[AMPS] Tetrode Amp articles needed

[w8jitom@postoffice.worldnet.att.net]

> << 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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