[TenTec] Omni VI/3 ALC problem?

[Rob Atkinson, K5UJ]

Okay, now it's my turn with an Omni VI question.

I have been having some trouble driving the Centurion to full output on some 
bands with the Omni VI.  Originally, the problem was driving it to 1200 
watts on 40 meters (it was fine on 80).  It always went to 1200 watts or 
more on CW during tuneup but on phone on 40 it would peak out at about 900 
watts.  As I wrote a few weeks ago, I thought I'd fixed it by shortening the 
feedline between the exciter and amp.  It turns out the problem is a moving 
target--the shorter feed caused it to simply pop up on a higher frequency.  
I put a swr analyzer on the end of the feed to the amp and keyed the amp so 
the analyzer would be looking at the feed going to the tuned inputs so I'd 
see what the rig sees when driving the amp.  I found that on good bands 
there was no reactance on the line.  On poor drive bands there was a 
reactive component of about 10 ohms (+- 2).  In all cases the swr was always 
very low (naturally--remember swr alone doesn't tell the whole story!).  My 
theory is that on phone, this X somehow causes the alc to kick in too much 
and limit the rig output but that sure seems like a stretch.  No probs on cw 
and the Corsair II drives the amp fine.  Any ideas for a solution?  All I 
can think of is a matching network between the amp and the rig which I'm not 
much interested in (I guess I could use one of those autotuners but I'd like 
to drive the amp without another tank circuit to fool with), or maybe 
there's an ALC adjustment?

If ur about to tell me to relax and live with it don't  bother--I'm aware of 
that as a solution and I'll do that if I have to, but for now I'm interested 
in getting some practical troubleshooting ideas for when I have some time to 
kill (it's more of a mild annoyance--not a high priority).  I also know that 
300 watts is some tiny fraction of a db gain--don't need to be told that 
either.

tnx everyone & 73,

Rob Atkinson
k5uj at hotmail.com

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