Unfortunately, the Cushcraft 40 will detune the TH7DXX on 15m at any
spacing you can manage on the
There have been numerous instances locally of "pulling" any 15 meter
antenna's tuning by co-masted
Cushcraft 40's. It also modifies the pattern at 15m.
This happens because without modification a 40 antenna is also resonant at
three times the
frequency. Some 40m beams are specifically designed to be placed in
proximity to tribanders, etc.
The Force 12 x40N antennas are linearly loaded, and their secondary
resonance is around 18 MHz
instead of 21. Also their Delta x40 antennas were specifically designed to
resonance in 21 MHz band.
There may be other commercial 40m antennas that are non-resonant at 21
MHz, but I don't know of any.
| I will put a Hy-Gain TH7DXX and a Cushcraft 2 elem. 40 mts Yagi in the
| same mast on top of a tower.
| Will apreciate any recomendation about will antenna must be at top and
| the space between both antennas for not interaction.
| Thanks in advance