Well, first, my post was directed to the post that started the
thread. Yes you can engineer a DSP based Squelch circuit if you want
but you have to measure noise sooner or later. Now, if you want a
squelch circuit followed by a delay network will eliminate ALL of
the squelch noise and would be sweet, but the squelch circuit STILL
works the same.
73
AC0Y
--- In Repeater-Builder@yahoogroups.com, "skipp025" <[EMAIL PROTECTED]>
wrote:
> You can't beat a really good squelch circuit. Much
> as I always seek real alternatives, the dual function
> Motorola squelch circuits seem to be some of the best
> designs (there is more than one dual function Motorola
> squelch circuit). Fast detecting - mute/gate time is
> the desired animal.
>
> Spectrum has a semi decent squelch circuit relative to
> what it is.
>
> I'm not happy with the slower Hamtronics or Maggiore
> squelch circuits although they do work just fine. Slow
> squelch circuits are not a major problem when you run
> many of the optional audio delay circuits to remove
> the crash noise. Even an old ACC RC-850, RC-85 and
> an RC-96 controller with an audio delay board would
> clean up the more horible squelch circuits (The VHF
> Engineering Receivers)
>
> Hence I seek to speed up the squelch gate action of
> our new Maggiore 224 MHz repeater. An external squelch
> board is probably the most practical answer.
>
> The COS or squelch layout described below is not an
> every circuit thing, but it might be typical of many.
>
> Sometimes the high pass filter is a band pass filter
> and the detected output is compared to energy at low
> and voice frequecies. Response times tend to be much
> better (faster).
>
> The common LM-324 and similar op amps can make a nice
> squelch - audio mute circuit. You just have to weigh
> in your time vs money/resources to pick your poison.
>
> I'm in the process of engineering up a sectional
> squelch pc-board for squelch, audio gating - line
> driving, ctcss with and/or COR/COS detection. One
> simply populates the desired section for their needs.
> More as that developes...
>
> The trick is to make it fast using the Micor
> Squelch circuit as a relative bench mark.
>
> cheers,
> skipp
>
> (ps: A 500mS squelch tail would drive me crazy...)
>
> > Bob Dengler <[EMAIL PROTECTED]> wrote:
> > At 6/10/2005 06:56 PM, you wrote:
> > >Lets face it, COS or what ever you want to call it is nothing
more
> > >than a VOX circuit that works on high frequency noise. first the
> > >audio goes through a High pass filter of some sort then through
an
> > >amplifier then to a detector circuit that drives a transistor
> > >switch. OH by the way, the switch is used to mute the receiver
and
> > >viola a squelch circuit is born.
> > >NOTHING DIFFICULT ABOUT IT.
> >
> > ...unless you don't want to hear long 500 millisecond squelch
> > crashes. Just ask the engineers that designed the Micor or Mastr
> II
> > squelch circuits.
> >
> > Bob NO6B
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