Distinguished Associates:
Can anyone tell me how much isolation I should expect from the diode T/R
switching circuits on the low pass filter board in a Corsair I? In other
words, what is the normal signal level at the RX Antenna input at the low
level driver board (connector 26, I think) for a given output power?
I've been working on a Corsair that has most of the switching components
damaged as if by lightning. I thought I had it all fixed but when I ran the
rig up to full power, there was sufficient power fed back from the final to
the low level board to take out the PIN diodes located there. I've now
identified and replaced even more defective components near the output (on
the low pass filter board) and everything seems to be working even for the
brief time that I ran the power up near the maximum on lower frequencies.
Now, I'm seeing a reduction of about a 1000 between the output voltage at
the antenna connector on the back panel and the rx antenna connector on the
low level driver board, i.e., for 100V out, the residual signal making its
way through the 1N4007 diode T/R switch and reaching the low level driver
board is about 0.1 Volts at the lower bands. Isolation at 10-meters is not
as good, maybe a factor of only 100. All measurements are made with a scope
and 10X probe. Is this level of isolation typical for this radio?
Thanks,
joe, WA4GIR, looking forward to getting this radio working on the CW
bands because of all the good things I've heard about it.
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