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.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|