> Gary Nichols KD9SV wrote:
>> Has anyone on this reflector been able to detune a grounded tower using
>> one or two drop wires instead of the Usual three.
> Greg, ZL3IX replied:
> With the tower only 70 ft high, you should get enough detuning simply by
> disconnecting the coax from the shunt feed with a relay, when on Rx.
_____
I have a nearly identical situation to Gary -- 72' tapered self-supporter,
but currently there are no antennas installed, and very little re-radiation.
However, this tower will approach resonance at 160M when a 10 ft. mast,
large tribander and 40M beam are installed. I will need to detune it, since
it is only 150 ft. from the 160M vertical.
My tower tapers from 36" to 11" -- I expect one drop wire to make a large
improvement, probably needing a second drop wire to further reduce
re-radiation. I don't think this tower is wide enough to require a 3-wire
"skirt."
In my pre-1985 broadcast days, a single drop wire worked well for detuning
grounded 25G and 45G style towers. These were usually 2-way radio towers
with little top-loading (pre-cell site era). Since these towers were rarely
1/4-wave at the BC freq., insulating the guy wires made a big improvement,
and the detuning circuit did the rest of the work. The only towers requiring
a 3-wire skirt were CATV or microwave relay towers, which were taller,
fatter, and had the extra loading of multiple antennas.
Gary
K9AY
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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