depends on device, on one hand there are handheld radios which have small ARM for UI and control of dedicated radio chip, and then there are mobile phones/laptops/tablets with so much neural processing on board that it can have model sounding like person/celebrity of your choosing.
Are the bands really so crowded (think on 70cm?) that we can't afford the bandwidth for something a bit more HD?
Hf is still pretty busy I think but I don't do that. No space for antennas in the middle of the city.
But anyway there's definitely space on 70cm. The band plan would have to be redesigned though for wider channels. There's even more space on 13cm. Literally nobody uses that. There used to be some amateur TV but that's gone too.
And yes it's annoying that in this day and age digital radio still sounds way worse than ordinary FM at the same bandwidth.
It is designed to occupy similar bandwidth and have similar performance so that existing LMR spectrum planning assumptions continue to apply.
If you want HD audio, or better weak signal performance at the cost of audio quality etc, you need to design something different.
[1] Work the world with DMR: Digital Mobile Radio (2022):
https://www.hamradio.com/detail.cfm?pid=H0-019172
[2] WHAT IS DMR?
https://www.motorolasolutions.com/en_xp/solutions/what-is-dm...
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.
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.
This is wrong. 25kHz part 90 licenses are still available so long as the system meets the minimum efficiency standard (19.2kbps or better for 25kHz).
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...
Leveraging dvmproject, dvmhost, and the FNE bits, hams can operate their own APCO Project 25 trunking systems with commodity MMDVM hardware and link them across the Internet. You can use various MMDVM boards, use a v.24 serial link to a Quantar repeater, etc...
https://github.com/DVMProject/dvmhost
Ain't nothing wrong in running a single voice-on-control channel simplex hotspot to experiment with P25, or link to bigger systems ;)
Try to look at this small enthusiast SDR receiver - http://g4wim.proxy.kiwisdr.com:8073/ / http://kiwisdr.com/public/ you can see that simple 350$ radio can have 100s of "channels" visible/receivable at once. (digital modes are available in bottom right "toolbar", in top right corner, drop menu called "extensions" )
so with (different) SDRs you no longer need to choose one channel and listen to it, you can receive 200 channels at once, storing that data and choose what channel you want to decode later
or decode multiple radio stations realtime at once, even each with different mode (AM/FM/Olivia/USB...) and you can even (UNIX) pipe data from it, to programs not designed for ham / sdr use. data is just data as soon as you have it you can do anything with it. you can even write program/script to send email/notification/sound when specified callsign makes call/connects to trunk. for billing purposes...
or BTS/repeater can listen to 50Mhz wide part of spectrum 400Mhz-450Mhz AT ONCE realtime so no "tuning" necessary. for example 2000$ USRP can do that (but you need amps, filters etc to make full BTS )
Here is the allocation for eastern New England for example: https://nesmc.org/docs/nesmc_bandplans_2023.pdf On the crowded 2m band we have 20 kHz for major repeaters and 9 kHz for smaller ones.