> The Micor Chip squelch is a well known circuit with action/operation > probably based on voice band energy/information and its detection > against other information (or lack there off) and/or noise.
The M6709 is basicly 2 op-amps, AC to DC rectifier, a window comparator and a audio switch. R/C filters external to the chip work with the op-amps to create band pass filtering that passes high frequency noise which is then rectified and compared to set levels at which point it is deterimned whether there should be a fast squelch closure (5 to 15mS) or a slow (about 150mS) one. hmm, Repeater-builder is down at the moment, but I suggest reading: http://72.14.253.104/search?q=cache:XBKnL-j-32wJ:www.repeater-builder.com/rbtip/micorsquelch.html+motorola+m6709&hl=en&ct=clnk&cd=1&gl=us > So the better beast would be to use a dual circuit like the Motorhead > Noise Integrator for your COS/COR logic and the voice band and/or > second squelch circuit for the voice audio gate. Hey that's what > Motorola does/did in the Micor and the MSR-2000. > > Don't be confused by a dual fast/slow squelch circuit operation > being the same as the integrator. I am sorry, but I am confused. What you are discribing sounds more like 'AND' squelch only instead of a PL deck it uses a VOX circuit in concert with a tradidional squelch board. Micors didn't do that, I have no experience with the MSR-2000 though. > Sometimes it's all a mute point if you "hide" or gate your repeater > controller receive audio behind an audio delay module. Like PL decks, audio delay lines just hide problems until someone goes to use the repeater. In some controllers having a delay board is more trouble than it is worth. Some only use it to eliminate DTMF tones, some have no provisions to mute audio into the board so feeding the controller with raw discriminator audio results in a 'front porch' squelch tail. Unless programed to what the delay of the line is most all will have a 'back porch'. And 75mS of delay does nothing to hide a 600mS squelch tail. Having a variable length squelch tail is also a dandy audible S-meter. > So.... What's in your wallet? At the moment I am running a GE MASTR-II base coverted to full duplex with the capacitor 'bi-level' mod. It is no replacement for the Micor squelch chip though.
