Probably the sampling diodes on the SWR board. Get some 1N34 diodes (if I'm
remembering correctly) and replace all on the board.
A nearby lightning strike probably damaged one without causing any further
problems.
73,
Gary ~ AB9M
________________________________
From: TenTec <tentec-bounces@contesting.com> on behalf of Gary Follett
<dukeshifi@comcast.net>
Sent: Thursday, October 10, 2019 5:07 PM
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Corsair SWR goes high as power is increased
Has anyone else seen this before?
He Corsair II operates perfectly into a dummy load, all bands.
The owner’s complaint was that the radio shows high SWR at high power, a
condition I could not replicate into a dummy load on the bench.
However, when I tried a real antenna, things changed a LOT. I observed exactly
what the owner saw, but only when the SWR was a LITTLE high, maybe 2:1.
These are photos from my spectrum analyzer, full power and about half power.
The radio is pretty clean with 14.6 MHz harmonic about 40 dB down.
It is clear that things get really bad as power goes up and the “SWR” readings
are the result of all of this out-of-resonance signal, which is why the problem
only shows up on a resonant load, not on a resistive load.
I did perform driver bias adjustment and final amplifier adjustment with no
change in performance. Prior to adjustment, the bias for the final was quite
high at 2+ amps, well over the 500 mA specified in the manual. I set it to the
proper 500 mA. Still no improvement.
Gary Follett
W0DVN
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