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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.

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birdiesanders 4 days ago | parent | next [-]

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.

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wolrah 4 days ago | parent | next [-]

> 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.

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ac29 4 days ago | parent | prev | next [-]

> part 90 is now only 12.5

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).

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wkat4242 4 days ago | parent | prev | next [-]

I don't think it's useless at all. It would be amazing, roaming the country and never having to worry about frequency settings. And in that case you do need more time slots. Tetra would be nice with 4 slots. I know in Holland and Germany they're experimenting with it.

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mschuster91 4 days ago | parent | prev | next [-]

> 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...

	▲	colanderman 4 days ago \| parent [-]
		In the US frequency allocation within each band (including repeaters) is left up to regional spectrum management organizations (which have no legal authority). So it varies by region. 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.

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kotaKat 3 days ago | parent | prev [-]

Not really.

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 ;)

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Calwestjobs 4 days ago | parent | prev [-]

many SDRs can RX/TX spectrum many times wider than you think is required in here.

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 )