An audio limiter is a poor choice for SSB as filtering the various artifacts
is extremely hard even digitally.
Many rigs have a decent RF processor built in that is simply not set
correctly or deliberately abused. Ive even used the ones in the TS-940 and
950SD on AM after setting things up with a scope and SA and then receiving
excellent reports from a few of the highly critical denizens of 75M. It
doesnt take much to increase the presence substantially when using an AM
filter and a good mike.
Carl
KM1H
----- Original Message -----
From: "Dan Mills" <dmills@exponent.myzen.co.uk>
To: "Rob Atkinson" <ranchorobbo@gmail.com>
Cc: <amps@contesting.com>
Sent: Monday, January 02, 2012 1:16 PM
Subject: Re: [Amps] IMD
> On Mon, 2012-01-02 at 11:50 -0600, Rob Atkinson wrote:
>> This is why it cannot really be used to limit peak power. The audio
>> has to be tightly limited with a broadcast grade audio limiter, but
>> most hams don't want to spend the money on one.
>
> It does not actually take much of a limiter, the expense in broadcast
> limiters is in getting as close to 100% mod as possible, which is
> actually a secondary consideration for us.
>
> A clipper made from couple of diodes back to back across the audio line,
> followed by a lowpass filter will get you most of the way there,
> particularly if preceded by a compressor (THAT Corp do a very nice chip
> that can be trivially configured as a compressor/limiter/gate).
>
> The filter will of course introduce some overshoot and ringing, so a few
> stages may be indicated, but that is still only what a dozen or so
> components.
>
> Or a pair of SL670s or similar and a 445Khz ceramic filter plus a few
> diodes makes a dandy RF speech clipper/filter combo.
>
> I might draw one up and publish it somewhere.
>
> Personally I consider any ALC voltage to be an indication that something
> is not set up right, you know the amps power rating and power gain, so
> you know the required peak drive power, program that into the exciter
> and leave the ALC line unhooked (My exciter does NOT overshoot, some do,
> be careful).
>
> A reverse power sensor after the amp is a good idea if you go this way
> as the amp now has no way to fold back the exciter drive power.
>
> 73, Dan.
>
>
>
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