Open Source DMR Modem Implementation in SDR with GNU Radio and Codec2

55 threeme3 5 4/19/2025, 12:23:50 PM qradiolink.org ↗

Comments (5)

fsiefken · 57m ago
I wonder if Codec2 could be replaced by one of the low bitrate neural audio codecs, HILcodec and SementiCodec sound better at 2-3 kbps.

https://arxiv.org/pdf/2405.04752

https://arxiv.org/pdf/2409.14085

lpribis · 2h ago
I see this is only tier 2 for now (conventional channels) and not tier 3/trunked yet.

Are trunked networks ever used in amateur radio or outside of big commercial/government systems? Is there a standardized way to feed back channel info to the SDR frontend for trunked operation in GNU Radio? Eg. The control channel will tell the terminal to tune to traffic channel at X Mhz to receive or send a call, which requires reconfiguring the frontend.

birdiesanders · 1h ago
Trunked is essentially useless to HAMs, and we never really use it much. We have essentially everything that trunking was meant to solve for a company; large pre-authorized spectrum space, self-coordination in that space without having to get fcc involved. Use of 25khz FM where part 90 is now only 12.5 also is enabled by being a ham.
wolrah · 32m ago
> Trunked is essentially useless to HAMs, and we never really use it much.

I wouldn't say it's useless, but the utility is reduced because we typically don't have the density of users where two timeslots on a single channel becomes a real limiting factor. A repeater that's set up for local talkgroups on one timeslot and then open access on the second is generally more than enough unless you have a lot of people trying to use it at once, especially in a world where anyone who wants to can have their own personal hotspot for less than the cost of a HT.

Also the usual "ham not HAM" thing.

mschuster91 · 1h ago
> Use of 25khz FM where part 90 is now only 12.5 also is enabled by being a ham.

Y'all can use 25 kHz for repeaters? Here in Germany repeaters are 12.5 kHz only, allegedly due to a lack of free frequencies...