[App_rpt-users] RTCM audio interfacing options

Sam Skolfield kj6qfs at gmail.com
Tue Jan 23 15:04:21 EST 2018


Hi Jessie.
Yes, for voting and/or simulcasting, you obviously need to provide raw
discriminator audio and modulator audio.

This is will be a non-voted repeater.

On Tue, Jan 23, 2018 at 7:41 AM Jesse Lloyd <ve7lyd at gmail.com> wrote:

> Well, if you want it to vote it'll have to be discriminator rx audio. If
> not, I'll use which ever squelch I deem to be superior. The motorola 2
> level squelches are typically pretty good, but you have to open the lid on
> a GM300 to adjust it. If that's ok, then I'd use that.
>
> For pre-emph, if you want simulcast with PL you have to let the voter make
> the PL tone. Otherwise I prefer using the mic in as it has nice a nice
> audio filter response and limiter circuit. Just a note for the GM300 you
> should adjust the max deviation when programming them into the ham band.
> The UHF ones I find change quite a bit with frequency. Sometimes you'll
> also have to make an adjustment to the PLL reference voltage to get it to
> lock up for Tx.
>
> Cheers,
> Jesse
>
> > On Jan 23, 2018, at 3:32 AM, Sam Skolfield <kj6qfs at gmail.com> wrote:
> >
> > Greetings,
> > I've been playing with RTCMs and VOTER boards for almost 5 years now,
> and I'm very happy with what I have in service. I've built a multi-site
> voted system, and more recently a non-voted hub that ties together repeater
> controllers at a few sites.
> >
> > I'm helping a friend but together a RTCM / pair of GM300 repeater, and
> got to thinking about audio options. There is more than one right way!
> >
> > 1. Discriminator audio to RTCM, set deemp=yes in voter.conf (causes
> hardware de-emphasis in RTCM circuitry)
> > RTCM TX audio to GM300 Flat audio input, use chan_voter software
> preemphasis by specifying txctcss and txctcsslevel=0 in rpt.conf
> >
> > 2. 1. Discriminator audio to RTCM, set deemp=yes in voter.conf (causes
> hardware de-emphasis in RTCM circuitry)
> > RTCM TX audio to mic audio, letting radio do pre-emphasis.
> >
> >
> > 3. 1.De-emphased audio from GM300 (JU551 set to B)  RTCM
> > RTCM TX audio to mic audio, letting radio do pre-emphasis.
> >
> > 4. 1.De-emphased audio from GM300 (JU551 set to B)  RTCM
> > RTCM TX audio to Flat audio input, use chan_voter software preemphasis
> by specifying txctcss and txctcsslevel=0 in rpt.conf
> >
> >
> > All four of these combinations should theoretically produce "flat"
> system response, but I'm sure all four yield slightly different results,
> given different corner frequencies in hardware/software de-emphasis /
> pre-emphasis and different input/output impedance combinations.
> >
> > Has anyone experimented with these combinations?
> >
> > 73
> > --
> > KJ6QFS
> > Sam Skolfield
> > _______________________________________________
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-- 
KJ6QFS
Sam Skolfield
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