[arm-allstar] PTT Delay idea

[john at qso.com]

I've been trying to integrate one of these SSM2167 boards into my repeater
now.
I can't figure out how to completely defeat the noise gate however. On low
level transmissions off the network, the audio cuts out. 
I need to defeat the noise gate while maintaining the gain. Also I need to
find a schematic of the little red board itself, not just the chip so I
know how to tailor it to my needs. I found that 50K resistor for R1 works
for the compression ratio I need, and I've tried all different values for R2
including the no more than the recommended 5K (1mV) threshold, but I can't
detect a difference in the noise gate.  Any documentation would be great and
appreciated.

John
N7OKN
n7okn.com



>John,

> We are using that board in our radio-less nodes that are about to be
>released. You really need some kind of limiting/compression when you just
>hook a mic to the CM1xx chip. It works very well. Anyone that is building
>their own radio-less node should be aware of this. You either need to
>reduce the level such that peaks do not clip or use some kind of
>compression.
>
>
>*73 Doug*
>
>*WA3DSP*
>
>*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*
>
>On Tue, Mar 5, 2019 at 1:52 PM "John Griffith via ARM-allstar" <
>arm-allstar at hamvoip.org> wrote:
>
> Perfect. Looks like from the documentation, that increasing the value of
> the  AVG capacitor increases the recovery time without affecting the fixed
> 30 ms attack time. That's actually what I was looking for. I think I'll
> order one and a project box to put it in. Impressive that that chip will
> amplify signals all the way to 1MHz.
>
> In the meantime, is there a way within the programming of app_rpt to send
> a short tone or noise burst then the PTT signal on every key-up?
>
> -----Original Message-----
> From: David McGough <kb4fxc at inttek.net>
> Sent: Tuesday, March 5, 2019 11:02 AM
> To: john at qso.com
> Cc: arm-allstar at hamvoip.org
> Subject: RE: [arm-allstar] PTT Delay idea
>
>
> Okay....I think this board (or a similar one) will solve your ALC issues.
> I haven't measured the actual dynamics of this board, with the supplied
> component values.  These values could be adjusted to allow wide
> modification of all the various parameters, or course.  I would guess the
> attack is under 1mS and release maybe 100mS. I know on a radioless node,
> with a electret mic attached and without this board, you can easily
> pop-your-P's, even with the levels set low. With this board, no spattering
> at all!!!
>
> Here is a datasheet for the SSM2167 chip:
>
>
>
https://www.analog.com/media/en/technical-documentation/data-sheets/ssm2167.
pdf
>
>
> 73, David KB4FXC