Try adding JP1 in the RTCM. This gives some gain to the squelch noise amp.

If that works you'll want to turn on the RTCM's BEW (#17 on the main menu). If it's not on that menu you'll need to download the proper firmware and upgrade. This help radios with low out of band discriminator noise not false the squelch on voice peaks. There 3 settings 0) off, 1) on, and 3) on with more aggressive locking.

But first make sure you can calibrate the squelch with JP1 in. Otherwise your SOL and there's no reason to upgrade. In that case you'll have to buy some other radios for your voters.

On Sun, Mar 27, 2016 at 2:12 PM, Skyler F <electricity440@gmail.com> wrote:

For a voter project, we got the hamtronics VHF receiver pretuned to the repeaters input frequency. The idea is to use hamtronics receivers for every voted receive site for equivalent audio characteristics.

http://www.hamtronics.com/r303.htm

When hooked up to the discriminator on the hamtronics board, I could not get the RTCM to calibrate squelch. It usually told me the audio was too low weather the RX level was bumped up or down. I then hooked it up to a motorola SM50 and it calibrated shortly after adjusting RX levels.

So... I hooked a cheap sound card up to audacity, and took a look at the spectrum of each receiver. The hamtronics obviously looks like it lacks high frequency noise on the discriminator output.

Here is the SM50 discriminator out:
amsatnet.info/SM50.png

Here is the hamtronics discriminator out:
amsatnet.info/HAMTRONICS.png

Here is an audio sample comparing them (you can probably guess which radio is first):
amsatnet.info/Sm50_hamtron_DISC.wav

Does anybody else have experience with hamtronics receivers?

Thanks,
Skyler KD0WHB

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