> << I would too, if it worked properly. Unfortunately, those controls
> << more often than not allow the exciter to overshoot on leading edges.
>
> So a external ALC circuit such as one in a AB1 amp is going to feed back to
> the exciter and cut the drive from the exciter quicker ?
If you read my post again, you'll see I said an ALC system
with a SLOW decay will help this problem. You might get one
occasional leading edge overshoot, but the overshoots caused
by brief pauses will be gone.
> << I've measured ICOMs that produce 300 watts PEP when set to 25 watts
> << output during the leading edge on SSB. My IC-706 hits 150 watts plus
> << on some bands (no matter what level I set the power control at), my
> <<FT-757 hits nearly 180 watts, but my IC 751A is OK.
>
> This "leading edge" is still gonna be there with the alc circuit from the
> amp.
Absolutely, that's why a long ALC hang time, fixed external
reference voltage (to limit no signal gain) and proper matching of
exciter power to PA drive power is important.
Like many problems, it's not as simple as one carte blanche
answer.
> I still suggest, to not overdrive a AB1 amp...use the power control on the
> exciter.
> I think some people are too close to the forest to see the trees.
> Terry - W6TG
It won't work in every case Terry. The power control (if you read my
posts I mentioned this) is almost always ALC derived. All the power
control sets, in most rigs, is a reference voltage in a comparator
system for ALC threshold. It would be much better to use external
bias, a PA with proper drive requirements matching the rig, and an
external ALC system that turns on when the tube is close to being
overdriven (and has a long hang time).
The reason the rig has overshoot in the first place is because its
INTERNAL ALC system has too long an attack time.
73, Tom W8JI
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