DMR Hotspot

There is a lot of blogs, forums and place to get information about various aspects of our hobby. Ham Radio, as you all know, is a diverse hobby with a lot of different ways to  enjoy it. This post is going to be about my learning and stepping in DMR. As with most of my posts, this is aimed at someone just looking at and thinking about diving into DMR. If you are a seasoned DMR operator, then you likely know all this already.

A friend of mine brought an inexpensive TYT MD-380 DMR radio to a club meeting and told us about DMR. He uses it a lot when he travels around a two state are for his job and loves it. After that, I decided to order the same radio and see what DMR was all about.  This friend sent me his code plug and when I looked at it I was lost. He had all the repeaters for two states, lots of talk groups and lots of operator call signs. It was a lot to digest for someone who didn’t know how to program a DMR radio.

I decided to take a step back and learn some more about how DMR works and how to do the programming. I wanted to start simple and begin my code plug from scratch. The closest DMR repeater to my house is about 20 miles away and with all the hills around Arkansas, I cannot hear it with the HT antenna. I figured putting together my own hotspot would be the ticket as I have three Raspberry Pi’s sitting around doing nothing but collecting dust, so acting on some advice from more experienced hams, I ordered a DVMega board to go with one of the Pi’s.

I asked a friend with a 3D printer to print this case for the Pi and DVMega from Thingiverse.

IMG_0246

The completed Pi, DVMega combination put together and ready to go. Yes there are two screws missing. I don’t know that I need them so I left them out.

For storage for the Pi, I used a Sandisk class 10 32GB micro SD card that I already had. It is important to use a decent storage card so the performance isn’t worse than it needs to be. One of these cards is less than $15, so it is not very expensive compared to the cost of the entire hotspot project.

One could download Raspian and install all the software separately but there is an image already created that is very popular called Pi-Star. It is essentially Raspian with MMDVMHost, DStarRepeater and other software included. It is an easy way to get everything you need for DMR, DStar, P25 and more digital voice modes.

Pi-Star can be downloaded from here. Once the image was downloaded, I used the Linux dd command to write the image to the card.

After inserting the card into the Pi and booting it up, there are two very important steps. The first is to expand the image to use the entire card. When first written, a small portion of the space is used and a command needs to be run to expand the file system to use the rest of the space. That command is pistar-expand. The second important thing to do is to make sure the image is updated. The Pi-Star creators provide two commands for doing that. pistar-update / pistar-upgrade which are similar to the Raspian apt-get-update and apt-get upgrade commands but do so for the operating system and the software included in pi-star.

To setup the Pi-Star software, I followed along with this page:

https://www.toshen.com/ke0fhs/pi-star.htm

There is a lot of information on this site in addition to this page related to DMR. It was worth browsing around and finding information that I didn’t know.

After configuring the hotspot, I was able to verify that it connected to the BrandMeister Network.

The next step was to program the TYT MD-380. I had to choose a simplex 70cm frequency. After consulting the band plans and looking at the Arkansas repeater council page, I was able to choose one to use.

I won’t go into a lot of detail on programming the radio as there are a lot of YouTube videos and web pages describing that process.

I listen to the Hamradio 360 Workbench podcast and they use a talk group that I programmed into a channel and was able to hear some of that traffic. I also made a call and confirmed that I was able to transmit on the talk group as well as receive.

My next step is to find other talk groups that I might want to listen to, and determine how I will use DMR going forward. I am planning on taking the hotspot on business trips and possibly use it in the car for DMR mobile. I’ll figure that out as I go along.

Overall the process was not difficult, but took some time researching how DMR worked so I could understand the programming better. I used many web resources along with several YouTube videos. I still have a few more bookmarked to watch but I am getting a handle on it.

Edit: As I learn more about DMR and gain experience, I’ll probably post again on the subject in the near future.

Comments and questions are welcome.

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2 Comments

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2 responses to “DMR Hotspot

  1. David WB4ONA

    Which DVMega board did you use, where did you get it, and what did it cost? IMO these Hotspot boards like the DVMega are outrageously over-priced for what they are. Did you consider the likes of a Jumbospot board from ebay or similar instead?

    • I have the single band (UHF) DVMega. I got mine from hamradio.com. I did not consider the Jumbospot etc. I asked some experienced hams what they recommended and DVMega was the first one on the list. When I ordered it, there was availability problems with the Zumspot, but seems that’s resolved.

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