
G9A13:
What would be the SWR if you feed a folded dipole antenna that has a 300-ohm feed-point impedance with 50-ohm coaxial cable?
6:1
1.5:1
3:1
You cannot determine SWR from impedance values
G9A14:
If the SWR on an antenna feedline is 5 to 1, and a matching network at the transmitter end of the feedline is adjusted to 1 to 1 SWR, what is the resulting SWR on the feedline?
5 to 1
1 to 1
Between 1 to 1 and 5 to 1 depending on the characteristic impedance of the line
Between 1 to 1 and 5 to 1 depending on the reflected power at the transmitter
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