> So the question is, is this a common problem? Am I doing
anything wrong? Could I do
> anything better?
This is a common problem. The problem is the system
configuration requires the radio output RF before the preamp
switches out of line.
This means the preamp has to handle nearly the full output
power of the radio or any amplifier BEFORE the preamp relay
drops and bypasses the preamp. If they did anything like add
a diode across the relay or didn't do there homework in the
switching system, it can be even worse!
You need to switch the preamp out of line before
transmitting and switch it back in line after a safe delay.
RF detected circuits can't do this.
In some designs, I had to add an intentional MMIC buffer and
attenuator pad to allow RF switching the preamp out. The
MMIC is rugged, and a pad of several dB limits the power
applied to protection diodes and the GAsFET drain. It is a
real PITA thing to design a preamp that won't fail from
being banged with high power RF while waiting for the relay
to transfer.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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