Frequency and SWR Adjustment
The antenna is tuned to the operating frequency by adjusting the tap on the loading coil and the
length of the counterpoise wire. The excess counterpoise wire should be wrapped in a small coil
3-4 inches in diameter. The SWR is checked using a transmitter and SWR meter but will be
much easier using an analyzer such as the MFJ-259/269 SWR Analyzer. Initial tuning will
require some time. A permanent marker can be used to place marks on the coil to reduce the
amount of time required for future tuning.
Before tuning check the following:
q Coax Connections
q Counterpoise Connections and Length
q Whip Connection and Length
q The tap is only touching one coil turn
[ ] 1. Begin by placing the tap on turn 0 (Figure 2) which will short the entire coil. The tap
should only be in contact with one coil at a time.
Figure 2
[ ] 2. The counterpoise wire should be less than 1/4 wavelength of the desired frequency
[ 468 / frequency (MHz) ]. This length may need to be increased or decreased according
to height above ground level.
[ ] 3. With the tap on turn 0 and the counterpoise just under 8 feet, the resonance point should
be approximately 30 MHz. If this is not true lower the tap on the coil to lower the
frequency or shorten the whip to raise the frequency. Table 1 gives approximate tap
points for each of the HF bands with the counterpoise at ground level.
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