> This is not encouraging news for those of us with towers already ground
> and are either shunt fed or cage fed.
Shunt fed towers can be detuned, or taken out of the picture by phasing a
small sample of signals into the RX antenna.
> I could try a motor driven inductor or capacitor (small) just to see while
> QSX on various RX antennas. Is the required reactance likely to be
> inductive or capacitive reacatance?
It depends on what is on the tower, the shunt system, and the grounding.
It can be anything from open circuit on the drop wire to fairly high
reactance.
There are too many variables to guess. Outside of measurements, you could
model the tower and add a distant vertical 300-500 feet away that is excited
as a source. Then find a detuning value for minimum pattern distortion and
current in the tower.
You'll see considerable pattern distortion on 160 meters from a resonant
structure even 500 feet or further away, so obviously there can be
considerable interaction to receive antennas even at a fairly large
distance.
My small vertical reversible Europe array, with each cell 70 foot spacing
between two verticals for endfire, and 350 foot broadside spacing, has one
endfire cell about 250 feet from my transmitting 4 square. When it looks
back into the four square, while watching W1AW, I can change the level of
W1AW 20 dB or more by playing with the TX antenna termination in the house.
A resistor is never good, but shorts and opens or reactances can be.
Some of my RX antenna to TX antenna coupling data is at the bottom of this
page:
http://www.w8ji.com/antenna_coupling.htm
Having two antennas in the nulls of each other is worth a whole lot more
than distance.
73 Tom
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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