[App_rpt-users] RTCM audio interfacing options

[Tim Sawyer]

If you are using discriminator audio you don't have to set deemp=yes in
voter.conf because 13 - COR type = 0 (normal) will switch in the RTCM's
filter. With 13 - COR type = 1 (Ignore) the filter is not switched in.

You can use COR type 0 in non-voting applications if you want to use the
RTCM's squelch circuit which is quite good and MICOR quality. This has 2
advantages. You'll be able to see the RTCM's RSSI rather than just 0 and
255. Second, you can use turn the P/L on and off as the only output PIN
isn't 'anded' COR and PL. In this case you likely will need to set
deemp=yes in voter.conf.

Transmit audio is not pre-emphasize unless you have CTCSS enabled. If you
need pre-emphasis but no tone you can set a freq with 0 level.


On Tue, Jan 23, 2018 at 12:04 PM, Sam Skolfield <kj6qfs at gmail.com> wrote:

> 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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-- 
Tim WD6AWP
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