Number of Talkgroups

dva7564

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Jul 24, 2022
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Hi all,

Prospective buyer with a functionality question. Seems like everyone with one of these radios is impressed with the reception and seems like the software has come quite far.

Main question - how many talkgroups can be received at once? Ideally, I would be recording calls for import into/playback with rdio-scanner off of one P25 system. Is this more like SDRTrunk in that it can receive/record multiple talkgroups at a time? Or is this more like a traditional scanner that is always limited to playing/recording one talkgroup a time?


Thanks!
 

techlogix

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I would love a portable scanner that could receive multiple talkgroups at one time like SDRTrunk. I would buy it in a heartbeat. But like mentioned above, this device only does 1 talkgroup at a time.
 

btt

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I would love a portable scanner that could receive multiple talkgroups at one time like SDRTrunk. I would buy it in a heartbeat. But like mentioned above, this device only does 1 talkgroup at a time.
How much are you willing to pay? I could do a 4-rx channel, high-end receiver design. If you find enough users willing to buy a >$1000 receiver, I'm interested. I might be willing to do this as a crowd-sourced project as soon as parts return to the market.

edit: I should elaborate a bit since most probably aren't engineers here. SDR Trunk achieves multiple receive channels by taking in very wide chunks of spectrum (no narrow band filters) and then down-mixing by utilizing an NCO (numerically controlled oscillator) with digital mixer (complex multiplication) for each desired channel. The downmixed samples are then filtered, decimated, phase-locked, then decoded. This means you are processing bandwidth for hundreds/thousands of dead channels, all the time. It isn't efficient. If I do a multi-channel design, it won't be wide-band like this. It would be separate, well-filtered, narrow-band channels.
 
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techlogix

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I personally would have no problem buying one. I have spent quite a bit of money on multiple scanners. I only recently got into the SDR stuff. When I discovered SDRTrunk could listen to multiple talkgroups at once, I was hooked on it for my local tower. I can understand in some areas it may be way too much traffic but in my town, it’s only 2-3 channels at most that will talk at one time. During police pursuits, it’s amazing being able to listen to the multiple agencies’ channels. I also like being able to hear the different size ups for calls given to fire/EMS vs the more detailed size up usually given to PD. Ideally I would want it to be in my car and then I will just use SDRTrunk when at home but if it works well enough, I could see myself selling my Unication pagers and Uniden scanners to replace them with this new product.
 

FreqNout

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Ideally I would want it to be in my car
Since we are brainstorming here...How do you envision this high end portable device for listening in your car to 3-4 channels at the same time? Does the portable unit have 4 speakers or what audio interface is desired to meet your dream unit?
 

techlogix

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Since we are brainstorming here...How do you envision this high end portable device for listening in your car to 3-4 channels at the same time? Does the portable unit have 4 speakers or what audio interface is desired to meet your dream unit?
Since I have 4 scanners running in my office all the time, I’m pretty good at selective listening. Even when all are talking, I can focus on just one. I think the device would only need 1 or 2 speakers. I use SDRTrunk with 2 speakers and it automatically splits the active channels to left and right speakers. For example if fire and PD are talking at the same time, it will send one channel to left speaker and the other to the right speaker. If more than 2 are talking, it just adds them to the left or right speaker.
 

FreqNout

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Understood. I have used SDR trunk with the stereo feature. It is nice for 2 TGs. So, adding 2 TGs to each of the 2 speakers is how you see it working with 4 conversations. Got it. Thanks.
 

maus92

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If you use recording software, the talk groups are recorded in parallel but played sequentially. When it's busy, there can be a call queue, so playback is near real-time due to call processing. You can also listen in real time, but that's not practical as you would hear multiple talk group mashups, then the same convos individually. I theoretically have 9 channels that can be received simultaneously in my current test setup: 5 on a SmartZone system and 4 on a P25 system.
 

kb8q

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Ferndale, MI
How much are you willing to pay? I could do a 4-rx channel, high-end receiver design. If you find enough users willing to buy a >$1000 receiver, I'm interested. I might be willing to do this as a crowd-sourced project as soon as parts return to the market.

edit: I should elaborate a bit since most probably aren't engineers here. SDR Trunk achieves multiple receive channels by taking in very wide chunks of spectrum (no narrow band filters) and then down-mixing by utilizing an NCO (numerically controlled oscillator) with digital mixer (complex multiplication) for each desired channel. The downmixed samples are then filtered, decimated, phase-locked, then decoded. This means you are processing bandwidth for hundreds/thousands of dead channels, all the time. It isn't efficient. If I do a multi-channel design, it won't be wide-band like this. It would be separate, well-filtered, narrow-band channels.
I would definitely have interest in a unit that would contain 4-rx's. Especially if the software could dump the logs in a way that was consolidated.

It would greatly simplify what I'm doing with 3 receivers now and sometime this year I'll need 4.

The nature of what I'm doing is not portable. It's fixed and runs 24/7/365

James
 
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