[TenTec] Corsair SWR goes high as power is increased

[GARY HUBER]

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 at contesting.com> on behalf of Gary Follett <dukeshifi at comcast.net>
Sent: Thursday, October 10, 2019 5:07 PM
To: Discussion of Ten-Tec Equipment <tentec at 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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