I decided to fork gqrx on the BlueTail Technologies github repository and added a hack to change the display axis to show actual power levels in dBm (decibels relative to a milliwatt) based on the current LNA / Mixer / VGA settings. The P25RX is not supported by gqrx, but this will allow you to use an RTL or AirSpy type device and compare actual power units instead of the normal unit-less dBFS (decibels relative to full-scale) display. You will have to compile the source. It compiles fine on Linux. Repository is here: GitHub - bluetailtech/gqrx: Software defined radio receiver powered by GNU Radio and Qt.
Forked version of gqrx with display in dBm available
- Thread starter btt
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For a few glorious fleeting seconds, I thought I was seeing the ability to use the P25RX as an sdr coming into being. I was excited to do a head-to-head comparison to the fabled AirSpy HF+ for airband reception. 
(Please don't take this as a request, last thing I want is to add more workload to what you're already doing.)
(Please don't take this as a request, last thing I want is to add more workload to what you're already doing.)
It would be possible to add support for the P25RX-II to gqrx, but it would only allow you to visualize a single narrow band channel vs a full 5+ MHz TV channel.For a few glorious fleeting seconds, I thought I was seeing the ability to use the P25RX as an sdr coming into being. I was excited to do a head-to-head comparison to the fabled AirSpy HF+ for airband reception.
(Please don't take this as a request, last thing I want is to add more workload to what you're already doing.)
I had been wishing for ‘digital IF’ output on the P25RX-II for awhile, but didn’t want to distract with niche feature demands 😜. I’ve got a long history of adding IF taps to all my analog receivers. I think the P25RX-II with its excellent RF performance would be much better at capturing clean signal samples and developing/experimenting with demodulators than other common SDR options out there.
That said, I think I have a very unique use case—so I’l wouldn’t be picky about what software it works with (if any — a raw socket or file interface would be good enough/comfortable for me — though maybe others would prefer audio to fit in with their typical SDR virtual audio cable/audio routing setups), how debug/backdoor/unsupported it feels (though live would be strongly preferable to offline dump). Hey, if I could have anything I wanted, an always-running tap during scanning or other operation would be awesome.
That said, I do understand it might be hard to position it against say, cheap dongles with wide bandwidths. In my mind, excellent RF performance on narrowband signals is what I want (I can spend the few $ on a cheap dongle if I need bandwidth at the expense of performance), but I could see the extra feature being a positive in the minds of some, and a negative in the minds of others if doing a comparison chart between the P25RX-II and a cheap dongle. So there’s some finesse in presentation required. Developer/debug only mode or something? Or test-tool/modulation monitor style feature, vs a pan adapter?
That said, I think I have a very unique use case—so I’l wouldn’t be picky about what software it works with (if any — a raw socket or file interface would be good enough/comfortable for me — though maybe others would prefer audio to fit in with their typical SDR virtual audio cable/audio routing setups), how debug/backdoor/unsupported it feels (though live would be strongly preferable to offline dump). Hey, if I could have anything I wanted, an always-running tap during scanning or other operation would be awesome.
That said, I do understand it might be hard to position it against say, cheap dongles with wide bandwidths. In my mind, excellent RF performance on narrowband signals is what I want (I can spend the few $ on a cheap dongle if I need bandwidth at the expense of performance), but I could see the extra feature being a positive in the minds of some, and a negative in the minds of others if doing a comparison chart between the P25RX-II and a cheap dongle. So there’s some finesse in presentation required. Developer/debug only mode or something? Or test-tool/modulation monitor style feature, vs a pan adapter?
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Thanks for the comments / request. I have a simple way to do this already (for debugging), but I need to think about how to present it and make it more programmable. It is on the list!
Awesome. You posted screenshots from something awhile back (maybe?? baudline), so I figured it had happened at some point (if only during development).
There’s a whole lot about the P25RX-II that makes me want to scream “Yes! And if you’re already 90% there, what if we had XYZ too?” I also realize you’re one person, enthusiastic screams don’t write/test/support code or pay bills, and my use cases are obscure at best. Doing things like opening an API up for nerds like me could be (in the best case) very time consuming, or (in the worst case) not in your best commercial interests.
So I just want to be a tad soft about asking for features. It’s enthusiastic cheerleading, not a grumpy customer demand or dire need. It’s just refreshing to see such rapid progress, high quality, and RF performance in the same box. And not at an R9500 or G69DDCe price. Not that either of those trunk track, scan, or decode digital systems well (😜).
I feel like I bought my P25RX-II as a scanner to explore with while away/between sticking communications grade receivers, subscriber radios, and test equipment on things. What I got was a high quality tool I wasn’t even expecting.
Things like an IF-out enhance the ‘tool’ aspects of your device, but I realize it’s a scanner. So you can (and should!) prioritize appropriately.
If it were an open source project, I’d get excited about contributing. Since it’s not, all I can really do is tell friends about it and entice them to buy their own. If there’s anything else we can do, just say the word 😁.
There’s a whole lot about the P25RX-II that makes me want to scream “Yes! And if you’re already 90% there, what if we had XYZ too?” I also realize you’re one person, enthusiastic screams don’t write/test/support code or pay bills, and my use cases are obscure at best. Doing things like opening an API up for nerds like me could be (in the best case) very time consuming, or (in the worst case) not in your best commercial interests.
So I just want to be a tad soft about asking for features. It’s enthusiastic cheerleading, not a grumpy customer demand or dire need. It’s just refreshing to see such rapid progress, high quality, and RF performance in the same box. And not at an R9500 or G69DDCe price. Not that either of those trunk track, scan, or decode digital systems well (😜).
I feel like I bought my P25RX-II as a scanner to explore with while away/between sticking communications grade receivers, subscriber radios, and test equipment on things. What I got was a high quality tool I wasn’t even expecting.
Things like an IF-out enhance the ‘tool’ aspects of your device, but I realize it’s a scanner. So you can (and should!) prioritize appropriately.
If it were an open source project, I’d get excited about contributing. Since it’s not, all I can really do is tell friends about it and entice them to buy their own. If there’s anything else we can do, just say the word 😁.
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