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MMDVM Repeater Issues.

Posted: Mon Apr 06, 2020 4:41 pm
by wb8vtw
I got a MMDVM repeater board last week. I cannot get it to work correctly.

In when receiving local RF in simplex mode the BER is all over the place. From .3% to 5% + from one local xmission from the HT to another. The TX audio decode on the HT is intermittent also when listening to TG91 for instance I have tried an Icom IC-F121 mobile and the Icom 706mk2g. Should not be such a problem to dial it in. I set the deviation to the same level as the little Jumbo Hotspot.

When I switch the hotspot to duplex mode the HT decodes the call information from the internet on the screen but there is no audio. It does not detect the local transmission from the HT either.

I am running the MMDVM board with a Raspberry Pi Zero W. I wonder if the Pi Zero is running out of snot because of its instability/inoperability.

The MMDVM board I am using is shown in the attachment.

FWIW, my Jumbospot with a Pi Zero runs great.

Once I get the MMDVM to work properly, I am going to try interfacing it to a UHF GE Mastr 2 repeater. It has a direct FM exciter which will hopefully work with the DMR data.

Thank you for reading.

Re: MMDVM Repeater Issues.

Posted: Mon Apr 06, 2020 5:23 pm
by M1DNS
For a duplex setup you'll need two radios, one tx one rx. So if you've only got a single radio attached, I'm not surprised it doesn't run in duplex mode. Set it for simplex.

2nd. Just because a radio has a six pin data plug, doesn't mean it'll run as a digital node radio. Not every radio is suited. A friend of mine tried a 706 a while back and gave up as he couldn't get reliable results with it.

3rd the zero should work fine. It's only when using the dashboard interface, and bootup times they get a little bogged down. General MMDVM duties, it'll cope fine.

Sent from my SM-G935F using Tapatalk

Re: MMDVM Repeater Issues.

Posted: Mon Apr 06, 2020 7:45 pm
by wb8vtw
Thanks for the reply. I realize that with only one radio it will not run FDX but I expect that it should transmit the signal when it is received from the internet, which it does, sort of. It shows the callsign of the person on the HT display but there is no audio. It also does not decode the local signal when it is in RX mode receiving the signal from the HT. I was told by other groups that COS is not used in DMR. I am not using COS but I can add it.

When in simplex it almost works but when in RX mode the BER is all over the place, sometimes .5% and other times it is 5% or greater. Key the HT one time it is acceptable, next key it is unacceptable. When listening to it on the HT, it has many dropouts.

I am using the Icom 706MK2G with the audio going in the 9600 input. Also tried an Icom IC-121s using the OPC 617 cable.

I am having basically the same issues with both RX and TX on both radios.

Re: MMDVM Repeater Issues.

Posted: Sun May 24, 2020 11:27 pm
by wb8vtw
I replaced it with a Repeater Builder STM32 DVM Pi Hat and all the problems went away. It was easy to install and calibrate.