MMDVM Nano hotspot for DMR, D-STAR, C4FM, NXDN and P25

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Tim Kirby G4VXE looks at another useful and cost-effective digital voice hotspot.

 

 

Tim Kirby G4VXE looks at another useful and cost-effective digital voice hotspot.

 

When Moonraker were looking to stock a Multimode Digital Voice Modem (MMDVM) hotspot, there are so many to choose from that Chris Taylor G0WTZ decided to ask a real expert in the subject, Jonathan Naylor G4KLX for his recommendation. Jonathan recommended that Chris take a look at the BI7JTA models and this is what they have done.

Here at PW, we have already reviewed a very similar MMDVM device in the shape of the Zumspot-RPi. The MMDVM Nano should have the same capabilities as the Zumspot but we wanted to see how, if at all, the performance differed. If you would like a detailed description of what an MMDVM device can do, please refer to the Zumspot review (PW December 2018).

However, as a reminder the MMDVM devices are digital radio hotspots, with a transmitter power of around 10mW. They act as personal repeaters, so that you can connect to a variety of digital radio networks (D-STAR, DMR, C4FM, P25, NXDN) using a digital handheld. Excitingly, some cross-mode capabilities exist, from DMR to C4FM and NXDN, for example, and from C4FM to DMR, P25 and NXDN. Please note that the MMDVM doesn’t allow cross-mode contacts to and from D-STAR, although there are some reflectors that do allow this functionality. The Nano has the MMDVM board attached to a NanoPi single-board computer, which has WiFi built in. This means that you can power the hotspot from a USB port or power supply and pick internet connectivity from your home WiFi, or perhaps from your mobile phone acting as a Personal Hotspot.

 

First Impressions

The Nano is surprisingly small! It’s presented in a 3D printed case that has a slightly rough look to it but is robust and well-fitting. There’s a small window in the case for an OLED display as well as an RJ-45 network port, micro-USB connector for power, a port where the WiFi adapter is connected and an aperture for the micro-SD card containing the file system for the NanoPi computer.

Thinking that the Nano would be like the Zumspot, I powered up the device on USB and hopefully scanned the WiFi for a ‘Pi-Star-Setup’ WiFi network to appear. It didn’t and no new WiFi networks appeared. I have subsequently discovered that there were some bugs in the versions of Pi-Star that were current at the time, which may have prevented this happening.

Later, I discovered in the instructions (URL below) that if I had created a WiFi network on my phone called 888888-2G with a password of 0123456789, the hotspot would have connected to it!

https://tinyurl.com/y7z25al2

What I decided to do, however, was to connect the Nano into my router, using a networking cable and the RJ-45 connector on the Nano. I was then able to use Fing, a network scanner running on my smartphone, to find the IP address of the Nano. Then I was able to start to configure it from a web browser, using the IP address I had just discovered. In fact, the first thing I did was to edit the WiFi parameters so that it could connect to the house WiFi rather than being hardwired from the router.

It was at this stage that I discovered that the WiFi capabilities of the unit were not as I had expected. If I moved the Nano out of the room where the WiFi router is situated, the connection dropped. I asked Chris Taylor to check another unit to see whether this was standard across other models. He said no and that he had successfully connected to a WiFi router around 30m away. However, if you want to use a Nano somewhere that you feel the WiFi signal is weak, it may be worth you checking that you can return the unit if it doesn’t work as planned.

Once I’d worked through the networking setup wrinkles, Pi-Star setup itself was very easy, although I found the BI7JTA instructions rather less clear than the general Pi-Star setup instructions at the link below, which I would probably recommend as an alternative. By the way, Chris G0WTZ recommends the Nano.MMDVM support group on Facebook.

https://amateurradionotes.com/pi-star-notes.htm

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Something I did notice was that the NanoPi board was faster to restart than the Pi Zero W that I use with my Zumspot. This will be because it is a slightly faster processor.

 

Getting on the Air

With the hotspot configured with its frequency, I was able to try it on the air and quickly put it into DMR mode, connected to the Worldwide Brandmeister reflector 4639 and listened on the appropriate frequency with a DMR radio (I used an Anytone AT-868 for testing). Sure enough, I was able to make some test contacts. D-STAR was the same and I was able to connect the Nano hotspot to the worldwide reflector REF001C and connect using my Icom IC-E92 handheld. (Note that you must put your rig in repeater mode on D-STAR, albeit with a repeater shift of 0kHz, otherwise it will not work). Finally, I put the Nano into YSF (Yaesu System Fusion or C4FM) mode and connected the hotspot to the America Link ‘room’ or reflector, which worked well.

The nice thing about MMDVM-type hotspots is that you can be connected to, say, D-STAR, DMR and YSF networks all at the same time and the hotspot will change into the appropriate mode automatically as traffic comes up on the different networks. If you start listening to a D-STAR contact, say, you can ‘anchor’ it to the D-STAR system by waiting for a quick break in transmissions and transmitting a D-STAR signal with your handheld so that the MMDVM will not move over to, for example, Fusion in the middle of an interesting D-STAR QSO!

I was also pleased to find that I could use the cross-mode capabilities of the hotspot to go from YSF to DMR, NXDN and P25 systems as well as from DMR to YSF and NXDN systems.

One of the nice things about the OLED display on the Nano is that it shows you which mode is active and if there is a station transmitting, what their callsign is. You can also see the IP address of the hotspot, which can be useful at times.

 

Out and About

One of the very adaptable things about the MMDVM-type hotspots is that you can take them out and about with you, perhaps in the car (or even in a rucksack if you are walking), so that you can tether the WiFi to your mobile phone’s hotspot and listen to whatever digital network you wish. I used the WiFi configuration to add in the SSID and password for my iPhone’s hotspot, so that if I wanted to use the Nano in the car, I could. Sure enough, that worked fine and I enjoyed using the Nano when I was parked up at a local hilltop, being able to make contacts into the USA using the Fusion systems.

Updates of Pi-Star software are possible through the configuration dashboard menus and I successfully upgraded to the latest version of Pi-Star on the Nano.

 

Conclusion

The MMDVM Nano worked well as a hotspot and did everything I asked of it. The setup was a little more quirky than other MMDVM models I have used but once done, it worked fine. It may be that those problems were more a product of the Pi-Star software than the Nano itself. The WiFi performance was notably less than I would have expected but that was hopefully just the WiFi adapter on the review model. Apart from those reservations, I was happy with the performance of the Nano. If you are a digital radio enthusiast, you will almost certainly want to own an MMDVM-type hotspot because they provide a very flexible approach to digital radio, especially with the possibility of cross-mode connections.

Many thanks to Chris Taylor of Moonraker for the kind loan of the hotspot and for answering all my questions. The MMDVM Nano is available from Moonraker Ltd and costs £134.99.

 

 

This article was featured in the April 2019 issue of Practical Wireless