In article .net,
"Doug" wrote:

"Meindert Sprang" wrote in message
..
Much snippage...
.
Only if you feed the 1/2 in the low impedance point, which is halfway in
the
middel. Since this is impractical on a boat, feed it at the endpoint. But
at
the endpoint of a 1/2 wave, the impedance is very high so you need the
least
capacitance you can get at the antenna feedpoint. So GT15 is ok, but keep
it
1" away from any grounded or other conductive area (like strapping the
GTO15
to the uninsulated lower part of the backstay with tie-raps... BAD
PRACTICE).

Meindert
PE1GRV

Is the 1" just a rule of thumb or is there some engineering calculations to
support this distance? I see many sailboats with 1" varnished wooden dowels
or even plastic hair curlers with cable ties used to keep the GTO15 off the
uninsulated backstay wire. I have a feeling wider spacing would be even
better.Comments please.
Doug K7ABX



The 1" is a "Rule Of Dumb", that does allow for some decoupling, but
doesn't really decouple the antenna for the parallel Grounded backstay.
One can calculate the capacative interaction between the two, or one
can just use the "Rule of Dumb" and let the antenna tuner correct for
the extra capacitance. Just understand that most autotuners will not
like the extra capacitance on the output, and this will tend to widen
out the 1/2 wavelength tuning problems that all endfeed autotuners have.

Bruce in alaska
--
add a 2 before @