Hello. I am hoping to set up a portable standalone repeater for some digital modes with MMDVM and some old mobile radios, something I know has been done many times. However, I do not want it to be networked for ease of setup and some other reasons. It will be mainly used temporarily at events (ex, for a demo with my college club at a club event). Basically, I am looking to make this without a PC or Raspberry Pi running a host program. As far as I can tell, the MMDVM boards themselves are controlled completely via serial. So, instead of buying and hooking up a Raspberry Pi or similar, I want to jumper an MMDVM board to an Arduino and have it control the modem. However, I am having difficulty finding documentation of the serial commands used to control an MMDVM. I can't find such documentation on GitHub, and when doing a general internet search I can find a document called 'The MMDVM Specification' however it dates to 2015 and it is clear that most of MMDVM's functionality has been added since then. I know I could probably sift through the source code and figure it out from there, but I would really rather not. Does anyone know where I could find a list of the MMDVM serial communication commands, the baud rate, etc.? Making a little Arduino MMDVM controller with some LED indicators and some switches would be a lot cleaner and I would like it a lot better than a whole control computer I would need to SSH into, and I don't want to network the repeater anyway. Thanks!
Set up an MMDVM repeater without a network connection/host
dickie757
Wired
I dont think it will work. You would need two modems...one for rx radio and one for tx radio. MMDVM passes packets to the network or pistar. Pistar connects to siteconnect network, bm, tgif, qrm, etc. In your case, the subscribers will do all of the modeming
On the other hand, running a straight repeater without PL might work. You just have to make sure pre-emphasized/de-emphasized audio is put in the right place. In other words, you dont want any filtering of rx audio being passed to tx radio.
I know Ive messed up wording, so some one help me explain what I mean.
On the other hand, running a straight repeater without PL might work. You just have to make sure pre-emphasized/de-emphasized audio is put in the right place. In other words, you dont want any filtering of rx audio being passed to tx radio.
I know Ive messed up wording, so some one help me explain what I mean.
There’s off the shelf MMDVM models for making repeaters that are full duplex. There’s YouTube videos on it I’ve watched.
I’ve done a straight through analog repeater before with just some jumper wires between accessory connectors. Worked pretty well once I set the mic gain to the right amount.
dickie757
Wired
Ya, I have one, but I dont think the modem is doing anything from rx to tx. All it does is put the digital audio onto a network. The tx'ing subscriber is the radio making it digital.
I don’t mean a hotspot. I mean a device that hooks up to 2 mobile radios, uses one as a receiver, and one as a transmitter and plugs into the discriminator tap for the receiver and the data in for the transmitter. So it does repeater functionality and also ties into a network (which I don’t need). I know they exist- I’ve seen them set up on video and there’s plenty of literature about it. There’s just not info about doing it without a Raspberry Pi or PC.
Here’s an example. I basically want to make this but without a Pi controlling it.
dickie757
Wired
Never said anything about a hotspot. I have a modem that connects to a RPi or PC, actually, two of them.
The only reason to use the modem is to put the rx audio on a network, and to get network traffic into the airwaves. If you do not have any intention of networking the repeater, you do not need the modem or a RPi.
The only reason to use the modem is to put the rx audio on a network, and to get network traffic into the airwaves. If you do not have any intention of networking the repeater, you do not need the modem or a RPi.
Project25_MASTR
Millennial Graying OBT Guy
You can totally use it to create a standalone digital repeater. I know several doing it to create ad-hoc P25 repeaters using teh DVM Project's stuff.
Have you seen it be done without networking?
Project25_MASTR
Millennial Graying OBT Guy
Yes.
Ok well if you have any tips or know of any resources on how to do it without networking and preferable without a Pi that would be great.
electric2u
Member
Did you ever get it to work? I'm looking at doing the same thing. I have two ic-121s that I would like to create a stand alone DMR repeater no network. Dumb question can a DMR radio get repeated though a analog repeater and work?
dickie757
Wired
The biggest thing to overcome is sub-audible tone. Amateur 25 kHz has plenty of bandwidth to deal with digital audio signal. It will sound great, too.
Nope. I know it’s possible but without knowing how to interface it I don’t know how to do it without a Pi.
You can repeat a digital signal through 2 analog radios, but you’ll need to use an MMVDM, because digital radio is more than just repeating the signal. The repeater talks back to the transmitting radio for DMR anyway telling it “go ahead and transmit” and I think there’s some sort of signal processing in P25 too. That’s where MMDVM comes in
electric2u
Member
So more or less I need a Stm32 DVM Pihat or a ZUM radio MMDVM-Pi board and wire it in to the back of the radio ( two pig tails off the back board on the radio in to the MMVDM)
Yep. I’m just wanting to figure out how to do that with an Arduino or something controlling the MMDVM board instead of a Pi.
electric2u
Member
if you have made this work, I would love to know what products you used. I would like to be able to do this as stand alone
Well, so far I haven’t and I made this thread to try and figure it out. If I do, I’ll post an update here assuming the thread is still open.
electric2u
Member
I did get this email from repeater builder
You can use one of our MMDVM boards and a Raspberry Pi with Pi-Star or WPSD software and it should work as a stand alone
repeater just fine with no network necessary.
You can use one of our MMDVM boards and a Raspberry Pi with Pi-Star or WPSD software and it should work as a stand alone
repeater just fine with no network necessary.
Oh, alright. I heard that if started without the host Pi having an IP address it will not start the repeater. Also, I’d like to find a way to control it with an Arduino microcontroller, not a whole Pi. But that is interesting. Thanks
You need to assign the Pi a static IP address. Then you can use it standalone with no Internet. The Pi is needed to be the brains for the modem. The RepeaterBuilder board is the one that I am using. Awesome stuff from those guys.