A week or two ago, someone asked about the F.P. ALC light coming on too
readily when operating their Argonaut V. I thought I'd pass along an
experience I had last weekend with my Omni VI ALC with the hope that what I
did might help with the Argo problem:
I had noticed earlier last year that when operating LSB on 40 meters the
Omni could not really drive the Centurion to full rated output. I'd get
around .9 to 1 kw out. Since that's certainly not the end of the world I
simply lived with it. At around 75 w. the ALC would kick in and limit
output even with the PA Ic pot all the way clockwise. On 75 all was fine;
the Omni generated plenty of RF and easily drove the Centurion to the full
1.2 kw output without straining and the Ic in the 3 o'clock position. OTOH,
my Corsair II did not exhibit any idiosyncrasy of this type and drove the
amp fine on both bands. I finally got around to fooling with this and since
the only thing that was different between the two rigs was their lines to
the amp, I removed the Omni line and replaced it with one that matched the
Corsair's. The Omni had been working with a short 5' run of 58U and I put
in 10 feet of Cablexperts 8U (their 1318 stuff). The Omni put out
noticeably more power on 40 after that. Since I'm not a feedline
genius I can only guess that on the short run the rig was seeing a standing
wave or reactance at 7 mhz that a longer run diminished somewhat and this
somehow affected the ALC. I tested the short 58U on an ant. analyzer into a
dummy load and there weren't any obvious faults with it.
So anyone having this kind of problem might try lengthening or shortening
(if possible) your feedline & see what happens.
73,
Rob Atkinson
K5UJ
k5uj@hotmail.com
BTW, a friend of mine in Pa. emailed me a short mp3 file of myself
ragchewing on 40 meters a few days ago. I had never heard myself off a
receiver at a distance and was blown away by the tx audio on the Omni.
Without any eq. it sounded (for a SSB rig) almost like a broadcast station.
And this with a nonDSP rig. Kudos to Ten Tec.
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