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Tuning
Tuning the
COM-20VA
20 Meter Vertical Antenna is straightforward and intuitive. If you use an
SWR meter or an analyzer at the base of the antenna you will get the most accurate readings in a
timely fashion. Since the bandwidth of the antenna is wide the adjustment parameters are relatively
broad and fine adjustment is not usually necessary.
Note: For the purposes of these instructions the term “resonance” or “resonant frequency” is
defined as the point of lowest SWR and may be used interchangeably.
To adjust the low SWR point in the 20 meter band, merely adjust the length of the top tubing
section in the normal manner, i.e., making it longer lowers the 20 meter resonant frequency and
shortening it raises the frequency. The top element section is made moveable by loosening the
element clamp and then sliding the upper element section of the antenna either closer to the base of
the antenna or farther away depending on whether you want to lower or raise the frequency of
resonance. Be sure to tighten the clamp after making an antenna length adjustment.
For 20 Meters
Frequency MHz
Approximate Overall Length
14.000
16 Feet, 8-1/2 inches
14.150
16 Feet, 6-1/2 inches
14.225
16 Feet, 5-3/8 inches
14.350
16 Feet, 3-5/8 inches
The approximate lengths shown in these tables should also be used when making resonant radials
for an elevated mount antenna (feedpoint is 3 feet or higher from ground level). For ground
mounted antennas, resonant radials are not required.
When used to make a higher frequency monoband vertical, telescope the extra lengths inside of
each other.
For 17 meters
Frequency MHz
Approximate Overall Length
18.068
12 Feet, 11-3/8 inches
18.110
12 Feet, 11 inches
18.130
12 Feet, 10-3/4 inches
18.168
12 Feet, 10-9/16 inches
For 15 meters
Frequency MHz
Approximate Overall Length
21.000
11 Feet, 1-11/16 inches
21.150
11 Feet, 3/4 inches
21.300
11 Feet
21.450
10 Feet, 10-13/16 inches
For 12 meters
Frequency MHz
Approximate Overall Length
24.890
9 Feet, 4-13/16 inches
24.940
9 Feet, 4-9/16 inches
24.990
9 Feet, 4-5/16 inches
