Ok, forgive me for this as we are still learning our way through the DMR thing.
We have a large coverage system on the air with over 130 subscriber units, mostly portables. The system was analog for many years and we have a great idea of our coverage. We converted to DMR about 4 years ago and over the last 4 months we have been experiencing serious audio drop out on portable units, to the point were we can not make out the conversation (obviously in digital). It can be compared to picket fencing of an analog system.
We have a mix of TRBO and Hytera radios, and we had orginally installed a XPR repeater and now are using a Hytera repeater. We have a 100 amp installed, three window cans and a angle linear preamp with a 526 duplexer. This has all been in service and nothing has changed, except the repeaters.
We swept the lines, connectors, antennas - all good. All filters, duplexer, and LNA work to spec. All isolation, RX sensitivity, and fidelity of the entire system has been checked, double checked and is all well within spec. We did some prelim looking around with the spec an and didn't notice any major concerns, or nothing that was different than in past. This system operates on a T Band channel.
We can't figure the problem out. It happens across the different subscriber units, even across the different repeaters. Any ideas, as it is becoming a big issue. There is no corrolation between the same radios, or a repeater. It appears to be a system wide issue?
Any ideas to where to start looking, we are out of ideas?
Thanks, Rob
DMR System Picket Fencing Issue?
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Re: DMR System Picket Fencing Issue?
FMROB wrote:Ok, forgive me for this as we are still learning our way through the DMR thing.
We have a large coverage system on the air with over 130 subscriber units, mostly portables. The system was analog for many years and we have a great idea of our coverage. We converted to DMR about 4 years ago and over the last 4 months we have been experiencing serious audio drop out on portable units, to the point were we can not make out the conversation (obviously in digital). It can be compared to picket fencing of an analog system.
We have a mix of TRBO and Hytera radios, and we had orginally installed a XPR repeater and now are using a Hytera repeater. We have a 100 amp installed, three window cans and a angle linear preamp with a 526 duplexer. This has all been in service and nothing has changed, except the repeaters.
We swept the lines, connectors, antennas - all good. All filters, duplexer, and LNA work to spec. All isolation, RX sensitivity, and fidelity of the entire system has been checked, double checked and is all well within spec. We did some prelim looking around with the spec an and didn't notice any major concerns, or nothing that was different than in past. This system operates on a T Band channel.
We can't figure the problem out. It happens across the different subscriber units, even across the different repeaters. Any ideas, as it is becoming a big issue. There is no corrolation between the same radios, or a repeater. It appears to be a system wide issue?
Any ideas to where to start looking, we are out of ideas?
Thanks, Rob
First of all you have neglected to fill in the group on some important facts. Like are you located on a building, tower or out in a field.
What type of antenna are you using? Was it new when you installed it at this location?
How long is the feedline going to the antenna and what type of cable are you using?
Any surge protectors on the feedline?
Why are you using an LNA on the system? Unless you spent some good money and have the needed bandpass filters installed, these units generally cause more problems than they solve.
Have you taken any lightning hits recently at the site?
Are you at a shared site? If so have any new radio transmitters been added about the time you started to have the problem?
Was any work done to any of the other antenna systems at this location?
These questions might seem like we are looking for way too much detail. However, if you have been in the service end of it for as long as many of us on here, these are the items that need to be checked out to find the problem with your radio operations.
Re: DMR System Picket Fencing Issue?
Single site or multiple sites with trunked repeaters?
If multiple sites, can you check link stats for packet errors, framing errors, etc?
Have you checked rcvr desense on all stations at all sites?
Have you earballed it with an analog mobile on the master receive antenna, as well as while driving around? I have heard far away co-channel stations on master antennas that I could not hear on the ground.
Has anyone plotted user reports on a map to see if certain areas stand out? We've had antenna sections fail but still pass return loss tests. The result was loss of gain and a change in the horizon. We've also had other site users install new antennas that changed our pattern.
Could it be the subscriber units are failing? I've had customers swear it was interference causing their woes when in fact it was a lack of maintenance. Batteries going flat, portables with the crunchies, speaker mic cords, dull mic elements, crushed speakers, etc.
Are users trying to talk from inside their cars and trucks with metal vapor tinted windows (aka four wheel Farraday cage)?
If multiple sites, can you check link stats for packet errors, framing errors, etc?
Have you checked rcvr desense on all stations at all sites?
Have you earballed it with an analog mobile on the master receive antenna, as well as while driving around? I have heard far away co-channel stations on master antennas that I could not hear on the ground.
Has anyone plotted user reports on a map to see if certain areas stand out? We've had antenna sections fail but still pass return loss tests. The result was loss of gain and a change in the horizon. We've also had other site users install new antennas that changed our pattern.
Could it be the subscriber units are failing? I've had customers swear it was interference causing their woes when in fact it was a lack of maintenance. Batteries going flat, portables with the crunchies, speaker mic cords, dull mic elements, crushed speakers, etc.
Are users trying to talk from inside their cars and trucks with metal vapor tinted windows (aka four wheel Farraday cage)?
Re: DMR System Picket Fencing Issue?
Here goes,
First of all you have neglected to fill in the group on some important facts. Like are you located on a building, tower or out in a field.
- 190' tower a standard residential and light industrial surrounding
What type of antenna are you using? Was it new when you installed it at this location?
- 10db gain station master, side mounted with a stabilizer arm. Has been installed and operating for about 7 years
How long is the feedline going to the antenna and what type of cable are you using?
- Roughly 195' of 1 5/8 with a LDF jumper top side
Any surge protectors on the feedline?
- Yes, of course. Standard polyphaser lightning arrestor.
Why are you using an LNA on the system? Unless you spent some good money and have the needed bandpass filters installed, these units generally cause more problems than they solve.
-Understood, however your system just doesn't talk until you have some heat on the RX. It is a professional three filter with gasfet assembly. Tuning was checked, and unit is on spec and working. I touched earlier on the fact the RX sensitivity, isolation, filter tuning, and lines have been swept.
Have you taken any lightning hits recently at the site?
- Not that we are aware of?
Are you at a shared site? If so have any new radio transmitters been added about the time you started to have the problem?
Was any work done to any of the other antenna systems at this location?
-Yes, we are. No new transmitters except a 5.8 micro device a bit lower on the tower.
-------------
Single site or multiple sites with trunked repeaters?
- Single site
If multiple sites, can you check link stats for packet errors, framing errors, etc?
N/A
Have you checked rcvr desense on all stations at all sites?
-Yes at the one site, OK
Have you earballed it with an analog mobile on the master receive antenna, as well as while driving around? I have heard far away co-channel stations on master antennas that I could not hear on the ground.
- We have listened thrrough the antenna with the service monitors, etc. We have looked with the spec an - nothing too visible. Noise floor was as it was all along (from what we could see on the spec an)
Has anyone plotted user reports on a map to see if certain areas stand out? We've had antenna sections fail but still pass return loss tests. The result was loss of gain and a change in the horizon. We've also had other site users install new antennas that changed our pattern.
- Bill, it is a fiberglass station master. We have not noticed any other of the tell tale signs of antenna failure or lets say cable/jumper/conector failure. We have put the system on analog and tested for hours with ananlog and no issues noited. Coverage was as it was when the system was strictly analog. Works were it used to, didnt work where it never used to. Even with the digital, when the "picket fencing" or audio drop outs occur the users are generally in known good working spots. However, I do have to say that when the user travels on the fringe of the system, the audio drop outs sound different than what we are experiencing in the known good areas.
Could it be the subscriber units are failing? I've had customers swear it was interference causing their woes when in fact it was a lack of maintenance. Batteries going flat, portables with the crunchies, speaker mic cords, dull mic elements, crushed speakers, etc.
- Don't think so. Some of the hytera units are brnad new. Some of the trbo units are newer, and my portable is a tank that has been around the block. It is happening system wide across different radios, and even a repeater change out.
It almost sounds like the users are stuttering, like the audio is dropping out and coming back in rapid sucession..
Hope this adds some extra light on the situation.
First of all you have neglected to fill in the group on some important facts. Like are you located on a building, tower or out in a field.
- 190' tower a standard residential and light industrial surrounding
What type of antenna are you using? Was it new when you installed it at this location?
- 10db gain station master, side mounted with a stabilizer arm. Has been installed and operating for about 7 years
How long is the feedline going to the antenna and what type of cable are you using?
- Roughly 195' of 1 5/8 with a LDF jumper top side
Any surge protectors on the feedline?
- Yes, of course. Standard polyphaser lightning arrestor.
Why are you using an LNA on the system? Unless you spent some good money and have the needed bandpass filters installed, these units generally cause more problems than they solve.
-Understood, however your system just doesn't talk until you have some heat on the RX. It is a professional three filter with gasfet assembly. Tuning was checked, and unit is on spec and working. I touched earlier on the fact the RX sensitivity, isolation, filter tuning, and lines have been swept.
Have you taken any lightning hits recently at the site?
- Not that we are aware of?
Are you at a shared site? If so have any new radio transmitters been added about the time you started to have the problem?
Was any work done to any of the other antenna systems at this location?
-Yes, we are. No new transmitters except a 5.8 micro device a bit lower on the tower.
-------------
Single site or multiple sites with trunked repeaters?
- Single site
If multiple sites, can you check link stats for packet errors, framing errors, etc?
N/A
Have you checked rcvr desense on all stations at all sites?
-Yes at the one site, OK
Have you earballed it with an analog mobile on the master receive antenna, as well as while driving around? I have heard far away co-channel stations on master antennas that I could not hear on the ground.
- We have listened thrrough the antenna with the service monitors, etc. We have looked with the spec an - nothing too visible. Noise floor was as it was all along (from what we could see on the spec an)
Has anyone plotted user reports on a map to see if certain areas stand out? We've had antenna sections fail but still pass return loss tests. The result was loss of gain and a change in the horizon. We've also had other site users install new antennas that changed our pattern.
- Bill, it is a fiberglass station master. We have not noticed any other of the tell tale signs of antenna failure or lets say cable/jumper/conector failure. We have put the system on analog and tested for hours with ananlog and no issues noited. Coverage was as it was when the system was strictly analog. Works were it used to, didnt work where it never used to. Even with the digital, when the "picket fencing" or audio drop outs occur the users are generally in known good working spots. However, I do have to say that when the user travels on the fringe of the system, the audio drop outs sound different than what we are experiencing in the known good areas.
Could it be the subscriber units are failing? I've had customers swear it was interference causing their woes when in fact it was a lack of maintenance. Batteries going flat, portables with the crunchies, speaker mic cords, dull mic elements, crushed speakers, etc.
- Don't think so. Some of the hytera units are brnad new. Some of the trbo units are newer, and my portable is a tank that has been around the block. It is happening system wide across different radios, and even a repeater change out.
It almost sounds like the users are stuttering, like the audio is dropping out and coming back in rapid sucession..
Hope this adds some extra light on the situation.
Re: DMR System Picket Fencing Issue?
Stuttering, eh? Have you swapped out the router yet? Sounds like framing errors.
Re: DMR System Picket Fencing Issue?
Bill, no router involved. This is simply an out of the box DMR repeater. We originally ran an XPR, now we are using the Hytera version of the unit. Both repeaters have had the same issue present. No IP or site linking involved. We are only running a single, standalone DMR repeater.
I can try to record it and shoot an e-mail to anyone interested.
I can try to record it and shoot an e-mail to anyone interested.
Re: DMR System Picket Fencing Issue?
So, single site, two channels, non-trunking, and both channels are exhibiting similar problems.
Since I have zero experience with Trbo, I'm useless on interpreting any diagnostics built into the product. However, I would be tempted to establish a reproducible baseline of performance from a remote location. ie: your shop. Two mobiles into fixed antennas with good isolation. Mobile 1 at X low xmit power level is received with Y readability in mobile 2 through the repeater.
Since I have zero experience with Trbo, I'm useless on interpreting any diagnostics built into the product. However, I would be tempted to establish a reproducible baseline of performance from a remote location. ie: your shop. Two mobiles into fixed antennas with good isolation. Mobile 1 at X low xmit power level is received with Y readability in mobile 2 through the repeater.
Re: DMR System Picket Fencing Issue?
I did a little searching, and it looks like the Trbo product line is lean on diagnostics.
Re: DMR System Picket Fencing Issue?
Firmware versions in subscribers? Firmware version in repeaters? Do you have units out there with 4 year old firmware???
Re: DMR System Picket Fencing Issue?
Firmware, Yes and yes. I have some original trbo radios that have never been hit with an upgrade, some have, and the hytra radios are brand new. The audio holes have occured with the XPR repeater and now the HYT repeater. Even on the new Hytera portables this occurs.
To me it seems like an RF issue, maybe some inteference on a different order, however we can't seem to see it on the spectrum analyzer or notice anything in the analog mode (switched to analog for temp testing).
- Thanks, Rob
To me it seems like an RF issue, maybe some inteference on a different order, however we can't seem to see it on the spectrum analyzer or notice anything in the analog mode (switched to analog for temp testing).
- Thanks, Rob
Re: DMR System Picket Fencing Issue?
I'll echo escomm's post...firmware versions are important! There have been FSB's released detailing various audio issues between various firmware versions. Even later firmware versions such as 1.08.00 had it's own audio issues, causing 'holes' in received audio, according to some members here. I also recall when 1.07.00 came out, there was an FSB stating earlier firmware revision field units in use with a 1.07.00 repeater caused issues...I'd have to look it up to verify exactly what it said. Motorola won't even talk to you unless everything is lifted to the latest firmware revision...or at the very least, a common firmware version. It's well worth your while to lift everything to the latest, as there have been many audio improvements, both internally in the way it gets processed, to various features such as AGC & noise reduction capability being added.
And that's only within the Motorola world. There's no guarantee that mixing Hytera & Motorola within a system is going to work...other than possibly from Hytera's marketing department...Motorola certainly won't guarantee it.
All the above aside, I had a similar issue with a TRBO system which took me many months to figure out...it didn't help that the customer is several hours away so it was tough to catch the problem while it was happening. In my case, the XPR repeater TX power would drop suddenly, from full power to almost nothing, and sometimes jump up & down during a transmission. Anytime we checked it, everything looked great. I happened to catch it with the spec an one time, saw it varying over 30db while I wasn't moving. It also started throwing off spurs when this happened. Perhaps you have a similar issue?
Just out of curiosity, when were the Hytera field units & repeater introduced into the mix? Why were the XPR's replaced with the Hytera unit?
And that's only within the Motorola world. There's no guarantee that mixing Hytera & Motorola within a system is going to work...other than possibly from Hytera's marketing department...Motorola certainly won't guarantee it.
All the above aside, I had a similar issue with a TRBO system which took me many months to figure out...it didn't help that the customer is several hours away so it was tough to catch the problem while it was happening. In my case, the XPR repeater TX power would drop suddenly, from full power to almost nothing, and sometimes jump up & down during a transmission. Anytime we checked it, everything looked great. I happened to catch it with the spec an one time, saw it varying over 30db while I wasn't moving. It also started throwing off spurs when this happened. Perhaps you have a similar issue?
Just out of curiosity, when were the Hytera field units & repeater introduced into the mix? Why were the XPR's replaced with the Hytera unit?
No trees were harmed in the posting of this message...however an extraordinarily large number of electrons were horribly inconvenienced.
Welcome to the /\/\achine.
Welcome to the /\/\achine.
Re: DMR System Picket Fencing Issue?
Todd and all,
Thanks for the replies. So, the XPR repeater and most of the Trbo portables were replaced within the last two months. I am going to check into the power level dropping out. We may have an issue with the TPL amplifier, that could be interesting??
So, to answer your next question. We plan on going full bore multi site DMR trunked system within this year. So, after many months of research, and lack of other available equipment to market (i.e. tait) we decided to go Hytera. Why, better price, better built, better audio, more features. More features, espically on the infrastructure department. By end of year they will have multi site IP Tier III trunking with no crazy money controllers needed. And, will most likely even have simulcast to boot. We can feasibly build out two three channel sites for what the cost of one moto trident controller for the bulky connect plus system costs.
We opened up the Hytera XPR look alike repeater and it appears well built. RF sections encased in milled aluminum and appeared to me a bit more robust than just two mobile radios shoved in a box. Also, we wanted to support other features such as the Hytera flavor of encryption.
Thanks, Rob
Will look around at our site more on firday and report back
Thanks for the replies. So, the XPR repeater and most of the Trbo portables were replaced within the last two months. I am going to check into the power level dropping out. We may have an issue with the TPL amplifier, that could be interesting??
So, to answer your next question. We plan on going full bore multi site DMR trunked system within this year. So, after many months of research, and lack of other available equipment to market (i.e. tait) we decided to go Hytera. Why, better price, better built, better audio, more features. More features, espically on the infrastructure department. By end of year they will have multi site IP Tier III trunking with no crazy money controllers needed. And, will most likely even have simulcast to boot. We can feasibly build out two three channel sites for what the cost of one moto trident controller for the bulky connect plus system costs.
We opened up the Hytera XPR look alike repeater and it appears well built. RF sections encased in milled aluminum and appeared to me a bit more robust than just two mobile radios shoved in a box. Also, we wanted to support other features such as the Hytera flavor of encryption.
Thanks, Rob
Will look around at our site more on firday and report back
Re: DMR System Picket Fencing Issue?
So, my other portly radio compadre that is part of this system may have stumbled upon what is worng. Way too much audio on the portabe units. It appears that at audio setting "25" and agc on, that there is so much audio that it is causing clipping. So we are now delving into the audio adjustment world... and I will report back.