Digital Radio

I have acquired many radios in this first year, mostly to experience the different digital modes. I did start with DMR, and have DMR mobiles in the car as well as a DMR handheld. I really enjoy DMR, and its multiple uses, plus the FDMA use of the frequency (2 simultaneous slots) just makes sense to me. My first hotspot was the simplex hotspot, seen below. This worked well, and I had a blast talking all around the world.

Then I had the urge to buy another radio, which brought me into D-Star. I quickly realized simplex is NOT ideal for these hotspots, so I pulled a Pi3 off the shelf and ordered a duplex board. Oddly enough, the first duplex MMDVM board I bought was lost in the mail, and I ordered a second from a different source. Both showed up, and I set the second one on my parts shelf, unknown if it will ever be used. A quick program and testing, and duplex D-Star was a whole new world. I used it for quite a while.

Most recently I dabbled into Yaesu System Fusion, which is a FMDA, but instead of two voice slots, there is a voice narrow on what would be slot 1 and a data stream on what would be slot 2. Most interesting, you don't pre-program your radio to access the groups/reflectors/rooms you want to talk to. Instead, you just program uplink and downlink frequencies, and let that data stream do the rest of the work. Immediately after getting into this mode, I remembered the spare MMDVM board sitting on a shelf collecting dust. I quickly ordered another Pi3 and put together my third hotspot.

I do continue to use all three modes regularly, and intend to add other modes as I acquire radios. P25 and NXDN are within the shortlist, though they are commercial modes and do tend to cost a bit more to get into. Both are supported by PiStar, the software that controls the hotspots, and would likely build additional hotspots to cover these additional modes.

I understand that digital modes tend to scare some licensed amateurs. If you have any questions, do not hastate to email me. I would be happy to help answer your questions.

Quick History of Digital Radio

There are many different digital radio modes used in amateur radio, many come from the professional LMR and public safety systems, while others are developed by the amateur radio community for the amateur radio community. It should be noted, in the commercial LMR and public safety systems, the FCC has previously mandated narrowbanding (12.5kHz channels) and is currently mandating any new systems be ultra-narrowband (6.25kHz channels), while amateur radio is permitted (not required) wide band (25kHz) usage.

DMR is widely used, and comes from the commercial LMR systems. DMR uses TDMA (time division multiple access) to achieve ultra-narrowband equivalent by providing two talk paths within a single 12.5kHz channel.

APCO-25 is the current leader in public safety radio. Phase 1 systems meet the narrowband mandate using C4FM modulation, but not the ultra-narrowband mandate. Phase 2 systems uses TDMA to achieve the ultra-narrowband equivalent.

D-Star is an amateur radio standard created by the Japan Amateur Radio League.

YSF is a version of C4FM modulation that can support simultaneous data & voice, or wide band voice.

There are other systems available, but I do not have any experience with these. Some include Tetra and NXDN. I claim no ownership to any logos, and only show them to aid in recognition of the systems discussed.

YSF (Duplex)

Usually Connected to XRF330 (#83603)

(Died recently due to water being poured on it)

D-Star (Duplex)

Usually Connected to XRF330 (XLX330A)

DMR (Simplex)

Connected to many full time talk groups on the Brandmister network

311070, 3139, 31390, 31391