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Re: [Amps] AM mode

To: nw7us.heliophile@gmail.com
Subject: Re: [Amps] AM mode
From: Jim Barber <audioguy@charter.net>
Reply-to: audioguy@charter.net
Date: Fri, 11 Sep 2009 17:20:29 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
The "25% rule" has worked in the past. Some comments, tho:

. It would be interesting to know what the community thinks is a good 
set of operating conditions for an AL-80A on AM. Considering the AL-80A 
has only mediocre cooling for the rated input I'd personally lean far 
toward the conservative. I have an SB-1000, (a Heathkit clone of the 
AL-80) and have run it at 100 watts carrier *output* and 100% modulation 
(~ 400 watts PEP) without incident, but even then it gets pretty warm. 
For everyday use I run the larger amps on AM and leave the SB-1000 for 
SSB work.

. Much of the common literature regarding running AM with amplifiers 
assumes high-level modulation. It's unlikely the IC-7000 modulates 
anywhere near 100% on AM, but I haven't measured one to know for sure. 
(I haven't seen a popular solid-state rig yet that does, with the 
exception of the Flex 3K and 5K which aren't typical)

My .02,
Jim, N7CXI


Tomas Hood wrote:
> Ok - I wanted to confirm what I think is the proper way to run a
> linear amp (mine is the Ameritron AL-80A) in AM mode.
> 
> If I set my Power Output level to 25% of the maximum carrier power
> rated for my amp (85 watts) (25% is 21 watts on my Icom IC-7000),
> then, if my mic gain is modulating well, I will not run over the peak
> of 85 input to the Amp.  Is that correct?  When I speak into the mic,
> should I see the power output fluctuate between the carrier-only power
> (just less than 200 watts), to something a bit higher?  Talking should
> cause the power output to "modulate", correct?
> 
> Thanks for helping me clarify.
> 
> 73 de NW7US, Tomas David Hood - Bitterroot Valley of Montana
> 
> Singer/Songwriter/Guitarist : http://tomasdavidhood.com
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