Go digital with a System Fusion hotspot

Use the DV-Mega and raspberry Pi to go digital at home

Many radio users have wound up with D-Star, DMR or System fusion capability bundled with a radio that they acquired at some point. Digital repeater coverage is not so prolific leaving many without the ability to use this digital mode technology. But there are ways to gain a digital connection at a low cost by using digital hot spot!

There are a number of digital hot spot solutions on the market, some work right out of the box, some need to be plugged into a PC and some require the use of a Raspberry Pi or a Blue Stack Micro. Here we will talk you through the DV-Mega and Raspberry Pi solution. 

This page does not intend to replace the materials already freely available on the internet, it is simply intended place all the resources required in one place, while also providing a clear overview of the assembly and setup process.

DV-Mega and Raspberry Pi can give you an all-mode digital hotspot

I made two of these units, one based on the original Raspberry Pi and one based on the version #3 model. Both worked well, the later Pi version offered faster boot up time and more responsive O/S navigation. If you can, go for the later Pi model.

Hardware required for this project:

  • DV-Mega (http://www.dvmega.co.uk/)
  • Antenna (for DV-Mega) - Single or dual band
  • Raspberry Pi (any version)
  • 16Mb SD card
  • WifI dongle (if not built into the Pi)
  • Power lead for the Pi
  • Plastic Pi enclosure

Tools required:

  • Windows PC
  • SD card programming dongle or slot
  • Epoxy glue (for 2&3 Pi versions)
Raspberry Pi (original version) with DV-Mega
Raspberry Pi (version #1) with DV-Mega fitted

Assemble the hardware

The DV-Mega comes with basic fitting instructions which explain how to fit the modem board to the Raspberry Pi. The DV-Mega board fits directly to the Raspberry Pi I/O pins as shown below, it is very simple to install. 

Raspberry Pi3 ready for DV-Mega fitting
Raspberry Pi3 ready for DV-Mega fitting
Raspberry Pi3 ready with DV-Mega fitted
Raspberry Pi3 ready with DV-Mega fitted

The DV-Mega board is supported by it's connector socket with the use of a small support spacer. This spacer screws through the PCB on the early versions of the Raspberry Pi, with later models this spacer will need to be glued to the PCB.

Before gluing, first fit the support post to the DV-Mega, apply the glue the the base of the post, then placed the board in position. I found that I had to fit an extra washer between the DV-Mega and the support post as the spacer supplied was not quite long enough. I initially used super glue to attach the support post, this did not work at all. I then used epoxy glue which was much better and worked well.

I observed ESD precautions when handling the Raspberry Pi and DV-Mega boards. I think this is important to avoid any potential future issues.

DV-Mega hotspot spacer
DV-Mega spacer

Modify the Pi box

You are going to need a box to protect your digital hot spot. There are plenty on ebay and Amazon, I avoided the metal cases to avoid issues with the built in WiFi (Pi3 only). Most Pi enclosures will accommodate the DV-Mega PCB, but do think about this before purchasing.

Which ever case you choose you're going to have to drill a hole for the antenna. Accuracy is very important when drilling the antenna hole, so it's worth triple checking before drilling. Identifying the correct position on a clear case is easy, however if your case is not clear then some thought will have to go into identifying the correct position. A small pilot hole will allow for a sample check to be made before committing to the final cut. A 16mm hole cutter will make a clean cut in most materials and should leave you with just enough space to fit the antenna. No other modifications are needed.

DV-Mega and RSP3 modified box
DV-Mega and RSP3 modified box

Flash the SD card image for Yaesu System Fusion (YSF)

For the next step you will need to flash your SD card with the custom image provided by KB5RAB: https://spaces.hightail.com/space/se06G/files . Full and detailed instructions are provided with the image, it's important to follow the instructions to the letter to avoid problems, they are very well written and easy to follow so this should not be a problem.

 

The basic procedure is outlined below for reference:

  1. Use the recommended utility to format an SD card of 16Gb or larger (this is needed to maximise the available space).
  2. Download, unzip and write the KB5RAB image to the SD card using the recommend image utility.
  3. Boot the Pi off of the SD card, add a WiFI connection if required.
  4. Follow the KB5RAB instructions to switch off D-Star and DMR, enable YSF. This requires some simple editing of various text files (this is not difficult to do so don't worry).
  5. It is important to also read the 'Read me' file that will be located on your new desktop. This will advise you to expand the files system among other things to help improve performance.
  6. The image comes pre-loaded with TightVNC so remote access of you DV-Mega hot spot will be available as soon as you have established a connection.
  7. That's it!

Using Wires-X on a FD1XDE

Coming soon!

Range

The DV-Maega website says the unit is fitted with a 10mW transmitter. A range of about 100 metres can easily be achieved with the stub antenna supplied with the unit (with limited obstructions etc). Initially I had my handheld radio set to 'low' power which was limiting range, when I turned this up to 5W the range increased. It's also possible to fit an antenna with a higher gain to achieve a greater range if this were needed, I fitted my FD1XDE stock antenna to the hotspot to test this. I achieved a line of site range of 500m! I don't know why anybody would want to do this, but it was fun to test these things.

Summary

I have really enjoyed this project. It's just a great way to explore a modern mode without relying on a local digital repeater.

It did occur to me that these digital hotspots may be of particular interest to Foundation licence holders, global communication can be achieve at very low power settings.

A great project and highly recommended.