Building your own MMDVM repeater

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Posts: 37
Joined: Wed Apr 11, 2018 9:05 pm
Location: San Antonio Texas

Building your own MMDVM repeater

Post by n5amd »

Hey all!

I wanted share my home-built repeater using analog Motorola CDM radios. My hope is that folks can see that you dont need thousands of $$$ to built a digital repeater for a local community to use. Currently this repeater is serving the San Antonio Texas area and has about a 25-30mile coverage using a simple mobile duplexer. I have instruction on how to build one on the link below. You can use this to either build a full blown duplexed repeater, or a simple high powered simplex hotspot. Either way, the more infrastructure the better. ... -repeater/

Last edited by n5amd on Sun May 05, 2019 4:06 am, edited 1 time in total.
Posts: 4
Joined: Thu Apr 12, 2018 12:25 pm

Re: Building your own MMDVM repeater

Post by G0ANV »

Hi tnx fer posting this article.
I've sent it to a ham friend in Fort Worth TX in the hope he will put a MMDVM Repeater together.
Posts: 7
Joined: Sat Dec 15, 2018 2:38 am

Re: Building your own MMDVM repeater

Post by KA9UCE »


I am thinking about programming a couple of Maxtracs for use with MMDVM, and my Pi-Star ZUM radio.
Duplexer is a cheap mobile unit, but the skirts are tight, and notch is deep.
Tuned for:
RX: 449.700 (high)
TX: 444.700 (low)

Radio systems engineering is my profession, so I would be happy to share data and testing equipment.
Motorola analog, digital, DMR, P25.
Kenwood analog, DMR, NXDN.
Icom analog, (not currently supporting any D-Star systems)
B/K Relm analog, digital
462.600/467.600, D432
444.700/449.700, D462
[email protected]
Posts: 8
Joined: Mon Mar 23, 2020 5:11 am

Re: Building your own MMDVM repeater

Post by WA1OKB »

Being a glutton for punishment.... I'm in the process of trying something similar.... But instead of a pair of mobile radios, I'm going to try and use a DRA818U transceiver board for the receive side... The board has pretty good receive sensitivity, and has AF_OUT for flat audio.... Doesn't matter that it's only 1w since it's on the receive side....
Posts: 5
Joined: Wed May 01, 2019 3:02 pm

Re: Building your own MMDVM repeater

Post by kf4eok »

could or would you share your receive and transmit code plugs with me. I am building two of these and I think that I am having problems with the code plugs. I hope someone sees this and sends me some code plugs to my email at [email protected]

I have two Zum radios and a stm32-dvm that I have on raspberry pi 4
Posts: 33
Joined: Thu Apr 12, 2018 6:08 am

Re: Building your own MMDVM repeater

Post by F5VMR »

If I can be of any assistance I have built and manage three homebrew DMR repeaters with the different modems. F5ZLR can be found on as will my articles on my own page F5VMR.
Happy building.
Posts: 5
Joined: Wed May 01, 2019 3:02 pm

Re: Building your own MMDVM repeater

Post by kf4eok »

I have built two of these and havent gotten either one working.
One is with the zum radio board and pi-star on a raspberry pi 4
One is with the stm32 board and pi-star on a raspberry pi 4
both of them have the same results. They are connected to the internet and dashboard shows activity. you can hear digital noise on a fm radio on the output frequency but it is like the digital radio is not hearing the signal.
This happens on both setups but using the same cdm1250 radios in duplex mode. For this reason I believe that it is the programming of the code plug on the tx and rx radios that I am trying to use as the repeater.
Is anyone using the motorola cdm 1250 in a setup like this for mmdvm? If so would you be willing to share the code plugs from your working setup?
My email is [email protected]
Any ideas of what I am doing wrong.
Many thanks
Posts: 2
Joined: Wed Mar 27, 2019 7:31 pm

Re: Building your own MMDVM repeater

Post by PD0HOF »

hi fellow repeater-enthusiasts

I have an old motorla repeater set (build in box with duplexer) (radio's are two GM340's)
used to be an analog system for the local authorities

I would like to build a MMDVM repeater out of it (just add a pi with mmdvm board)
now comes the fun part when I started I bought a mmdvm board, but I start to think its "faulty" or not suited?
at the moment I own this controller, ... JEALw_wcB
of corse it was the cheapest of them all hihi

does anybody has experience with this model?
can it be done?
if so, how do I do it?

other wise,
what kind do I need? (preferably something that does not break the bank hi)

I do have all the connectors, pi radios powersuply backup-battery and a housing to put it in.
now I just need some help glueing it all together

kind regards,
Milan Hofman
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