Don’t let the lack of a repeater keep you from playing with DMR or another digital mode. Keep reading to find out how
This post continues the conversation of DMR radio in my series. In the first video I looked at the Retevis RT82 DMR dual band handheld radio. Part two I talked about building your own DMR code plug, and in part three, we’re going to discuss one option for connecting to the world of DMR or Digital Mobile Radio if you don’t have easy access to a DMR repeater.
What is a Digital Radio Hotspot
DMR repeaters are springing up everywhere. There are currently over 850 operational or proposed DMR repeaters in North America. But if you don’t live in a large population area, you may find your DMR coverage lacking. So one method to access the DMR network is a hot spot. A hot spot is an IP digital radio gateway. That is, a hot spot contains very low power transceiver that is connected to a computer and the internet to give you access to the myriad of DMR repeaters and reflectors. Basically, if a repeater is connected to the Internet, you can most likely access it with your hot spot. This can be a boon for those outside the range of a repeater, travelers that want to talk back home, or if you are deep inside a building and can’t get a radio signal out.
So when you start searching for hot spots, you’ll notice quite a array of selections. Some are standalone, some plug into a computer via the USB port, and some connect to a small computer such as an Arduino or Raspberry Pi. If you are looking for the simplest solution, a standalone unit like the SharkRF Openspot may be the best choice. It’s self contained, and once configured, doesn’t require any computer intervention. But it can be cumbersome if use during travel is your main concern. Then one of the USB models like the DV4mini, which plug into the USB port of your laptop would be appropriate.
Since I’m a bit of an experimenter, I chose the build-your-own approach. Upon recommendation of a friend, I purchased a DVmega module that plugs into the Raspberry Pi miniature computer. Since no software comes with the DVmega, he pointed me to the Pi-star Digital Voice Software. Pi-Star is a comprehensive solution that supports not only DMR, but also D-star, System Fusion, P25, and NXDN. In fact Pi-Star has become quite complete and will run with just about any board that follows the MMDVM or Multi Mode Digital Voice Modem standard. So you can go with the DVmega board or get one of the cheaper and newer ZUMSpot boards that are now available.
DVMega and Pi-Star Combo
You can also purchase DVmega kits that contains all the parts you need, along with a software image on a SD card, but sourcing the parts yourself can be fun and I saved about $40 by purchasing the pieces separately. So putting the whole thing together was relatively easy. The first step was to download the Pi-Star files and create an image on a micro SD-Card. This was probably the hardest part of the whole process as you need to perform a few command line processes. But the Pi-Star site had pretty good instructions and the entire process only took about 20 minutes.
Once that is done, you can start building your hotspot. Put the Raspberry Pi into it’s case. I purchased a developer’s case, so I’m going to have to modify the cover so my antenna fits, but there are Raspberry Pi & DVmega specific cases if you are looking for something cleaner. Next install the DVmega. It sits on four of the pins of the 40 pin GPIO interface. Then put the Micro SD card with the Pi-Star image into the slot, attach the antenna, network cable, and connect the power. That’s all there is to it.
when you first power up your DVmega and Pi-Star combo, you’ll need a hard wired network connection. Everything is done in the browser window. From the configuration screen you can adjust your settings, add your callsign and DMR ID, and set up the wireless networking. You can also select which digital modes you’ll use. In addition to DMR, Pi-star will also support D-Star, System Fusion, and others. So you’re not locked into any one system. Also on the DMR side of things you can access DMR+ reflectors and Brandmeister Talkgroups. It’s really a full featured solution for someone looking for a hotspot.
Using the hotspot is pretty straightforward. You’ll program your radio with the simplex channel and specific talk groups or reflectors you’ll want to use. I put all my hotspot channels into their own zone. Then to bring up a reflector, first select the talk group on the radio and transmit for about one second. The hotspot will connect to the reflector. Now that you are connected, put out your call and see who responds. To change reflectors, select your talk group and briefly transmit. To unlink from a reflector, briefly transmit to talk group 4000. It’s pretty much the same procedure as you would do on a DMR repeater.
So bottom line, The DVmega and Pi-Star combination is a great choice for adding a digital radio hotspot to your home station. Don’t let the lack of a DMR repeater in your area prevent you from experience the fun of digital radio; roll up your sleeves and give Pi-Star a shot.
Are there any questions you have hotspots or DMR? Please leave them in the comments below.
Links and Resources
DVMega UHF DMR/DSTAR/Fusion Hotspot:
Raspberry Pi 3 Board:
Pi-Star Digital Voice Software:
Pi-Star Initial Setup (W1MSG)
Retevis RT82 DMR Dual Band Handheld Radio:
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