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

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
What do the various LED colors mean for the SIG LED when the P25RX is sitting on a control channel signal?
Red
Blue
Green

On my VHF statewide trunked system, that LED is mostly RED with occasional Blue. The constellation screen shows it synced the greatest percentage of time and not synced a less amount of time even though the SIG LED is RED 90% of the time. It seems to miss a fair amount of voice grants.

On another 800 MHz system here, the SIG LED is almost always Green. I've Never seen this LED show Green on one of the VHF sites in my range.

I guess I'm confused by these colors.

My biggest issue though is with the statewide VHF P25 (non simulcast) system here, it seems the P25RX is having a tough time holding sync with any of the sites control channels within my range. I get good -77 to -88 signal levels from two sites. One site is in the 152 MHz paging band so I've tried paging notch filters to knock down the flamethrower paging transmitter signal level nearby. I must be careful though otherwise I'll also knock down the intended control channel signal I'm after.
I've also tried a step attenuator on these VHF sites but nothing really seems to help the P25RX remain synced for the VHF sites.

I've been following the P2 testing chatter and have played with those versions after seeing mention of not holding the correct site NAC.
Well, that's exactly what I was seeing with my VHF P1 sites, the NAC was jumping all over the place and voice decodes only seemed to occur when it showed the correct NAC. The SIG LED also seemed to align with the correct NAC being shown as that was the only time the SIG led was blue.
Running the latest few days of P2 test versions, the NAC is now holding steady and correct on my VHF sites but the SIG LED still changes from mostly Red to Blue and back to Red.
When I watch the console output, there is one value I see that tells me if the SIG LED will be red or blue, that's the tsbk_ps value. As long as tsbk_ps is 11 or greater, I maintain a Blue SIG led. Once tsbk_ps drops to 10 or below (including down to zero), my Sig LED turns Red.
I'm not sure what the tsbk_ps value is representing but it's definitely related when it comes to successfully monitoring these VHF P25 sites. These sites are also not simulcast but I don't think that should matter.

Is the P25RX just not up to VHF reception down around 152 MHz?

FYI - I do get great reception from these VHF P25 sites with about any scanner make or model out there.
Any Ideas anyone?

And no, I'm not knocking the P25RX in any way! I bought one as it's size is cool and I think it has great potential. I also bought it to help support btt's efforts in getting it going the way it was intended.
I don't have a lot of time as far as capturing and posting logs here but I'll do what I can when I can if asked.
The trouble system is here with VHF sites 3-16 and 3-27: Missouri Statewide Wireless Interoperable Network (MOSWIN) Trunking System, Statewide, Multi-State - Scanner Frequencies

Thanks!

Edit: Watching the tsbk_ps value, I do now see the SIG LED turn Green on at least one of my VHF P25 sites when the tsbk_ps value goes to 22 or greater only.

And of course the SIG LED also turns green when a TG with Voice is active but that occurs on any system the P25RX is receiving.

I'm running the 30-1308 version of BTConfig also.
 
Last edited:

boy7777777777

Member
Joined
Dec 16, 2011
Messages
149
Location
Arkansas
Signal quality Indicator - The signal quality indicator led is key to finding the best orientation, position, and length for the included telescopic antenna. Three colors are used to indicate signal quality (not signal strength). The indicators are as follows:
Solid green This indicates the best quality reception. When receiving from the control channel and the number of TSBK (trunking system blocks) / second is > 20 or when receiving voice and no sub-frames are dropped in a super-frame (9/9).
Solid Blue This indicates acceptable reception. When receiving from the control channel and the number of TSBK / sec is > 10 or when receiving voice, only a single sub-frame was dropped from the super-frame (8/9). An occasional blue indicator on a voice channel may result in some noticeable loss in voice quality.
Solid Red Indicates that both voice and control channels are less than optimal quality. It indicates that voice quality may be unacceptable. Note that control channel reception may still be acceptable if the number of TSBK/sec is > 5. When the TSBK/sec starts approaching 0, some conversations may be started late or missed. If TSBK/sec is 0, then the signal indicator will be off and no conversations will be heard. The signal indicator is also turned off briefly when automatically switching between the control channel and voice channels.
Blinking Green or Blue - The signal indicator will flash during voice reception when there is a pause in the communications (one side waiting for response from the other side).
Blinking Fast Red/Blue - This indicates that the Bluetooth pairing mode has been initiated and the device is currently in discovery mode looking for a Bluetooth speaker device to pair with.
Blinking Slow Red/Blue - This indicates that the Bluetooth firmware update mode has been initiated and the device is currently in bootloader mode waiting for new firmware to be uploaded. The Bluetooth firmware can only be updated with special software. Please see the Bluetooth firmware update section for more information. Press the TG button with a single-press to exit this mode. That came from the user manual.
I haven’t had any dealings with testing trunked vhf systems but I will try it tomorrow. I should be close enough to a MOSWIN site to give it a try. I have noticed that regular vhf dmr is a hair more sensitive to interference with this unit. There is not much that interferes with 700/800 MHz systems I’ve tested it on. It performs almost flawless on 700/800 MHz systems. Most of the bugs have been worked out. The lower your dbm the better the signal is that your receiving. There is a newer firmware version released today. 8-30-1405. I am able to clearly decode a 800mhz phase 1 system with -112dbm signal so the pager tower may be the issue. I’m not near as knowledgeable as most of the people on here though.
 

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
I get good -77 to -88 signal levels from two sites.
Hi kruser, Sounds like the led question was already answered, so I will just address the issue with VHF frequencies.

Also, from the user manual:

3.0 Antenna Related Information
Telescopic Antenna Included With The P25RX (omni-directional)
MANF Unbranded
Model DQZH-006
Desc: Replacement 450 mm 6 Sections Telescopic Antenna SMA male 360°
Coverage: This antenna is good for UHF reception. If you need VHF support, you will likely need to find a different antenna.

Using the wrong antenna will effectively "raise the noise floor" and lower the sensitivity. Could this be the problem? Are you using a VHF antenna?

The other thing I would take a look at is the new real-time frequency error display in the constellation in the latest versions of the software. If there is more than 100-200 Hz "Applied Frequency Correction" on average, then you should check the P25RX Configuration page to see the reference frequency matches what is on the label for your device. You can also make small adjustments to the reference frequency so that the "applied frequency correction" is close to zero while monitoring your P25 control channel.
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
Hi kruser, Sounds like the led question was already answered, so I will just address the issue with VHF frequencies.

Also, from the user manual:

3.0 Antenna Related Information
Telescopic Antenna Included With The P25RX (omni-directional)
MANF Unbranded
Model DQZH-006
Desc: Replacement 450 mm 6 Sections Telescopic Antenna SMA male 360°
Coverage: This antenna is good for UHF reception. If you need VHF support, you will likely need to find a different antenna.

Using the wrong antenna will effectively "raise the noise floor" and lower the sensitivity. Could this be the problem? Are you using a VHF antenna?

The other thing I would take a look at is the new real-time frequency error display in the constellation in the latest versions of the software. If there is more than 100-200 Hz "Applied Frequency Correction" on average, then you should check the P25RX Configuration page to see the reference frequency matches what is on the label for your device. You can also make small adjustments to the reference frequency so that the "applied frequency correction" is close to zero while monitoring your P25 control channel.
I missed the manual! Sorry about that one. I'd only seen the FAQ for some reason.

I am running outdoor antennas. Several different varieties at that. I live in a steel lined apartment much like a Faraday cage so I basically get no or very little signal indoors. Outdoor antennas up on the roof are a must. I'm on the 3rd or top floor and they let me put antennas up there.
The antennas are basically just above my head so coax runs are under 50 feet. I still use LMR400 for everything.

I am in a very high RF area which I really think is the problem here. Filtering of VHF paging is a must for almost all but the highest quality receivers.
I use PAR notch filters for the VHF paging signals which allows the GRE type scanners to handle the VHF P25 signals. Unidens are not bothered by the paging signals and of course my Icom receivers are near immune to almost all high power signals as far as overload or desense goes.
I also have a special notch filter that lowers the worst paging signal by 20dB which is enough for the AGC circuits in the cheaper radios to work again. This filter allows the radios that need filtering to still get a decent signal from the VHF P25 site

For the P25RX, I did read the FAQ and checked the freq error correction. Mine is almost right on the money with little error.
Any error is well below needing any adjustment in the BTConfig settings. And yes, BTConfig reports the same as the sticker on the P25RX!
I am using a Laird VHF antenna when working with this VHF problem but have also tried several others I have on the roof.
And as I'd said before, I did place notch filters inline to knock down the 152.240 MHz paging signals but even when the P25RX is tuned to a 154.695 MHz control channel, it will not stay synced. And that's with a -71 dBm signal level!
As I also said, I used a step attenuator and dropped the overall signal down in steps to -20 dB below normal as a test but zero help with the P25RX and the VHF P25 sites. So I don't think it's signal overload but maybe a selectivity problem as there are a ton of nearby fairly strong signals here in most bands. I live smack dab between four major hospitals so paging is my biggest issue. That and being fairly high altitude, there are several communications towers not far that serve the county.

One of the transmit sites for my counties 800 MHz P1 P25 system is maybe 1.5 miles away line of sight. It's control channel is very strong of course. About -70 dBm as well.
It broadcasts its control channel on 853.825 MHz. The P25RX will usually not go above a Red LED for this CC.
The same tower is broadcasting voice channels very close in frequency which I can only think are getting in with the control channel signal due to a selectivity issue.
A voice channel could be 853.8875 which is very close to 853.825. The tower also has a control channel for another site on 853.7875. Again, not far from 853.825.
I also can barely get sync when I try and tune the P25RX to that 853.7875 control channel.
For this particular tower site, I can get a signal indoors but it's no help with the P25RX here.

So, I'm not really sure what else I can try with the P25RX and BTConfig. It sure seems like a selectivity issue though. Especially when my other radios (over 2 dozen others) all seem to behave just fine with the sites I've been testing the P25RX with.

The site that gives me a mostly Green SIG led is a power companies 800 MHz P25 site. It's not simulcast and is about 5 miles away.
This site uses frequencies that are all 5 MHz or higher than any of the public safety sites frequencies that I have trouble with.
This site works fantastic!

One other note is when any of the troubled VHF sites do catch voice traffic and switch to the voice channel, the P25 decode quality has always been very good. This is odd as many of the voice channels are also in the 152.xxx range right with the paging crud but then some voice channels can be up in the 169.xxx MHz range also. The clear sounding voice channels in the 152.xxx range should also suffer from the nearby paging signals if my selectivity theory is true. So I really don't get it!

Is there a way the RF Gain can be manually adjusted through the console or perhaps the AGC action?
If so, maybe I can try messing with those areas and see if I can improve my VHF problem.

I can also receive more distant sites that don't have control channels in that 853.xxx MHz block. Those sites and systems usually work well plus give me a nice and steady Green SIG indicator!

Any Ideas of what I can do to try and improve things here?

Thanks Again!
 

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
Hi kruser,

Hope I didn't insult you with the question about the antenna. I was just checking to make sure that wasn't the issue. Obviously it isn't.

The LNA in the P25RX has an OIP3 of > +40 dBm. The LNA is a high quality, low distortion amp. The front-end contains limiters. It will demodulate FM fine up to +22 dBm (max output on my HP signal generator).

I recently updated the user manual with blocking specs:

74 dB @ 10 MHz offset
65 dB @ 2 MHz offset
59 dB @ 1 MHz
Adjacent 26 dB (12.5 kHz offset)

As you can see from the specs, that close-in selectivity is not as good as a super-het with a 45 MHz Crystal IF filter, but is also not bad either. By the time you get out 2 MHz offset, it is very good. The receiver utilizes a low-IF followed by a switched-cap low-pass filter. In the cases where you have an active adjacent channel, are they reaching signal levels greater than 26 dB above the signal you are trying to receive?

There are no 15x.xxx MHz systems in my area, so I can't say with 100% confidence that there is no issue at those frequencies. I am going to do some tests with the signal generator tomorrow and see if I can detect an issue. Can you give me a list of exact frequencies that I should specifically check?

Any chance you could post a video of the "Constellation View" with the P25RX in operation at the VHF frequencies you are having trouble with?
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
No insult taken! I'm actually having a lot of fun trying to get this thing working.
Believe me, this is not the first time I've had issues here with the high rf levels around here.

As to your question about high signal levels near the receive frequency. Nothing would come close to the 26 dB figure you mentioned. If anything, adjacent signals will probably be mostly equal to those I'm tuning.
Since my last post, I tuned a control channel for a distant site that's part of the county 800 system here that I have troubles with. This distant site also uses frequencies adjacent to the much stronger control channels that give me problems. To my surprise, I was able to copy this distant site without any issues. The SIG led remained green the entire time it was sitting on an idle control channel as well. I then tried the other somewhat distant site that's a part of this county system and again, it came in just fine and also with a solid green SIG led!
This second site also has a very close adjacent control channel frequency so I'm more puzzled now than I was before. I went back to trying attenuation of the two control channels that give me mostly red SIG color. Attenuation does not seem to help. I can watch the signal level rise and fall as I alter the atten level on the BTConfig console or the constellation screen but nothing I do will clean up the signal enough to get at least mostly blue SIG indication. I can pretty much forget about a green SIG indication for these two local control channels!
The above is all on a local tri-county 800 MHz simulcast P25 system. It has five simulcast sites and I can receive 4 of them with about any P25 radio. The stumper is why the P25RX does not like the two strongest control channel signals from the two nearest sites yet it works great on the two more distant sites!
The two distant sites yield an -95 dBm signal level on average when I look at the P25RX stats. Those sites receive great and with a solid green SIG led. The two much closer sites yield -71 and -82 dBm respectively yet they usually only decode the control channels with a red SIG level.
That system is here: St. Louis Area Trunked Emergency Radio (SLATER) Trunking System, St Louis Metro Area, Multi-State - Scanner Frequencies
Sites 1-1 and 1-2 are the strong sites that give a red SIG led indication on the control channels of 853.825 and 853.7875
Sites 1-3 and 1-4 are the two more distant sites that give a nice solid green SIG led from their control channels! I can't get 1-5 as its antennas point away from me.

The more I messed with the 800 MHz sites above, the more I realize how much they behave like the two 15x.xxx MHz sites I'm also having the same basic issue with. Maybe that's just coincidence but it seems odd!

The two VHF sites are here: Missouri Statewide Wireless Interoperable Network (MOSWIN) Trunking System, Statewide, Multi-State - Scanner Frequencies
Sites 3-16 and 3-27. The control channels are 154.695 and 152.600 respectively. 154.695 is nearer me but is the worst for seeing much above a red led sig indication. It gives me a -74 dBm signal level. The other slightly further site on 152.600 gives me maybe 50% red/50% blue SIG hits with a -80 dBm level but yields a better SIG indication.
This puzzles me as the 152.x MHz site should be worse being right next to the 152.240 paging powerhouse that can hit here with -50 dBm levels! But, the 154.695 control channel without much adjacent channel activity is worse.
It seems more like an overload problem of some type the more I look at what works well and what has problems.
My original theory of selectivity was probably wrong. Your numbers show that plus what my newest findings are showing me the same and selectivity should not really be a concern.

I have a fairly large array of various low and high pass as well as bandstop filters here.
I tried a bandpass filter for 850 to 869 on the problem 853 MHz local control channels but no help. That filter has a sharp cutoff above and below it limits and reduces everything outside by -40 dB so it does not appear to be anything way out of band causing issues.
I then tried various filters while watching the 152 and 154 MHz control channels. I tried high pass that cuts everything below 148 MHz. No help.
I tried low pass that cuts everything above 600 MHz and still no help.
The only thing I could not filter is the area above 160 MHz to 600 MHz. I thought I had a filter for that range but no luck finding it if I do!

One thing I do see is a fair amount of frequency jumping around on the Frequency Error Estimate line in the Constellation View when tuned to the 154.695 control channel. It can jump around from say -20 Hz up to +50 Hz or more within seconds. I'm not sure that's bad or not.
The Applied Frequency Correction never goes greater than +35 Hz or so regardless what the error estimate is showing.

I'll try and figure out how to grab a live image of the constellation view and upload it somewhere. It may take me a while as I don't think I've ever captured video before in the past nearly 40 years!

Sorry for the long post but I wanted to try and explain what I've been seeing.

One other thing is with the NAC shown. When I first noticed the issues with the VHF sites, the NAC for either site was jumping all over the place. It would show correctly for a bit and then go crazy again.
I'd been following the posts about getting Phase 2 going and in one of your posts, you mentioned possibly fixing the NAC issue but for a P2 site. I gave that version a try and sure enough, it did fix the NAC problem with my VHF sites as well!

Thanks!
 
  • Like
Reactions: btt

boy7777777777

Member
Joined
Dec 16, 2011
Messages
149
Location
Arkansas
I have noticed with this newest firmware release it will not decode DMR. I am monitoring a VHF DMR conventional repeater site. It is a very strong signal -71 DBM. It will only catch parts of sentences.
 
Last edited:
  • Like
Reactions: btt

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
I'm thinking this could have something to do with frequency error correction at VHF frequencies. It may also be that the frequency correction is drifting off in conventional mode when there is no carrier.

New version available 31_0655. This version does not do frequency error correction when in conventional mode ( is_control = 0) or if you disable it with a new command:

$ ferr_en 0
$ save

This will version will reset the configuration because of the new command added.

If you know the reference frequency is already very good (applied frequency correction is usually close to zero), then disabling the frequency error correction will be fine if temperature doesn't change too much. Can you please give this a try and see if it helps?

[edit]
If you disable frequency correction, then you might want to also change the "frequency offset" to zero in the P25RX Config tab and cycle power. This is the applied frequency correction on power-up. The reference is a TCXO (temperature compensated oscillator).
 
Last edited:

Mike_G_D

Member
Joined
Dec 19, 2002
Messages
1,091
Location
Vista, CA
First, I'll update a little on my own observations with the latest (30_1405 and 31_0655) versions:

Pretty good for the most part. I still am getting those odd little "peak dropouts" and slight distortion on the audio peaks. This is NOT through the PC audio this is through the Line Output. I tried adjusting the line out level way down but that did not fix the issue. It sounds very similar to analog FM when the modulation frequency deviation is outside the IF and discriminator bandwidth with the squelch set (distortion and then complete audio dropout at the peaks).

The above is pretty minor, though overall. Just noticeable and I can definitely tell when compared with audio from my scanner demodulating the same signal.

Seems like it really hasn't changed much if at all over the last three or four version changes, just in case that information helps at all.

Audio seemed the cleanest back with a version that, as I recall, didn't use the talk group delay correctly - it just hung on the voice frequency for a set time after traffic ended rather than following the talk group conversation. That seems to jive with ptt's earlier posts concerning the AGC action versus

But, apart from the above, for the most part, audio is very good and it seems to track the talk groups well and delay seems good. I have not experienced the bad mixed up talk group/talk group "bleedthrough" issues that plagued me so much last week. So that is a big plus in my book!

Now, to address kruser's observations:

Before all of the P2 experiments began on my end, I was starting to write up a series of notes concerning my observations with the overall RF performance of the P25RX. I have limited time to work on this and have very limited internet connectivity so must apologize.

One thing I have been wanting to bring up but keeps getting pushed back due to other more pressing issues is that I noticed an unusually high amount of broadband noise within the VHF-HI band on the ground or shield of the P25RX. This was very early on in my testing of the device. What I noticed was that when I used the included telescopic antenna which, of course, has no ground plane outside of the metal case of the P25RX I did not have a noticeably bad increase in VHF broadband noise on my other receivers but when I connected the receiver to another port on my splitter which my other receivers are connected to the noise went up substantially on all of my other receivers. I have an ICOM R7000 which has an analog S-meter and it bumped up several S units when the P25RX was connected and powered up within the VHF-Hi band. I then tried the small 800MHz antenna with the mag mount that I received with the P25RX - still a high noise floor rise. So then I went back to the back-of-set telescopic antenna; result - drastic reduction in noise. That's when I started thinking the ground or shield was the radiating source. So I gripped the shield of the SMA connector attaching the antenna to the P25RX tightly with my fingers thereby coupling my hand and body to the ground plane and observed a significant rise in the noise floor on my other radios, not as much as when using the 800MHz mag mount or attaching directly to the splitter but significant enough that I was fairly sure the SMA shield (RF ground) of the P25RX was the noise source or at least the prime radiator. The little 800MHz mag mount doesn't radiate to well at VHF-HI frequencies, obviously, but the outer shield of the thin coax it is attached to is plenty long enough to radiate at those frequencies. The back-of-set antenna provides virtually nothing in the way of SMA ground plane to radiate effectively at VHF-HI frequencies so hence less noticeable noise.

Now, that's where I stopped. I have no access to decent test equipment to go much further and I had to move on to other things anyway at the time. For a long time, I just used the little back-of-set telescopic fully collapsed and put the whole unit up as high as I could for subsequent testing so that it didn't radiate so much noise to the other radios. I was mostly interested in the 800MHz trunking use for the P25RX anyway.

The only other relevant subsequent related test I did was try a VHF-FM conventional test wherein I tried to receive a local NOAA weather broadcast. I found I could not using the back-of-set antenna fully raised no matter where I held the unit (normal scanner with a small antenna or ducky usually will get this signal fine) and squelch had to be set quite high at -80 dBm or so which I thought seemed pretty high (on a random VHF-HI frequency with no signal).

Now, I have to say that my setup is not VHF-friendly! I am limited to an inside apartment setup with a small antenna that is really only efficient from about 200MHz and up. I have an in-line amp that goes between the antenna and a 8-way mini-circuits splitter. The amp is just there to overcome the line and splitter loss and maybe add a tiny bit of extra gain. I have a number of low dB attenuators in-line to balance the gain of the amp so as to just be enough to overcome line and splitter loss plus a little more.

I have a lot of local noise sources in and around this setup that raise the noise floor a lot anyway in the VHF bands but what I saw from the P25RX is over and above my local "norm". Still, there could certainly be other ground-related issues that might be contributing to the apparent high noise floor when the P25RX is connected. I also have an audio cable connected to the Line Out of the P25RX going to an audio mixer. So there are a lot of "ground loops" that might be possible from an RF standpoint.

Currently, the P25RX is again connected to the splitter because I needed to compare it as closely as possible to my scanner and wanted to use the same antenna system. But now I see only about 1 S-unit increase in noise on VHF whereas before I saw something like 5 S-units or so increase. So, unsure what to make of that - maybe some clock change or some digital timing changes stemming from the recent firmware changes altered things. But, that's an improvement, so...

I can now receive the weather signal but it is distorted. And the FM conventional settings using the console commands seem a little flakey as they seem to randomly revert to going back to the 800MHz control channel after a short time (followed procedure outlined on the BlueTail website).

So, I don't know if broadband noise in the high band might be a factor in kruser's case - with his outside antenna setup I would think maybe not unless the local noise in the P25RX is causing issues internally.

-Mike
 

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
The noise floor on the P25RX is actually about as good as it gets. I can receive voice reliably below -120 dBm. This would not be possible without the incredible low internal noise. I do have several spectrum analyzers. If you look at the specs in manual, you will see that the only emission I could even measure was the VCO above 3 GHz around -86 dBm. You won't find many receivers with these kind of specs.

On another note,

I have been working on a less aggressive algorithm for the frequency error correction to see if that might help with the issues kruser and boy7777777 are having at VHF frequencies. I'm going to hold off putting it on the web site until I hear back if disabling frequency error correction helped with issues.
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
So, I don't know if broadband noise in the high band might be a factor in kruser's case - with his outside antenna setup I would think maybe not unless the local noise in the P25RX is causing issues internally.

-Mike
Thanks for all your great notes!
I've not had time to test much but with your info I will have plenty to look for.

I did try version 31_0655 and the switches btt mentioned but cannot say any of it made a difference with my VHF issues.
I've since defaulted the P25RX but left 31_0655 on it for more testing later today.

I am interested in the high noise floors you observed on your R7000. I also have the R7000 and R9000 but I was not watching them. I will do so when I have time for more testing.

All good info!
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
The noise floor on the P25RX is actually about as good as it gets. I can receive voice reliably below -120 dBm. This would not be possible without the incredible low internal noise. I do have several spectrum analyzers. If you look at the specs in manual, you will see that the only emission I could even measure was the VCO above 3 GHz around -86 dBm. You won't find many receivers with these kind of specs.

On another note,

I have been working on a less aggressive algorithm for the frequency error correction to see if that might help with the issues kruser and boy7777777 are having at VHF frequencies. I'm going to hold off putting it on the web site until I hear back if disabling frequency error correction helped with issues.
I did try disabling frequency error correction but did not see any improvements at all regarding getting a decent blue or green SIG indication.
I also tried moving the reference freq up and down in increments of 10 until I lost lock all together in both directions from default. The default of 39999905 (for my P25RX) seemed to be about in the middle so I set it back there.

Lot's of fun experimenting but no luck yet!

Regarding the low noise floor, I did indeed notice that. For the better systems here, I can reliably decode them down to -115 dBm at least so that part seems great. This was with 800 MHz signals though. I did not look at VHF yet.

I was looking over the datasheet for the RF chip.
I saw reference about the low VHF ranges and a note to contact TI for use of this chip in some of these low VHF ranges. Of note was the mention of the range I'm having issues with! I'm not sure if that means anything as I did not really read into it any further but it may be worth looking at in the full datasheet.
I attached just page 8 from the datasheet. Look at section 4.5 RF Characteristics under the Frequency Bands Parameters line for 136.7 to 160 MHz line and you will see the note: "Contact TI for more information about the use of these frequency bands." In that section, the range from 205 to 240 MHz is also included.

I'm not sure what TI will suggest regarding that notation but it must mean something.
Maybe worth a read and contacting them if you did not catch that before.

Anyway, just wanted to say that I did try messing with your suggestion with Ver 31_0655 but did not really find any significant change.
I also wanted to point out what I'd read in the datasheet for the RF chip. I hope I looked at the right datasheet!!

Thanks!
 

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
I attached just page 8 from the datasheet. Look at section 4.5 RF Characteristics under the Frequency Bands Parameters line for 136.7 to 160 MHz line and you will see the note: "Contact TI for more information about the use of these frequency bands." In that section, the range from 205 to 240 MHz is also included.
This is most likely related to an issue that came up in early versions of the silicon. I solved that issue 8 years ago for an industrial, high-power VHF design I did back then. We sold hundreds if not thousands of them, so I doubt there are issues related to that. There was a VHF pre-selection filter on that design, so there is that difference. The reason I doubt that is the issue at this point is because you tried the bandpass filters without solving it. I tested your problem frequency today with a signal generator. I didn't notice any audible issues with the demod from -110 to +22 dBm, but as I mentioned I do not have a local cc at that frequency range to test. Can you at least give a representative screenshot of the constellation view when on the control channel with issues?

This isn't really the kind of discussion I was hoping to have in a public forum. I haven't had a single customer since Phase II TDMA support was added. I was hoping that would turn things around for sales.
 

btt

Member
Premium Subscriber
Joined
Mar 11, 2020
Messages
250
Location
Wa State
@kruser,

I apologize for my previous response. I realize that you are just trying to help identify why you are having issues when you posted about the datasheet. I am just a bit frustrated lately. I am starting to realize that this small business that I am trying to start is probably not going to make it. This is the second time in my life that I walked away from a big paycheck, spent all my savings and retirement on trying to get a business going. It did seem this project was going to be enough to at least make a minimum-wage type income in the beginning. Only 2 units sold since 8/3. So, DMR and Phase II TDMA support were not the issues holding back sales.

Anyway, please continue to post any kind of issues including silicon errata that you dig up. I will do my best to address the issues while I can full-time. I will also continue to try and support this project after-hours when I inevitably have to return to working for someone else.
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
This isn't really the kind of discussion I was hoping to have in a public forum. I haven't had a single customer since Phase II TDMA support was added. I was hoping that would turn things around for sales.
Ha, I don't want to jinx any sales! I think it's a great product with a lot of potential.
I saw I forgot to add that datasheet page anyway but it sounds like you are on it already.

I'll do what I can for grabbing a constellation view screenshot and get that to you.
To my eyes, the constellation view looks no different than the 800 MHz sites that work perfect if my word helps you until I can figure out how to capture a live moving image of the constellation window.

I've also not noticed any stray or odd rises in the noise floor in any other radios when the P25RX is hooked up. I was not really looking for that but it is something I'd usually notice regardless. I still plan on doing some testing in that area though.

Thanks for your suggestions thus far!
 

KC1UA

Scan New England Janitor/Maintenance
Database Admin
Joined
Oct 27, 2002
Messages
1,685
Location
Marstons Mills, Cape Cod, Massachusetts
I wonder how many people are even aware that phase 2 and DMR are now available for this device. The reason I say that is that this thread has become 18 pages worth and the intro of both protocols really didn't arrive for several pages in.

Maybe a new thread that P25RX now offers Phase 2/DMR Support could spark some interest. I know if there is a thread that I am not overly invested in I stop viewing it after a while. I'm sure I'm not the only one.

Just a thought, and I may be way off the mark, but who knows?
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,008
Location
West St Louis Cnty, MO
Maybe a new thread that P25RX now offers Phase 2/DMR Support could spark some interest. I know if there is a thread that I am not overly invested in I stop viewing it after a while. I'm sure I'm not the only one.

Just a thought, and I may be way off the mark, but who knows?
I think that's a good idea for the OP.
I've read a few other threads in other forums with mention of the P25RX and they usually ended when lack of P25 P2 support was mentioned.
I did see someone mention P2 support was in the works in another forum very recently but I can't recall which.

So yes, I'd say a new P2 support announcement is in order.
 

Davrs

Newbie
Joined
Aug 18, 2020
Messages
1
I wonder how many people are even aware that phase 2 and DMR are now available for this device. The reason I say that is that this thread has become 18 pages worth and the intro of both protocols really didn't arrive for several pages in.

Maybe a new thread that P25RX now offers Phase 2/DMR Support could spark some interest. I know if there is a thread that I am not overly invested in I stop viewing it after a while. I'm sure I'm not the only one.

Just a thought, and I may be way off the mark, but who knows?
Totally agree with that. I almost missed that in the long thread.
 
  • Like
Reactions: btt
Top