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