[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Skyler F electricity440 at gmail.com
Sun Mar 27 17:12:41 EDT 2016


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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