[GreenKeys] ARRL Handbook TU Limiter Circuit wanted

[Ralph Mowery]

It has been a long time ago that I read the articles by Hoff.  I think that
he decided way back that the limiter was not the way to go IF you had other
circuits that were automatic threshold/decision correction and some other
circuits.  However for the hams and ones with limited abilities or budgets
then the limiter circuits were the way to go.   His designs of the later
tube circuits and the ST-6 were the standards to shoot for back then.
Simple and inexpensive enough to build but worked very well.  One good thing
about the limiter/discriminator circuit is that the tones do not have to be
spaced apart and on frequency as close.  Way back then very few had a good
way to build and calibrate filters and tone generators for 170 Hz shift.
Now an audio frequency to high RF frequency counter is a few bucks and
computer software can generate and detect audio frequencies for free.

Ralph ku4pt






-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Harold Hallikainen
Sent: Wednesday, January 20, 2021 4:59 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] ARRL Handbook TU Limiter Circuit wanted


> You have to remember that only one tone is sent at a time.  So it is not
> comparing the amplitude of the mark to the space,but rather the tone to
> the
> noise.  So if the tone is just slightly out of the noise it will be
> boosted
> well above just the noise of the other tone frequency noise at that time.
>
> Ralph ku4pt

Thanks! I need to run a Spice simulation of this. The peak amplitudes of
both the tone (in one filter) and the noise (in the other filter) would be
the same after clipping, but the tone filter output would be less when fed
with the clipped noise than with the clipped tone. But is this an
improvement over not clipping the signal?

Again, I need to simulate it!

Thanks!

Harold