>
>We don't get much static buildup here in the Northeast, so I don't think
>that would have been the cause. I have Polyphaser suppressors on every
>cable, but don't know if they would shunt a static discharge. Anybody know?
I am not sure about the Polyphaser units. But just stick an ohmmeter
on both SO-239s and look for a short on one side and put that towards
the antenna.
I know the ICE ones DO show a short circuit on one side and that ICE
has a patent on some of the static discharge feature.
I think the ICE ones have an RF choke and a gas tube to ground
on the antenna side, plus a DC blocking cap. But I don't recall
the exact values at the moment. Somewhere around here is a
schematic of the ICE unit that I reverse engineered--but I have
no clue what I did with it!
A LOT of the faulting in multi/multi is due to RF from one station
getting into the SWR detector in another station (whether it is
an amp or just a barefoot exciter) and shutting the station down.
When I was on the XR0Y trip I demonstrated this to one of
the ops. I put the barefoot 40M rig at 100 watts into its antenna.
Whenever we keyed the 80M barefoot rig, the 40M output dropped
to 50 watts as the SWR protection circuitry mis-interpreted the
80M coupled power as reflected power on the 40M system.
And then add a 13dB amp to the mix and you can see the trouble--
especially in situations with antennas that are not particularly
frequency selective--such as a tribander or dipole. Monoband
yagis with hairpin or gamma matches are much less prone to this
sort of problem.
At some level the RF picked up by an 87A into its PIN diode
circuitry when it is in the RX mode can cause damage--the
same way that RF into a separate RX antenna that is not
protected can damage the transceiver. Typically seen on
Beverages on a separate RX only antenna.
73--John W0UN
|