[GreenKeys] ARRL Handbook TU Limiter Circuit wanted

[Bob kb8tq]

Hi

The 741 op amp came out in 1963. Poly Packs had parts “for cheap” not more
than a couple years after that. Once you had cheap / simple op amps ….. this 
all changed in a big hurry. 

Bob 

> On Jan 20, 2021, at 5:54 PM, Ralph Mowery <rmowery42 at charter.net> wrote:
> 
> 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
> 
> 
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