P25RX P25 Phase 1 Receiver With Bluetooth Audio Support

btt

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AB5ID,

Thank you for the reply. Yes, I think you could put something together with a Raspberry Pi / Higher-end RTL receiver / and OP25. Based on my experience with the RTL, I don't think you would be able to achieve the same level of RF performance. I have not had a chance to test the RTL / OP25 combination in a simulcast environment. Does it perform well? Does anyone offer a complete system around the price you are looking for?

The pricing for the P25RX is currently based on low-volume cost, so I may be able to something on pricing. $150 will not be possible for me.
 

buddrousa

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And why would I want to spend $300 for a P25 Phase 1 only receiver when I can get several different options that enclude DMR P25 Phase 1 and Phase 2 scanner for the same money?
 

btt

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The current pricing is $292. It is true that it currently supports P25 Phase 1 only. DMR and Phase 2 are possibilities for the future firmware developments. Currently, Phase 2 is not operating in my receiving area. If someone can provide some good samples, I could start working on that if there is enough interest in this product.

I have had some success with DMR / Conn+. Still some minor issue with getting the wrong go-to-channel sometimes and some issues with determining correct slot to decode (get voice from both slots sometimes). I haven't touched DMR for some months. Been too busy polishing the configuration software / writing user manual / getting ready for release of the P25RX.

@buddrousa, to answer your question, Here are some features that might be appealing to some:

-Excellent performance with Simulcast system.

-Bluetooth audio streaming. Very nice for mobile operation. Plug it in, pair it with your bluetooth stereo / speaker system the first time, and go. The Bluetooth feature is also handy for a fixed location situation where you want to get the receiver / antenna up higher (on a bookshelf for example) and be able to just turn on a Bluetooth speaker when you want to listen. This is nice for people who just want to listen, but can't get around too good.

-Open-source configuration software with integrated frequency database / test functions that will run on Windows 7, 10, Linux, (possibly Mac)
-Small, rugged, portable, stand-alone aluminum enclosure with USB-C power connector.
-You would be supporting a developer from the USA who needs to start making an income again in order to pay the bills.

As I said before, I could probably lower the price a bit if there is enough interest (volume pricing).
 

buddrousa

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Good luck I just do not see it for me. Where has it tested in a true Simulcast environment and what was it tested against?
 

btt

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"Where has it tested in a true Simulcast environment and what was it tested against?"

It was developed around the Tri-cities, Wa area. See here: Benton County 800 Trunking System, Benton County, Washington - Scanner Frequencies
From RR description: "Two additional sites were added to the network, to help boost handheld coverage in fringe areas that the old radio system had coverage problems in; thus, making it a nine-site simulcast system, using linear phase modulation (CQPSK)."

During development, simulcast issues were resolved by getting testers in the 3 worst locations I could find (due to simulcast) in Pasco, Richland, and Kennewick. All of these locations were being hit by multiple towers. In the beginning, it was definitely a problem for those 3 testers. Many voice segments frames being dropped at all 3 locations. After improvements to the quadrature decoder, filters, and the multi-rate, poly-phase symbol synchronizer, all three testers ended up with excellent out-of-box performance at these locations.
 

btt

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Thanks again for the replies. Pricing has been adjusted. I hope this will generate some interest.

Here is a video demonstrating initial configuration of a control channel using the integrated frequency database.
 

MTS2000des

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I support a 15 site Astro 25 800MHz system release 7.16 (will be at 20.xx later this summer) with most talkgroups provisioned DDM, some strapped TDMA, using CQPSK-LSM. I ordered one of your units and look forward to playing with it on my system. I'd be glad to provide whatever samples needed to get TDMA working. Most of our subscribers are TDMA capable, but as is often the case, dispatch talkgroups are operating in FDMA mode due to legacy radios affiliating with our zone core and thus downgrading the talkgroup for the duration of their affiliation.
 

btt

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I support a 15 site Astro 25 800MHz system release 7.16 (will be at 20.xx later this summer) with most talkgroups provisioned DDM, some strapped TDMA, using CQPSK-LSM. I ordered one of your units and look forward to playing with it on my system. I'd be glad to provide whatever samples needed to get TDMA working. Most of our subscribers are TDMA capable, but as is often the case, dispatch talkgroups are operating in FDMA mode due to legacy radios affiliating with our zone core and thus downgrading the talkgroup for the duration of their affiliation.
MTS2000des,

Thank you! I am looking forward to getting P25 Phase 2 ready. You made my day. You have no idea how close I was to giving up on this whole thing after many months of work (and many more on a related project before that). I have also been getting DMR ready. Mostly working now. I will get an experimental version of that ready for release soon.
 

MTS2000des

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Thank you! I am looking forward to getting P25 Phase 2 ready. You made my day. You have no idea how close I was to giving up on this whole thing after many months of work (and many more on a related project before that). I have also been getting DMR ready. Mostly working now. I will get an experimental version of that ready for release soon.
I am glad folks like you are out there keeping the fire going. For what an APX RSM costs, your product has potential. I don't expect "error free" operation or perfection. It's important that folks give products like this a chance. Nothing against Uniden/Whistler (I own an SDS200 and two BCD996XTs), but the delta in price between $250-300 and $600-700 for an SDS is pretty wide. I think the form factor and build of your product is the future of scanning.

As a guy who cares and feeds for one of these multi-million buck systems for a living, I'm always tickled when enthusiasts and enterprising individuals cook up something like this that emulates what my $48,000 investment in GenWatch 3 does, and the 5-figure cost of our DiagnostX radio analyzer can and sometimes even more. Zone Watch gives me a lens into raw ATIA data, and GW3's report engine is powerful- but when I find a tool like yours I love to play. After all, many of us cut our teeth as radio enthusiasts before doing it for a living. I was around back in the days of OptoElectronics OS-456 boards in a Pro-2006 were the cat's meow. One had to REALLY work to enjoy delving into a trunking system, and unless someone worked on a system, getting info was challenging. The struggle was real!

Don't give up on your passion. When you do what you love for a living, it's like being on vacation and receiving a paycheck. I look forward to playing with your product. I have a good system to test it on. Where I live I am dead center between 4 sites and actually right along side them, if that makes sense. Raw RSSI is around -95dbM, symbol error rate on subscriber radios is low (I usually tote my agency issued APX6000 and APX8000, or Kenwood VP6430). The SDS200 has no problem with solid decode and low BER. The 996XTs are horrible OTOH.

At work our shop is in a secure location in the basement of a building. We rely on a BDA for coverage. It pumps around -75 to -90dbM of signal into the shop, obviously the closer under the antenna the better. Scanners usually have no problem as there is no delay spread as the macro is very weak (around -115dbM) without the BDA due to thick concrete walls and all the metal frame of typical urban office.
 

Falcon4

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If you wanna garner serious interest you absolutely have to make it phase 2 capable and it has to compete with op25 and raspi4. If this is a plug and play solution for people unable to do Linux and raspi4 this might seriously pick up traction.
 

btt

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Don't give up on your passion. When you do what you love for a living, it's like being on vacation and receiving a paycheck. I look forward to playing with your product. I have a good system to test it on. Where I live I am dead center between 4 sites and actually right along side them, if that makes sense. Raw RSSI is around -95dbM, symbol error rate on subscriber radios is low (I usually tote my agency issued APX6000 and APX8000, or Kenwood VP6430). The SDS200 has no problem with solid decode and low BER. The 996XTs are horrible OTOH.
Thanks again! I will get the P25RX shipped first thing tomorrow. I am looking forward to your assesment from testing in a challenging environment. I will DM later regarding the P25 P2 samples. I am committed to getting phase 2 added to the firmware. Thank you for offering to help on this!

If you wanna garner serious interest you absolutely have to make it phase 2 capable and it has to compete with op25 and raspi4. If this is a plug and play solution for people unable to do Linux and raspi4 this might seriously pick up traction.
Thank you for the reply Falcon4. I realize phase 2 is something that many people will want. I do think that I can offer something different from the op25 / raspi4 solution. The firmware for the P25RX is bare-metal and written in 'C'. (no OS interrupt jitter). The P25RX has a really good RF chain with RF shielding. The other critical part is the symbol syncronizer. This part was critical to getting good performance in our LSM area. I think another engineer who designed subscriber equipment addressed issues related this elsewhere in the "simulcast distortion" threads on this site. I'm sure we will get into that eventually.
 

MTS2000des

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I am just thrilled with the fact that SOMEONE is developing NEW hardware and software that isn't the "same old" tired design with a new front grille.
I'm putting my money where my mouth is. I bought one out of funds in my own pocket. I'm willing to give it a chance. We need to support local home grown businesses and developers who are putting effort in doing something forward thinking for their fellow radio enthusiasts. They have to eat and pay bills too. I'd much rather that profit go to feed someones' family or put their kid thru college than "Lumberg's stock go up a quarter of a point..."
 

JSTARS03

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Oh wow, this looks very interesting.
Will it do conventional P25 or just trunked P25 systems?
Can I program a trunked system in manually instead of using the database?
Any more videos of the radio in action?
Thank you
JSTARS03
 

btt

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Thanks JSTARS03,
Will it do conventional P25 or just trunked P25 systems?
As of the current version of the configuration software, it just does trunked P25 graphically. You can manually enter console commands to enable conventional mode: undocumented example:
$ is_control 0 (turn off trunking mode)
$ freq xxx.xxxxxx (set the frequency for conventional channel)
$ rssi 0 (turn off the rssi display)
$ save (save new settings to flash)

The current version of the configuration software always overrides the 'is_control' command to enable trunking after connecting to the radio. I originally had the option for conventional P25 in the graphical configuration, but decided to remove it for some reason (simplicity I think). This option could be put back in easy enough.

Can I program a trunked system in manually instead of using the database?
Yes, the general configuration page allows you to manually type in a frequency for the control channel to monitor.

Any more videos of the radio in action?
Thank you
Not yet. What would you like to see demonstrated in a video? Would it be helpful if I made a video demonstrating monitoring a conventional channel with the current software?
 

KC1UA

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Having the conventional option and eventual DMR would surely increase my interest, for what that's worth! It's great to see projects like this. Existing videos are pretty cool!
 
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JSTARS03

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Thank you for your quick response
An option in the software for conventional would be appealing especially if you have a long list of frequencies.
Would it log Radio IDs on Conventional frequencies?
Video of the logging and recording.
Have you measired sensitivity on the different bands?
Deffinately interesting
Thank you
 

btt

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I'm down to give this a shot. I just ordered one.
Thank you!

The rest of the orders shipped out today. Big thank you to all who decided to be early supporters and give this project a chance!! Thanks to MTS2000des for the first order and offering to test in an especially challenging simulcast environment!

An option in the software for conventional would be appealing especially if you have a long list of frequencies.
From responses so far, I know that I need to add the conventional support into the graphical configuration software.

I do think I need to also point out that the current firmware will monitor a single trunked system (or single P25 conventional channel as described in the previous response). There is a "roaming" mode that can be enabled. In this case, you can configure the receiver to cycle through a list of control channel frequencies (stored in flash/roaming memory) on 1) loss of signal or 2) no voice detected after xx seconds (if enabled). The no-voice-detected option is not meant to operate as a scanner, but intended to prevent "getting stuck" on an inactive control channel that you may have programmed into the roaming flash for a road-trip / travel. The user manual probably describes it better.

Video of the logging and recording.
This is on my to-do list now.

Have you measired sensitivity on the different bands?
You probably noticed I didn't specifically mention sensitivity specs directly in the user-manual. Instead, I chose to specify the first LNA characteristics which are good. Very high IP3 on all bands, level gain on all bands, and good noise figure on all bands. From my bench testing, the sensitivity is good in all the bands. I have quite a few years experience designing RF circuits and board layouts, so I don't think you will be disappointed. Almost all of the monitoring I have done with the device during development has been in the 85x MHz band. I have also been able to receive systems in the 172 MHz, 450 MHz, 770 MHz bands locally. I have not seen any 150 / 900 MHz P25 systems locally, but they should also work great.

The weakest P25 system that I can receive from my development location is a 172.xxx MHz system. This control channel usually comes in around -110, -111 dBm. I am using a TRAM mag-mount antenna for this. For an anecdotal comparison... I tried this with one of the higher-end RTL-SDR receivers (with SMA connector)/ OP25-on-PC using the same TRAM antenna and wasn't able to receive any voice at all. I did see some sparse TSBK reception. With the P25RX, this weak VHF signal fades in / out, but usually receives a pretty steady stream of TSBK. Many times the voice decodes just fine (around -106, -107 dBm I believe). Sometimes, there is loss on the voice. Note, I only did this comparison once (all in a single day) and didn't actually record the results... so don't hold me to this. I'm just trying to be transparent and give you some idea here.
 
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