Back to Radio – Digital Voice

Hotspot for DMR, D-STAR, Fusion, and P25
Hotspot for DMR, D-STAR, Fusion, and P25

There are more than 700,000 FCC-licensed ham radio operators in the United States, but only a fraction are active in the hobby at any given time. I’m often one of those inactive people, but every few years I get interested in some new area of the hobby.

Five years ago it was D-STAR, a digital voice mode. This time it’s DMR (Digital Mobile Radio), another digital voice mode mostly used for commercial and public safety applications that’s being somewhat awkwardly retrofitted to the amateur radio paradigm. While the learning curve with DMR is a bit higher, the low cost of entry makes it an easy gamble. It’s not that digital voice is necessarily difficult, but a good portion of the documentation and know-how for both modes is hidden away in haphazardly organized “Files” areas spread across unconnected Yahoo Groups, most of which require membership. Anybody approaching DMR or D-STAR with simple and reliable methods like scouring Google for technical information is in for a frustrating experience.

Roadblocks aside, my venture into DMR circled back through D-STAR and all the development I’d missed over the past several years. There’s a lot of symbiosis between DMR and D-STAR activity, mostly in the form of the little low-cost Raspberry Pi computers. My first goal was to marry these two modes in a single Raspberry Pi box with as many options as possible. The result is the hotspot pictured above.

The hardware consists of a Raspberry Pi 3 B board, a DVMEGA board seated on the GPIO pins, a DV4mini attached directly to USB, and the red DVAP attached to USB by cable.

Also pictured are the ultra-cheap Tytera TYT MD-380 radio for DMR, the Icom ID-51A Plus for D-STAR, and the Yaesu FT2DR for System Fusion.

The software starts with the latest Western D-Star image using Raspbian Jessie Linux, including ircDDBgateway and D-StarRepeater for use with the DVAP and DVMEGA, and the DV4mini application. Then I added MMDVMHost for use with the DVMEGA on DMR, D-STAR, and System Fusion. The SD Card image also functions fine on the Raspberry Pi 2 B board.

The DVMEGA board along with the MMDVMHost software is at the heart of this hotspot and can be used for all three modes. Using radio control alone, it connects to the BrandMeister DMR network, the YSF Fusion reflectors, and any D-STAR reflector. The DV4mini will handle D-STAR and DMR, but I’m mostly using it to connect to the DV4mini FCS System Fusion reflectors. It also technically makes this an APCO25 and DPMR hotspot.

Since most DMR and D-STAR networks are closed-source systems, there’s really not much else to do at the moment other than hope for new developments and enjoy some interesting QSOs with other hams in the meantime. One possible exception is the D-STAR X Reflector network. It uses open source software and operates without any real central authority. I’ve set up two XLX reflectors, one for WARN and one for W8IRC – but without an automatic DNS distribution scheme, I doubt the X Reflectors can ever gain full traction as a mainstream competitor to the original DPlus network. I’m on board to try though.

(Originally published on June 21, 2016.)

Edit 2016-08-02: I bought a Yaesu FT2DR System Fusion rig, so the DV4mini is now getting lots of use again in the hotspot.

Edit 2017-02-25: I purchased an Icom ID-51A Plus to replace the old Icom IC-92AD boat anchor for D-STAR. Much better!

Thanks to Andrew K4AWC for nudging me in the direction of DMR.