MMDVM and radio testing results

Today saw the arrival of the MMDVM and Arduino from Bruce in Canada.

Andy has the TX and RX setup and on soak test. So far there have been excellent results with the Motorola GM350 radios.

So now, I have a couple of tasks to complete:

  • Make patch cables
  • Do a Linux / MMDVMHost build for the RPi.
  • Borrow a ladder and move the antenna to it’s final spot (It’s 1.5m low at the moment)

Extra client-side functionality from the MMDVM repeater and dmrshark

Right from the beginning I wanted to be able to extend the basic functionality of the MMDVM DMR repeater beyond just simple voice traffic. Whilst BrandMeister and MMDVM are both great pieces of work, I’m not sure I agree completely with the BrandMeister architecture and the fact that pretty much all functionality is handled at the server, taking a lot of control away from the repeater keeper.

In my quest to be able to do more with the MMDVM from the computer side, I’ve been trying to get my head around the source code, because I’d like to be able to do things like filter talk-groups at the repeater and send DMR SMS messages.

During my research, I discovered dmrshark. Dmrshark uses libpcap to analyse the traffic flowing over a Hytera IPSC network and do things with the data gathered. It’s yet to be seen how much modification it will need to work with the homebrew repeater protocol but it could provide a useful tool for analysing what is going on, gathering data and responding to it.

I am particularly interested in the fact that it might be able to drive an SMS-based information system. Both SMS and IP data are currently under-utilised on Amatuer networks.

I built a system for information request and weather data transmission etc. for APRS a couple of years back. It seems to me that DMR SMS would enable this type of functionality whilst getting away from some of the limitations of APRS. APRS is outdated and does not scale well and there is much resistance to progressive ideas and development on the APRS network. DMR should be able to handle this type of system and voice traffic, with neither system causing any impact or degradation to the other.

All we need now is radios…

Yesterday I ordered the duplexer and the GSM switch (for remote shutdown).

We have reached the stage that all we require to get on the air are the TX and RX radios and a few bits of cable and connectors. I am estimating a cost of about £200 for two used Motorola PMR radios that are data capable.

If anyone has anything suitable, or wants to contribute to getting something that is, all help is appreciated.

GB7FR Update 13/04/2016

Andy G3UEU has been doing some great work in testing and setting up the RPi 2 with his spare DV modem. (Thanks Andy!) He say’s it is ready to go as soon as we have radios. He is also going to loan his spare DV modem for the repeater until the one I have ordered turns up.

Today, I have ordered a 6-cavity duplexer, pre tuned for the repeater’s frequencies, and the GSM power plug for remote shutdown.

We are getting there!

Repeater construction

In order to build a working repeater, the following equipment is required:

  • MMDVM board (on back order)
  • Arduino DUE (on back order with MMDVM board)
  • Rapsberry Pi 2 (Andy G3UEU has kindly offered one of these for repeater use)
  • Antenna (already have a Tram 1480 Colinear)
  • Power supply (Already have this)
  • GSM power switch for remote shutdown (going to order this)
  • TX and RX (I have been in discussions with G7TXU – Tony and G3UEQ – Andy about this)
  • Internet connection (I have 80/20 FTTC service with a block of IPv4 and IPv6 IPs already)
  • Duplexer (not yet acquired)

As can be seen above, help has kindly been offered by some local stations.