Tuning the 40m Add-On Dipole
Generally the 40m Add-On Dipole will resonate a little low and you may have to prune it to get resonance where you want it to be.
Resonance is tuned by adjusting the capacitive-loading wires on each end of the dipole.
NOTE: the wires on the reflector side of the dipole are a different length than the wires on the director side of the dipole.
When you shorten the 2 ends of each of these 2 loading wires, YOU MUST shorten all 4 ends by the exact same amount.
- Begin by measuring and recording the exact frequency on 40m where minimum SWR occurs. (Write it down; don't just memorize it.)
- Next, shorten each wire end by 10cm (4 inches).
- MEASURE AGAIN the frequency where minimum SWR occurs and record.
- Knowing how many kHz the frequency of SWRmin rises when shortening by 10cm, you can calculate how much more you must shorten to move SWRmin to your target frequency.
- CAUTION: ALWAYS move in small increments; do not cut all at once...that is a sure way to end up with the wires being too short.