Building an MMDVM hotspot on a budget

I bought myself a new handheld at the Newark rally earlier this year, an Anytone AT-D878UV to use on DMR. When I went on holiday in October, I took a couple of copies of RadCom with me and in one of them there was a review of my handheld. The author mentioned that he’d used it through a hotspot and this got me thinking because although there’s a DMR repeater near me, I’d never played around or experimented with hotspots. In fact, I’d never even seen one!

I like learning about new things so I contacted the author of the review asking for recommendations about hotspots and he suggested the Zumspot as being a decent pre-built hotspot that’s easy to get going. I dutifully ordered one while I was away and it was waiting for me by the time I got home.

Setting it up was very straightforward and within a few minutes, I had it all up and running and working perfectly with my handheld. I quickly learned all about the different modes it can be used with and spent some time upgrading it to the latest version of the software and fine tuning it.

I decided that I’d like another hotspot to use with D-STAR as there are many reflectors not available through the local D-STAR repeater and I thought it might be interesting to listen to some of them.

Rather than buy another Zumspot I thought I’d try and buy all the parts needed to assemble one myself and see how cheaply I could do it.

There are lots of MMDVM modems available on eBay so I just picked this one at random and ordered it. It wasn’t quite the cheapest but it was within a few pennies of the absolute cheapest. I paid £14.07 but I see that the same module from the same supplier has now dropped to £13.39.

It arrived quicker than expected as well – I ordered on the 1st November and it was delivered on the 13th November which I thought was pretty good considering it came from China. Unusually, the online tracking worked as well.

This is what I got:

MMDVM Hotspot Support P25 DMR YSF 32 bit ARM Processor for Raspberry Pi XY from eBay
MMDVM Hotspot Support P25 DMR YSF 32 bit ARM Processor for Raspberry Pi XY from eBay

The two sets of pins are for the GPIO header on a Raspberry Pi and the SMA aerial socket needs soldering to the board. The size is perfect for mounting on a Raspberry Pi Zero W and I had one spare so it only took a few minutes to solder the header and the socket in place and I quickly had a unit ready to go.

MMDVM Hotspot attached to a Raspberry Pi Zero
MMDVM Hotspot attached to the Raspberry Pi Zero

I wrote the SD card with a Pi-Star image, put it in the Pi and booted it. I’m not going to go into the details of how to write a card or configure Pi-Star as there are many places on the internet showing how to do this. The site by Toshen, KE0FHS is the best I’ve found for Pi-Star resources and you can visit it here. It took me about ten minutes to set everything up and reboot it.

A lot of hotspots come with little screens on them. In the limited time I’ve had the Zumspot, I really don’t look at the screen at all so I didn’t include one as part of my build.

This homebrew hotspot is working as well as the Zumspot. It doesn’t come in a fancy case, it doesn’t come with a screen but neither of those are important to me as I just want functionality.

Here’s a full breakdown of the cost:
MMDVM modem from eBay – £14.07
Raspberry Pi Zero W – £9.60
Raspberry Pi PSU – £8.00
16Gb SD card – £5.99

Total cost – £37.66

I could have built four of these for less than the cost of the Zumspot.

I’m not saying that people shouldn’t buy commercial hotspots but just wanted to demonstrate that it’s very easy to get the parts separately and assemble a fully working hotspot.

This entry was posted in Amateur radio, Construction, D-STAR, DMR. Bookmark the permalink.

5 Responses to Building an MMDVM hotspot on a budget

  1. Dave says:

    Pi-star rocks, it’s so easy to build a hotspot using any Pi with a 40 pin header. Very cheap if like me you have older versions of a raspberry Pi knocking and power supplies. Latest build cost me £14, they are so cheap I have one for each mode.

    • g6nhu says:

      Hi Dave,
      Yes, I already had everything needed for the build except the MMDVM modem so this actually only cost me £14.07. I added the prices for all the individual parts so people could see what the bottom line cost would be if they were starting from scratch.
      73 Keith.

  2. John says:

    I did the same, built one with same components to dedicate to mobile use.

    Used this beautiful clear case from Amazon. It comes with two tops, one with a hole for the 433 mHz antenna.

    https://www.amazon.com/gp/product/B07TWNSQ29/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

    73 John

  3. David Noakes says:

    I’m intrigued enough to build one myself. Sourced the bits on ebay and downloaded the software to an sd card. When the parts have arrived, will let you know how I get on!

    • g6nhu says:

      That’s good stuff, David. I don’t claim to be an expert by a long shot but if you have any problems, give me a shout and I’ll try and help.
      73 Keith.

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