> I remember having to replace the coax inside a number of
amps back then. One
> end of the braid would overheat to discoloration and melt
the dielectric
> which of course shorted the coax. *IF* I remember
correctly this was the
> lead that went to the transfer relay and was a common
problem with that
> particular amp. I've even forgotten the model now, but I
sure fixed a bunch
> of them.
Probably because they returned circulating currents in the
tank loading cap to the chassis via the braid.
Not the same braid location I was speaking of, which was
from tank taps to band switch, but the root cause would be
the same.
The case I'm speaking of is when I did a consulting job for
Dentron/Amp Supply. Their engineer was using braiding
removed from RG8 to install ten meter taps in amplifiers.
Without running an amp I looked at it and said "that braid
will probably overheat".
After a disagreement we made a bet on it. We ran an amp and
sure enough after a few minutes the braid started smoking.
Replaced it with number 14 solid and it was cool.
I had the advantage of knowing it caused problems because of
earlier experience where it was used in other RF
applications. Back then we measured RF heating to determine
RF resistance, and it was about the same as #16 wire at 30
MHz.
73 Tom
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