P25 Digital Repeater using Motorola Radios
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P25 Digital Repeater using Motorola Radios
UPDATE:
It is not necessary to do internal mods to Motorola radios to pass P25 data. I discovered that you can use Pin 5 (Flat Tx audio) instead of adding 10k resistor and injecting audio at TXa test point. You can use Maxtrac, CM SERIES, CDM SERIES,SM SERIES, RADIUS SERIES for all radios. Use pin 11 (discriminator) with a 10-20K variable resistor in line between TX and RX you must ground the unused pin of the resistor (You can use pin 7). I am working on a data validation circuit that will allow for only P25 data to be passed thru the repeater if so desired.
PINOUTS
PROGRAM RX RADIO FOR PIN 8 ACTIVE LOW
ALSO PLACE JU551 TO A
RX RADIO TX RADIO
PIN 8 COR DETECT PIN 3 PUSH TO TALK
PIN 7 GND PIN 7 GND
PIN 11 DISCRIMINATOR /\/\/\10-20K VR PIN 5 FLAT TX AUDIO
ADJUST VR for 2.9 to 3.5 Khz of DATA.
It is not necessary to do internal mods to Motorola radios to pass P25 data. I discovered that you can use Pin 5 (Flat Tx audio) instead of adding 10k resistor and injecting audio at TXa test point. You can use Maxtrac, CM SERIES, CDM SERIES,SM SERIES, RADIUS SERIES for all radios. Use pin 11 (discriminator) with a 10-20K variable resistor in line between TX and RX you must ground the unused pin of the resistor (You can use pin 7). I am working on a data validation circuit that will allow for only P25 data to be passed thru the repeater if so desired.
PINOUTS
PROGRAM RX RADIO FOR PIN 8 ACTIVE LOW
ALSO PLACE JU551 TO A
RX RADIO TX RADIO
PIN 8 COR DETECT PIN 3 PUSH TO TALK
PIN 7 GND PIN 7 GND
PIN 11 DISCRIMINATOR /\/\/\10-20K VR PIN 5 FLAT TX AUDIO
ADJUST VR for 2.9 to 3.5 Khz of DATA.
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The VHF Maxtrac to UHF Maxtrac had a problem with one of the receivers inverting the data. (Can't remember which off the top of my head)
I had to either modify the "inverting" receiver, or change where the audio from the Rx's Disc entered the TX Radio.
Just an FYI
tpg
I had to either modify the "inverting" receiver, or change where the audio from the Rx's Disc entered the TX Radio.
Just an FYI
tpg
Experienced Provider of Useless Information
Have you used one of these before or done a back to back comparison?
P25 error detection is pretty damn robust, if a repeater is getting a noisy signal the total BER *should* be the same as if it was working in simplex mode (a la the above repeater). A Quantar can't magically correct uncorrectable errors.
Just interested in how well these things work
P25 error detection is pretty damn robust, if a repeater is getting a noisy signal the total BER *should* be the same as if it was working in simplex mode (a la the above repeater). A Quantar can't magically correct uncorrectable errors.
Just interested in how well these things work
Not with P25 specifically, but I've done the same thing with other digital systems.
A Quantar can correct quite a few errors - that's what Forward Error Correction codes are for. When it receives a signal, it will do this, and generate a brand new, clean signal.
This thing, on the other hand, will add noise to what may already be a rather crappy signal if you're trying to hit the machine from the fringes. The signal's journey from the repeater to the receiving radio will then also result in futher deterioration to what may already be a bad signal - whereas from a Quantar, you'd be listening to a fresh, clean, error corrected signal.
A Quantar can correct quite a few errors - that's what Forward Error Correction codes are for. When it receives a signal, it will do this, and generate a brand new, clean signal.
This thing, on the other hand, will add noise to what may already be a rather crappy signal if you're trying to hit the machine from the fringes. The signal's journey from the repeater to the receiving radio will then also result in futher deterioration to what may already be a bad signal - whereas from a Quantar, you'd be listening to a fresh, clean, error corrected signal.
OK, I see what your saying..
I think it would still make for an interesting project though, if it can get 90% of the performance for 10-20% of the cost then id call it a success, especially if you can use DTMF tones to switch a PL on and off and use it as a conventional HAM repeater too.
Of course, nothing beat a Quantar!
Cheers,
Matt
I think it would still make for an interesting project though, if it can get 90% of the performance for 10-20% of the cost then id call it a success, especially if you can use DTMF tones to switch a PL on and off and use it as a conventional HAM repeater too.
Of course, nothing beat a Quantar!
Cheers,
Matt
BER, while a useful end-to-end metric of a signal, is NOT the appropriate measurement to be making here - modulation fidelity is.MattSR wrote:P25 error detection is pretty damn robust, if a repeater is getting a noisy signal the total BER *should* be the same as if it was working in simplex mode (a la the above repeater).
Yes - a high BER will cause your signal to fall on its face. But what causes a high BER? It is the radio's inability to distinguish between symbols. And what is the measurement of how "hard" symbols are to distinguish? Modulation fidelity. You will see pretty much the same BER for a 10% modulation fidelity error as you will for a 0.7% error, but if you see a 10% MFE you can know the system is NOT performing well - you have lost most of your margin for decode, and any increase at all in the distortion of the signal will start causing errors.
Think of it as the difference between SINAD and intelligibility - you can have a 20 dB SINAD or a 12 dB SINAD, and still understand what the other guy is saying 100% - but if you are at a 12 dB SINAD coming out of the repeater, any additional noise is going to start causing a whole lot of "What did you say? Say again?" traffic.
The advantage of regenerating the digital signal, even if you don't apply the forward error correction at that point, is that you can go from a 10% MFE to a 0.7% MFE, and thus improve the odds of correctly decoding the signal.
AND, if you then apply the FEC to the signal, you can further clean it up, so that you can once again pick up bit errors without the radio being unable to decode.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
Hi folks,
I've two GM950 model M08RHH4AN4AN connected together with :
RX pin 8 (CSQ detect - low active) =>>> TX pin 3 (PTT - low active)
RX pin 11 (RX Discri) =>>> TX pin 5 (Flat Tx) trough a 22 k variable resistor
RX pin 7 (GND) =>>> TX pin7 (GND)
I'm using two XTS3000 model H09RDH9PW7BN host R07.09.02 DSP 08.02.04 flashcode 500008-000000-1. Those two radios are configured in 2,5 kHz deviation in ASTRO mixed mode C4FM, low power for lab testing.
The repeater is on the table for lab with a dummy load for TX (433.400 Mhz and no antenna for RX (439.800 MHz).
1) in analog mode, the repeater is working fine. The pot is able to adjust the tx audio.
2) in astro mode, i've got nothing
As i ask before, is it a limitation using a 12,5 kHz TX for repeating ASTRO P25 ?
Pierre
I've two GM950 model M08RHH4AN4AN connected together with :
RX pin 8 (CSQ detect - low active) =>>> TX pin 3 (PTT - low active)
RX pin 11 (RX Discri) =>>> TX pin 5 (Flat Tx) trough a 22 k variable resistor
RX pin 7 (GND) =>>> TX pin7 (GND)
I'm using two XTS3000 model H09RDH9PW7BN host R07.09.02 DSP 08.02.04 flashcode 500008-000000-1. Those two radios are configured in 2,5 kHz deviation in ASTRO mixed mode C4FM, low power for lab testing.
The repeater is on the table for lab with a dummy load for TX (433.400 Mhz and no antenna for RX (439.800 MHz).
1) in analog mode, the repeater is working fine. The pot is able to adjust the tx audio.
2) in astro mode, i've got nothing
As i ask before, is it a limitation using a 12,5 kHz TX for repeating ASTRO P25 ?
Pierre
Make sure that the audio path has as flat a passband response as possible - take the audio directly from the detector, and route it as directly to the modulator as possible.
Remember that many radios have either a C-weighted audio response, or some other bandpass response. *ANY* non-flat frequency response will KILL the APCO-25 waveform - drive the intersymbol interference through the roof, and make your modulation fidelity error HUGE.
Can you get access to something that can measure P25 modulation fidelity (and it's pretty obvious what I'd recommend...) - if you can actually get something that can show you the eye diagram or modulation fidelity that would really help you identify the problem.
Remember that many radios have either a C-weighted audio response, or some other bandpass response. *ANY* non-flat frequency response will KILL the APCO-25 waveform - drive the intersymbol interference through the roof, and make your modulation fidelity error HUGE.
Can you get access to something that can measure P25 modulation fidelity (and it's pretty obvious what I'd recommend...) - if you can actually get something that can show you the eye diagram or modulation fidelity that would really help you identify the problem.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
it work's !!!
I've change the RX radio for a 25 kHz spacing channel capable, and it's works very fine
We've looked at the TX deviation to be in the limit of 3 kHz.
So i anderstand now that you need a pair of 25 kHz radio to make the P25 repeater become a true story
many thank's to all of you.
Now we have the first P25 repeater in Paris.
Pierre
I've change the RX radio for a 25 kHz spacing channel capable, and it's works very fine
We've looked at the TX deviation to be in the limit of 3 kHz.
So i anderstand now that you need a pair of 25 kHz radio to make the P25 repeater become a true story
many thank's to all of you.
Now we have the first P25 repeater in Paris.
Pierre
P25 ADP AlgoID
Hi guys,
Does anyone with a P25 service monitor here know the AlgoID for ADP? Ive discovered some common algos in P25 training docs and whatnot, but the value for ADP escapes me, and I dont have a 2975 to check it with
Discovered some more AlgIDs (but not ADP sadly)
Heres the values that I have found (from publicly available docs on the net)
0x00 Accordion 1.3
0x01 BATON (Auto even)
0x02 Firefly
0x03 Mayfly
0x04 Saville
0x41 BATON (Auto Odd)
0x80 Clear
0x81 DES-OFB
0x82 2 key Triple DES
0x83 3 key Triple DES
0x84 AES-256
0x9F DES-XL
0xA0 DVI-XL
0xA1 DVP-XL
Does anyone with a P25 service monitor here know the AlgoID for ADP? Ive discovered some common algos in P25 training docs and whatnot, but the value for ADP escapes me, and I dont have a 2975 to check it with
Discovered some more AlgIDs (but not ADP sadly)
Heres the values that I have found (from publicly available docs on the net)
0x00 Accordion 1.3
0x01 BATON (Auto even)
0x02 Firefly
0x03 Mayfly
0x04 Saville
0x41 BATON (Auto Odd)
0x80 Clear
0x81 DES-OFB
0x82 2 key Triple DES
0x83 3 key Triple DES
0x84 AES-256
0x9F DES-XL
0xA0 DVI-XL
0xA1 DVP-XL
Re:
Hi wowbagger,
Its only taken me three years to digest your post - but yes you are quite right, I've learned a fair bit since I made my original post, and thanks for the explanation - it has pointed me i the right direction
Cheers,
Matt
Its only taken me three years to digest your post - but yes you are quite right, I've learned a fair bit since I made my original post, and thanks for the explanation - it has pointed me i the right direction
Cheers,
Matt
Wowbagger wrote:BER, while a useful end-to-end metric of a signal, is NOT the appropriate measurement to be making here - modulation fidelity is.MattSR wrote:P25 error detection is pretty damn robust, if a repeater is getting a noisy signal the total BER *should* be the same as if it was working in simplex mode (a la the above repeater).
Yes - a high BER will cause your signal to fall on its face. But what causes a high BER? It is the radio's inability to distinguish between symbols. And what is the measurement of how "hard" symbols are to distinguish? Modulation fidelity. You will see pretty much the same BER for a 10% modulation fidelity error as you will for a 0.7% error, but if you see a 10% MFE you can know the system is NOT performing well - you have lost most of your margin for decode, and any increase at all in the distortion of the signal will start causing errors.
Think of it as the difference between SINAD and intelligibility - you can have a 20 dB SINAD or a 12 dB SINAD, and still understand what the other guy is saying 100% - but if you are at a 12 dB SINAD coming out of the repeater, any additional noise is going to start causing a whole lot of "What did you say? Say again?" traffic.
The advantage of regenerating the digital signal, even if you don't apply the forward error correction at that point, is that you can go from a 10% MFE to a 0.7% MFE, and thus improve the odds of correctly decoding the signal.
AND, if you then apply the FEC to the signal, you can further clean it up, so that you can once again pick up bit errors without the radio being unable to decode.
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Re: P25 Digital Repeater using Motorola Radios
Sorry to digg up an old thread, but what are people's recommendations on UHF versions that would do this say around the 420-450 area
Thanks
Thanks
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Re: P25 Digital Repeater using Motorola Radios
The $64,000 question was "What's the basis for your P25 validation circuit?". Well, perhaps the answer might be found here:
http://nicta.com.au/__data/assets/pdf_f ... ware_1.pdf
Now before anyone starts going on about DVSI (and other's) patents notice that this project was to convert P25 RF received off air to digital data displayed on PC and it wasn't intended as a saleable product.
Well it turns out that this project was based on the GNUradio free software development signal processing toolkit. You can do further reading here:
http://sedition.org.au/op25/wiki/WikiStart
and
http://gnuradio.org/trac/wiki
plus a cool 4FSK software demod plug in from:
http://radiorausch.googlepages.com/Gnur ... elFSK.html
BUT and it's a big BUT, this is a major major project with good C++ skills required. It is hardly ‘batteries not included’, it’s not ‘some assembly required’, and it’s certainly not 'plug and play' like Unitrunker.
Well actually a whole lot of assembly is required and while it looks like the transmit functions are still a bit primitive, these Australians look pretty serious.
Note also that the implementation is done via sampling either the RF or IF rather than by means of a discriminator tap (although that is certainly possible). The whole software-defined radio thing looks a bit overly complex and expensive when using the typical USRP front end when most people here would be able to lay their hands on suitable RF decks but Max KA1RBI has done a simple 455 kHz to sound card IF design is here:
http://www.lightlink.com/mhp/iq/
So the whole "P25 validation circuit" is going to look like a small PC server.
Oh, and here's the thing - you're not going to be trying to sell this as a commercial product because while you don't need an IMBE decoder for a repeater you will still be using all sorts of IP that belongs to others...
http://nicta.com.au/__data/assets/pdf_f ... ware_1.pdf
Now before anyone starts going on about DVSI (and other's) patents notice that this project was to convert P25 RF received off air to digital data displayed on PC and it wasn't intended as a saleable product.
Well it turns out that this project was based on the GNUradio free software development signal processing toolkit. You can do further reading here:
http://sedition.org.au/op25/wiki/WikiStart
and
http://gnuradio.org/trac/wiki
plus a cool 4FSK software demod plug in from:
http://radiorausch.googlepages.com/Gnur ... elFSK.html
BUT and it's a big BUT, this is a major major project with good C++ skills required. It is hardly ‘batteries not included’, it’s not ‘some assembly required’, and it’s certainly not 'plug and play' like Unitrunker.
Well actually a whole lot of assembly is required and while it looks like the transmit functions are still a bit primitive, these Australians look pretty serious.
Note also that the implementation is done via sampling either the RF or IF rather than by means of a discriminator tap (although that is certainly possible). The whole software-defined radio thing looks a bit overly complex and expensive when using the typical USRP front end when most people here would be able to lay their hands on suitable RF decks but Max KA1RBI has done a simple 455 kHz to sound card IF design is here:
http://www.lightlink.com/mhp/iq/
So the whole "P25 validation circuit" is going to look like a small PC server.
Oh, and here's the thing - you're not going to be trying to sell this as a commercial product because while you don't need an IMBE decoder for a repeater you will still be using all sorts of IP that belongs to others...
Re: P25 Digital Repeater using Motorola Radios
We are very serious - this is part of Steve Glass's Comp Sci Phd thesis, so we clearly aren't mucking around.
At the moment testing is underway on pure I/Q decoding as opposed to Franks C4FM slicer.
At the moment testing is underway on pure I/Q decoding as opposed to Franks C4FM slicer.
Why? without IMBE I cant see anything in a P25 repeater that's proprietary or IP...Astro Spectra wrote:So the whole "P25 validation circuit" is going to look like a small PC server.
Oh, and here's the thing - you're not going to be trying to sell this as a commercial product because while you don't need an IMBE decoder for a repeater you will still be using all sorts of IP that belongs to others...
Re: P25 ADP AlgoID
Well. I finally found it - I've succesfully captured the data using the OP25 project and GNUradio framework and it all decodes perfectly!
The AlgID is 0xAA.
Its sad that 90% of the people that look at this post won't understand the significance of what has been achieved with this project, but here it is anyway
The AlgID is 0xAA.
Its sad that 90% of the people that look at this post won't understand the significance of what has been achieved with this project, but here it is anyway
Re: P25 Digital Repeater using Motorola Radios
Thanks to Max, KA1RBI, some more progress has been made on OP25.
I used a Ubuntu running inside VMware, and a disc tapped uniden scanner to create the following screenshots:-
The first one shows a grab of an ADP transmission, the second shows the output of the C4FM slicer (work continues on a I/Q decoder that handles both CQPSK and C4FM)
Cheers,
Matt
I used a Ubuntu running inside VMware, and a disc tapped uniden scanner to create the following screenshots:-
The first one shows a grab of an ADP transmission, the second shows the output of the C4FM slicer (work continues on a I/Q decoder that handles both CQPSK and C4FM)
Cheers,
Matt
Iiiinnnntersssting!
Very interesting. Thanks for posting this.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
Re: P25 ADP AlgoID
No worries - All that was used is Ubuntu running in VMware, and a discriminator tapped Uniden scanner..
There are other things coming too
There are other things coming too
Re: P25 ADP AlgoID
Cool
- The Pager Geek
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Re: P25 Digital Repeater using Motorola Radios
Lookin Sweet
Experienced Provider of Useless Information
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Re: P25 ADP AlgoID
Hi Matt, mabie you could post up a step by step on how to get it working through vmware. I think what you guys are doing is fantastic, keep up the good work.
Cheers
Cheers
Re: P25 ADP AlgoID
No worries, I need to update the wiki with some doco on how to do it.
I used VMware Fusion on a Mac, though it shouldn't be too hard to get it running on other platforms.
I used VMware Fusion on a Mac, though it shouldn't be too hard to get it running on other platforms.
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Re: P25 Digital Repeater using Motorola Radios
Thanks mate highly appreciate it, would love to get it going and having abit of a play.
Re: P25 Digital Repeater using Motorola Radios
Back on the topic, transmit code has been added to OP25. One step closer to a software defined repeater.
Re: P25 Digital Repeater using Motorola Radios
Has anyone been able to do a cross band with gm300's succesfully? I can pass VHF to UHF Can not pass UHF to VHF any luck.