P25RX P25 Phase 1/2/DMR Receiver With Bluetooth Audio Support

boy7777777777

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The only bug I’ve found so far with the newest release is the line out audio will quit after using it a while. I tried it on a new Bluetooth speaker with a line in jack and a 2020 Chevy trax line in jack. The audio quality has greatly improved over the last release. I didn’t have one instance of clipped audio. I haven’t had a chance to test it in a vehicle with an external antenna. I will try to do that in the next several days.
 
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btt

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I will test the 3.5mm line-out jack... During the entire development, I have not heard any tester mention any issues with the line out audio stopping. There have been issues with some Bluetooth speakers entering a "sleep" mode to conserve power. Could this be the issue? Did you have this issue when using the Chevy line in jack?
 

boy7777777777

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Yes it occurred on the Chevy also. I noticed it because I had another scanner running on the same system and it was staying active. Nothing was coming across the P25RX. I had it plugged in to my computer so I looked and it was receiving the signal also. It just wasn’t producing any audio. It had a good signal also. It was in the -80’s. I clicked the play audio through computer box and it produced sound through it. I could unplug the audio cable from the Chevy or the Bluetooth speaker and plug it back up and it would work for a while again. I’ll grab a different cable and make sure the one I was using wasn’t defective.
 

boy7777777777

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I changed cables and have not had the issue anymore. The cable I was using was a mono cable. Don’t know if that had anything to do with it.i switched to a stereo cable.
 
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boy7777777777

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Been testing the P25RX on the exact same equipment as my 436hp and it outperforms the 436hp on receiving and quality of decoded voice. It hasn’t missed a transmission where as the 436hp will go garbled periodically. This is tested on the AWIN system. This is using the latest firmware release. The Rssi level is -94.
 
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spacellamaman

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so i have been perusing the manual and noticed the operating range:

1.2 Operating Frequency Ranges
130 to 245 continous coverage P25 VHF
256 to 327 continous coverage P25 VHF/UHF
380 to 490 continous coverage P25 UHF
763 to 824 continous coverage P25 UHF
849 to 869 continous coverage P25 UHF
894 to 960 continous coverage P25 UHF

my question to btt here is what were the circumstances in the development process that brought about this? is it a matter of available hardware/chipsets? did you have much choice as to components that allowed you to choose the final ranges? did the hardware options not present a problem to begin with and these were just the ranges you felt appropriate etc?

20+ years ago it was common to see scanners with 380-512 coverage,in FM mode, which has always made me wonder, since at the time 380 trunked had yet to arrive and any comms in the 380-400 were likely to be AM. I assumed this was just due to component availiblity, but never had anyone to query, as I do now :)
 

btt

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Been testing the P25RX on the exact same equipment as my 436hp and it outperforms the 436hp on receiving and quality of decoded voice. It hasn’t missed a transmission where as the 436hp will go garbled periodically. This is tested on the AWIN system. This is using the latest firmware release. The Rssi level is -94.
This is great info. Thank you. There will be another release to try soon (probably today).

my question to btt here is what were the circumstances in the development process that brought about this? is it a matter of available hardware/chipsets? did you have much choice as to components that allowed you to choose the final ranges? did the hardware options not present a problem to begin with and these were just the ranges you felt appropriate etc?
Those ranges are partially determined by hardware. The frequency synthesizer divides the VCO frequency down for the various ranges. In this case, the possible divider combinations / VCO tuning range / reference frequency cause some gaps in the coverage. The other reason for gaps such as the 824-849 and 869-894 ranges is because of the rules (can't tune to those frequencies because of regulations).
 

spacellamaman

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This is great info. Thank you. There will be another release to try soon (probably today).


Those ranges are partially determined by hardware. The frequency synthesizer divides the VCO frequency down for the various ranges. In this case, the possible divider combinations / VCO tuning range / reference frequency cause some gaps in the coverage. The other reason for gaps such as the 824-849 and 869-894 ranges is because of the rules (can't tune to those frequencies because of regulations).

ok dokey,thanks for the insight. thats what i was basically what i was leaning towards. i was not surprised by:
763 to 824 continous coverage P25 UHF
849 to 869 continous coverage P25 UHF
894 to 960 continous coverage P25 UHF

and :
380 to 490 continous coverage P25 UHF
seemed about par for the course

but then i saw:
130 to 245 continous coverage P25 VHF
256 to 327 continous coverage P25 VHF/UHF

and that got me thinking, with the general trend in SDR's these days, i have come to think of most new (or near future) recievers as being nearly straight coverage capable (minus the legal mala prohibitum segments), but seeing those two bands pointed out that there are still hardware issues that are not simple or cheaply overcome. and with the inevitable gaps, also you get the inevitable coverage that you don't nessesarily have an existing need for, like the civil aviation P25 coverage in this case or the 380-400mhz FM coverage of years ago. however, the way things are going, a 190mhz P25 capable receiver may be useful in the future, assuming it isn't already :)
 

btt

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the civil aviation P25 coverage in this case or the 380-400mhz FM coverage of years ago. however, the way things are going, a 190mhz P25 capable receiver may be useful in the future, assuming it isn't already
I wouldn't be surprised about 190 MHz P25 somewhere... There may also be more demodulation/decoder options in future firmware versions. (for example, you can already listen to analog FM NB with the P25RX). This is the nice thing about SDR.

that there are still hardware issues that are not simple or cheaply overcome. and with the inevitable gaps
I wouldn't call the gaps in coverage a hardware "issue". They are very much a design decision. (high frequency VCO divided down).
 

IAmSixNine

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Looks like an amazing device. Looking forward to seeing it develop and see what new features the creator will add to it.
 
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spacellamaman

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(for example, you can already listen to analog FM NB with the P25RX). This is the nice thing about SDR.
oh cool deal, i missed that part it seems

I wouldn't call the gaps in coverage a hardware "issue". They are very much a design decision. (high frequency VCO divided down).
you'll have to excuse my 99% ignorance on the engineering aspects here, so as a design decision, in effect, while you had the flexibility to choose where the gaps would be, there was still a requirement/limitation that there had to be gaps somewhere, is that correct? "issue" was probably not the best choice of words on my part.
 

MTS2000des

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I've been using this to assist with diagnosing a BDA issue in one of my buildings. I've been using it side by side with a Signal Hound and it's got pretty damn good sensitivity, with decoding voice frames down to about -106 to -108dbm before high BER occurs. Using the stock antenna adjusted to a 5/8 wave length. Even one of the engineers from "unnamed vendor" were impressed with it. I look forward to TDMA support for P25, it will make this product even better. Duly impressed with the speed at which the proprietor is addressing issues and putting out updates.
 
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amcferrin90

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I'm just now seeing this and I love the idea. I've been looking for something small for my car not wanting to drop a wad of cash on. Then I've been really wondering why no one has put a BT chip in these scanners and eliminating wires. Congrats! I know this is still new and a work in progress. I live in Columbus OH where it seems some of the simulcast systems cause problems with the digital scanners. I'm really considering this as an option and would love to provide some feedback and diags on another tricky simulcast system.

There are so many options for this. Have you thought about using the track control buttons on your BT device to move up or down a scanlist while in TG hold? It would also be sweet if you could have a companion app that you plug your phone into the device and now you have a true 100% mobile configuration tool without the need for a computer or laptop to make changes. Now to bookmark this.
 

boy7777777777

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I’m greatly impressed with how well it works on a phase 1 non simulcast system. It decodes a weak signal very well with no dropped voice. The signal is -103dbm. Also impressed with the quick responses and firmware updates from btt. He’s has been addressing issues with a conventional P25 system I monitor and I believe he has just about totally solved the issue. I’m glad he added Bluetooth to it. I haven’t tried using it very much so can’t comment on how well it works. I would recommend it to anyone wanting to monitor a phase 1 system. It doesn’t use much cpu either. When it is decoding voice it goes from .2% to .9%. (And I have a pretty slow computer)
 
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btt

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It is time for a status update. I was shooting for having more units available for sale by now. All the parts are here to assemble more units. I am behind schedule. After selling the initial production run, I have received feedback from some P25RX users that report it does not perform well in bad simulcast areas. I am determined to get this issue resolved before selling more units. I now understand what the issue is and am working hard to get it resolved. It shouldn't take long. Hopefully, not more than a few days to address this in firmware. It will be worth the wait.

Thanks to everyone who has been providing feedback on their experiences with the device. It is appreciated.
 
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