Experimenting with our Pi-2 and DMR Ham Radio

   To try somthing new and to use tech from our RC car we made we decided to add a MMDVM "hat" board to out PI 2.(Nicked as a 'hat' as it mounts on top of the Pi boards)  A MMDVM(Multi-Mode Digital Voice Modem) works with several ham digital modes to make a hot-spot.  A hot-spot is a link from a DMR radio to the internet that is linked to a worldwide ham radio DMR network.  It is thus possible with DMR to talk to other Ham operators around the world while both being on a mere handheld radio.  The mode we are interested in is DMR(Digital Mode Radio).   It is the least expensive mode to get into as its technology is well established for commercial radio communications.  Even so we will not be getting a DMR radio to use right away and will wait for a used or bargain model.

   Towards this effort we plan to add the MMDVM and a 2.4" Nextion resistive touch screen($16.40) to show freq, mode, power and tx/rx to our existing Pi 2.  We purchased a clear shell for our RC car and plan to try to mount the screen under its wind screen, thus using the RC car as a base for our hot-spot.

   Right now the plan is to make the hot-spot togather as a useful electronic project.  At a later point we will get a used DMR radio, yea we can get a new Baofeng for $49 but a used TYT MD-380(new $82) or similar model would be a better radio.  Patience gets the best deals, and we're still building the hotspot so are in no hurry.  Even more patience and saving an extra $30 would get us a new and better radio than the Baofeng.

   April 23, 2019 😕 I just saw a used TYT MD-380 for $69 on Ebay without the antenna or battery,  that could only sell to someone who already has an extra battery and antenna as the cost of buying battery and antenna would cost more than a new radio.  Personally we like most, would rather buy a new one for $13 more rather than a used one and missing parts. 😕

  The reason we need to use a hot spot is that in Eugene there is perhaps only one DMR repeater(kc7rjk) although I have not got a response from the owner.  DMR repeaters are usefully hooked up to regional or national networks(ie. PNW and Oregon DMR fb group) and thus limits communications of peer to peer or specific groups of people(called rooms) you may with to talk to (for 10 minute spans).  I have made Friends with a DMR group from Germany I would like to talk to without having to be at the mercy of the common networks.  So far we have only messaged members on Skype and talked via a phone PTT app and one phone call with a member.

   Update May 9, 2019  All done and seem to work and says Idle as expected, but  I would have thought the IP-Address would get past "Logging onto network and  "Initializing  wait" would change to the current IP address.  The real test is if we ever get a radio, but it was fum making somthing useful of the old car project anyway.

Here area few pics:

Old Pi-2 powered RC car with a new clear shell as a dust cover will
 house and show the 2.4 Nextion screen of the DMR MMDVR hotspot.
"Calling car K7VIQ...." 

DMR mode screen that I like and would like to see frequently.
Screen created by G0FEA

Idle mode. We will see a lot of this screen
 until we actually get a DMR radio.
Screen created and shared with other hams by G0FEA

Nextion screen with MMDVM hat board and
70cm antenna mounts to a Pi board.

Antenna MMDVM hat board and 70cm antenna

Kathy holding our previous car project,
the foundation for its new life.

The 1/18 scale shell we hope to use with our car for dust protection
and for the project to seem a bit more finished.

Not our car but the same shell painted to show detail.