Batboard

Hi
We have a Motorola trunking system installed with HT1250LS portables and CDM1550LS base stations. Our trunking system has 5 channels that we should be able to access. However, in the past couple of weeks we have had problems getting an open channel when we key the mic. We either get a lower tone beep (busy channels) after a couple of seconds or no beep at all of any type. You can usually get an open channel after keying the mic four or five times. I don't believe the problem is related to traffic volume as this is also happening late at night when very few people are using the system.
Anyone out there ever have this problem??? or any thoughts on this?????? Thanks in advance.

Presuming nothing has changed with the portables and mobiles, check with the people who maintain the system to see if any changes have happened recently that might account for this.

It could be a several things.

First thing I'd check would be the infrastructure...repeaters & controllers. If a couple of them are down, it'll really impact the system performance. Even if they are "up", they could require alignment...things have to be pretty close to spot-on for the LTR data to work properly.

Also, maybe it's a coverage issue? If the system runs everything through RF filtering equipment to a common antenna, perhaps it or the cable run to it has degraded.

Lastly, what are the firmware versions of your mobiles & portables? There have been several LTR bugs fixed over the years through firmware updates. As well, I've read some posts which indicated the CDM1550ls control heads (where the LTR smarts reside) had issues over time in some systems.

Bottom line, you need someone with experience troubleshooting these systems to get to the source of the issues.

Todd

how many sites are there and how far away from them are you when this happens? and what kind of system is this, is it yours or your departments or are you renting it?

Yes, lots of unanswered questions. We're going to need a bit more info. in order to properly attempt to diagnose the problem.

Thanks for the responses. I will try to give you more info but unfortunately our distributor hasn't been overly helpful and has filed for bankruptcy!
Some "experts" have said this may be a power issue. Our system does not have any repeaters for a plant that is about 0.5 miles by 1 mile in size. The buildings are all made of steel walls. We have tried changing the power levels on the CDM1550LS base stations. When the base station power was lowered from 25 W we could not even get a channel (frequency) with them. So, they have been increased in power back up to 25 W. I believe the HT1250LS portables are set for 5 W ( and I don't believe they have an analog setting for power).
If helpful, I could obtain the models for the trunking system. We have thought about trying to shut down one channel at a time (if possible) to see if we do have a problem with one channel. Currently over the five channels (frequencies), they are subdivided into approx 40 sub-channels. I don't know how these are multiplexed. At this point it is hard to know if this is an analog or digital problem.
If I am missing critical information, please let me know and I will try to obtain some more details.
Thx in advance

You can't have LTR without repeaters.

Increasing power from 20W to 25W is negligible, less than 1dB of signal increase there (you only get 3dB when you double the power...)

The system is definitely not digital, the CDM series is not capable of this modulation.

Now the question is-- where is the LTR site actually located?

I think by "repeaters" he means something to give more coverage throughout his building. The 5 "channels" referred to are his repeaters.

mrsask1, since you indicate the system worked up until a few weeks ago, and judging by the size of your building, it leads me to believe you likely have some sort of "distributed antenna" system, or a "leaky feed" system to give you proper coverage. All it may be is a bad connector or cut cable somewhere...but, it's all supposition and you really do need someone with some experience to have a look at things.

Todd

Something else that may be helpful, is where you're located and whether or not your system is in the database of www.radioreference.com

If your vendor isn't being supportive or helpful, a wealth of information can be gathered by searching through their database, licenses, locations, etc.

-Josh

To clarify, yes we do have LTR with repeaters in one central location but no other repeaters in the plant.
We have five carrier Tx frequencies and five Rx frequencies with approx 40 subchannels. Although we cannot get an open channel on many occasions it seems as though we rarely use all five channels at once (at least that what the trunking usage time is indicating)
Could this be a grounding issue? If so, what is the best way to ground the trunking system?? I am told that with RF certain ground points are critical.
To try and add some helpful information, we are also occasionally having one other problem. I don't know if this issue is related OR if it is a separate issue (so I hope not to lead you astray). We were told that this system should NEVER have "talk over" but it is happening. This is when you press the mic and get an open channel but someone else is talking at the same time (although the voice quality of his call is degraded or "crackly")
Thanks again for any feedback. It is greatly appreciated.

One other question. Todd mentioned it could be an alignment issue for the LTR to work properly. Are you talking about checking the carrier frequencies with a spectrum analyzer or what do you suggest??

mrsask1 wrote:One other question. Todd mentioned it could be an alignment issue for the LTR to work properly. Are you talking about checking the carrier frequencies with a spectrum analyzer or what do you suggest??

Well, as a start. Whatever controllers you're using would've had a detailed alignment procedure outlined in it's corresponding installation manual in order for the technician to be able to interface it to whatever repeaters you're using. In particular, the LTR sub-audible data must be within certain deviation parameters for the radios to work properly.

An easy thing to do is take a group of people with radios & go to where the repeaters are. Key up the radios on different talkgroups in sequence & see if all 5 repeaters go into use, or if you get busies before that. Assuming your radios are properly programmed, you shouldn't get busies until all repeaters are in use. If everything appears ok while viewing the repeaters, then you can start thinking that it's a likely coverage issue, and since it used to work, something in your antenna system has changed. It doesn't rule out that there are other issues, but it's a start.

I did exactly this yesterday. With the help of someone I keyed up each radio one at a time up to a maximum of 5 radios and all repeaters picked up as expected. There were NO busy signals. I could also try this experiment in other areas of the plant (although obviously I would have to have someone watching the repeaters)
As I mentioned before, our plant is only 0.5 miles by 1 mile which has a number of steel buildings. It could definitely be a coverage issue as we have ALWAYS had this problem....it just has become worse in the last couple of weeks (as someone has tried changing the power output of base stations...and strangely enough, at the same time the performance of the portables has degraded....a coincidence?)

mrsask1 wrote:Thanks for the responses. I will try to give you more info but unfortunately our distributor hasn't been overly helpful and has filed for bankruptcy!

Do these same people maintain the radio system in any way? if so, that may be your issue

So far, it is the same people.

where is the country are you? you need a competant tech to take a look at your system. Doing this over the net is like asking us to diagnose some issue with your car, and all the info you can give is "it is red with 4 doors".............FatBoy

FatBoy wrote:where is the country are you? you need a competant tech to take a look at your system. Doing this over the net is like asking us to diagnose some issue with your car, and all the info you can give is "it is red with 4 doors".............FatBoy

Hence why I brought up "find it on radioreference.com "... Finding the name of their company in the state/county/country/wherever they are located at will bring up the license, frequencies, location of towers etc etc etc all in one shot.

-Josh

Here's a couple more Q's..

1 Did the system EVER work properly?
2 Is the repeater infrastructure located on your property and owned by you or is it owned/maintained by the bankrupt dealer and located on their tower or off of your property?

LTR trunking can be tempremental at times. We still don't know whether this is VHF or UHF although most are UHF. If it worked and now it doesn't, chances are that there is a problem in the infrastructure or you have excessive interference on your home channel receive frequency. Multichannel systems should use transmit frequency combiners and receiver multicouplers to interface everything to the antenna system. The comment of the "talkover" issue could be some sort of intermod problem on the RF side or could be a programming issue in the controllers.

Judging by your posts, you are the end user left hanging by your service provider and not in the radio business. My humble opinion here is to find another service shop with experience with LTR trunking systems. There are SO many variables that can be happening that you need a experienced tech looking at things. If you own the system, you have a sizable investment in your equipment and you need it to work right AND need it to work within the FCC rules on your correct coordinated frequencies and power levels.

We can help you find a shop with a little more info. I know you have Motorola mobiles and portables. Are the repeaters Motorola too? There should be 5 controllers in there too, most are 1 rack unit high. Look for a name like Trident or TNT or Zetron, maybe even CSI. With this info plus a general idea of where you are at, some of "in the biz" could point you in a positive direction.

Dave

Thanks for the info Dave and to those others that have posted. I thank you for the understanding as I was asked to take this on and really don't know much of the details. As far as getting extra help on this, I believe we only have the one provider in the city (ours). We are located in cental Canada and we would have to bring someone in to troubleshoot this.
As for your questions Dave, here is what I found out.
1) This is a UHF system with five Trident trunking logic controllers along with five Motorola RKR1225 repeaters.
2) This system has ALWAYS given us problems in regards to trying to always successfully get an open channel. However, since there was some experimenting in power levels with the base stations, the problem has become worse.
3) This system is owned by us and all the equipment is on our property.
Some further info. This plant has a large number of mechanical and electrical devices onsite which may lead to excessive interference. As well, there was some testing done and it seems there are some "dead spots" in the plant (although most of our problems exist outside these "dead spots"). As mentioned previously, our plant is only 0.5 miles by 1.0 miles in area. Dave, you did mention possible excessive interference on the home channel receive frequency. I would assume this was something that was checked previously but I am not sure (is that easily changed to one of our other four Rx frequencies??)
I just looked at the usage for the last 11 hours and we have NOT used all five channels AT ONCE during this period of time. Therefore, I would assume this is not a traffic volume issue.

Glad that you're learning about your system, but in reality you're gonna be spinning your wheels unless you can confirm first & foremost that the infrastructure (ie: repeaters & controllers) is properly aligned. It may have drifted, or the company that installed it may not have done it properly (they did go under, after all, right?). At a minimum you'll need a decent radio service analyzer, and the Trident installation manual. You can probably download it from their site, but I'm not sure about that. Secondly, you haven't given your radio's firmware version, which I mentioned in my first post. Early firmware versions had plenty of LTR bugs, and upgrading might solve much of your issue. The firmware version can be found under the 'radio information' tab in the CPS. Lastly, the GR1225 have known issues with the RF power amplifiers going bad. You may just hve a couple of repeaters with bad PA's. That at least can be easily confirmed with a wattmeter, if you have one or can get one.

I'll agree with Wavetar on this also. I beat my head for more than several hours on LTR issues only to find out the radios were "stupid" inside (Read early GTX radios for the /\/\ techs...). PA failures are a reality on the R1225 radios if not set right also. If the home channel has any kind of problem, it can render those radios using that channel as home useless.

If you have the radio programming CPS, read one and post the firmware version as Wavetar suggests. There are definitely issues with earlier versions especially if you have a narrowband system. Checking basics like the output power on each channel is a necessity also. Just make sure you get a wattmeter that will work at UHF frequencies, a "CB" type meter just won't cut it.

As far as changing RX frequencies to one of the other channels.... can't happen unless the entire fleet is reprogrammed. If the radio itself is bad, it can be swapped BUT it has to be realigned to that controller.

Dave

Sorry, I did forget that firmware info. Here it is:

CDM1550LS - ver. R05.05.17

HT1250LS - ver. R05.10.05 (Can I assume this is a date YY/MM/DD?)

I will go to Motorola's website to see what the latest versions are.

Todd

no those numbers are definately not a date code but they are newer firmware numbers within the last year and should be fine

I worked at a Casino Where we initially had RKR-1225s for the base repeaters. The problem? Well, after some heavy use, The RX would start to get real scratchy and stay that way. Come to find out the the RKR-1225 PAs (Transmitter modules) would "Melt Down". Seems that there was a heat ventilation/dissipation problem with those. This may or may not have been corrected by now. This happened a few times until they had enough and went to MTR-2000s and had no further issues. Bottom Line, Have your Watts Out checked on the Service Monitor and the Amp Draw. And yes, also have the alignments on the base stations, TX Combiner Etc. checked. Plus have the antenna connections checked. If you have 2 antennas Tx and RX they need to be properly separated (20 feet) from each other as well.

Thanks 2wayfreq. That is some good info. Our distributor is coming out to do some checks next week. They did look at the logic controllers and found that the sensitivity settings were not consistent. Some were high and some were low (I don't know what the acceptable parameters are for this).
You did mention checking AMP DRAW - is there something internal to check this or do they need an external meter to check the current??
Also, I assume the alignment and power output is checked out the 1225s ??

FYI, we traced this problem to lower power output of channel 1 power amp. We still have some quality issues but we have significantly decreased the number of times we cannot get an open channel. Thanks to all.

You had a PA fail on channel 1, mark this down as it is the home channel for all of your radios.

Bad Idea, not the norm to leave all of the radios on 1 home channel.

Break up home channels into separate channels in your programming so your system does not leave you down as another channels PA could have been in good shape and you would then had coverage back until channel 1 is repaired.

The 1225 repeaters cannot do continuous anything. If you have more than 25 radios on your system that are frequently used, the channels all have to be turned down in RF power to nothing over 25 watts with the cooling fans on constantly.

For the size of your complex you should not need more than 25 watts unless your license says otherwise.

The 25 watts would make up for any line loss and should give you solid coverage.

If you are using a Tx combiner, the frequencies may be so close the insertion loss from the combiner is high and 25 watts in turns into 1 watt out giving your 200 or so foot coverage area.

To overcome this you need amplifiers to increase your output while maintaining good conditions for the 1225.

All of this information is contingent on the setup, we now know about the 1225's, but are lacking information on the antenna type, RF distribution to the antenna system and how you receive the signal from your 1250's.

Your best bet, is still to pay for someone to come in who is familiar with this equipment, analyze and diagnose the ENTIRE system. One service tech, with the proper equipment could invest several hours to one day there and probably solve if not completely diagnose all your coverage problems. Radio maintenance is an art, just like anything else, and should be the realm of someone who does it for a living.

Woudn't be a bad idea to make sure that you are licensed properly at the same time, as well as talk 'Service Contract' with the nearest Motorola vendor.

Thanks for the info CHARTOFMARYLAND. It's interesting that you say that "the 1225s CANNOT do continously anything". I think someone else did mention that after continuous use the quality of the calls was diminished. It does seem that as we have added more radios to the trunking system the quality has been impacted. We probably do have over 100 active radios on a five channel system with ONE home channel. Are you suggesting to break this up into groups with more than one home channel??? Due to coverage issues, we may want to physical separate ONE system into TWO or even THREE. Obviously, this would mean the purchase of more antennas ( I don't know what else would be involved).

mrsask1 wrote:Thanks for the info CHARTOFMARYLAND. It's interesting that you say that "the 1225s CANNOT do continously anything". I think someone else did mention that after continuous use the quality of the calls was diminished. It does seem that as we have added more radios to the trunking system the quality has been impacted. We probably do have over 100 active radios on a five channel system with ONE home channel. Are you suggesting to break this up into groups with more than one home channel??? Due to coverage issues, we may want to physical separate ONE system into TWO or even THREE. Obviously, this would mean the purchase of more antennas ( I don't know what else would be involved).

No addtional anything would be required aside from reprogramming the LTR controllers and the subscriber radios.

Depending on how many work groups you have, you may want to have some of the more active ones broken up on different home channels.

In LTR trunking, and in your case with 5 repeaters. Every radio will try to key up on the home channel, 'Home Channel 1' for access. If it's not in use, then it will be the repeater utilized for the communication. This makes for heavy use of this repeater.

Only if repeater 1 is unavailable, then the radios trying to key up are instructed to use another channel, whether it be 2, 3, 4, or 5. As a result, these other four repeater will see reduced use.

So, why not break the user groups up onto different home channels? Let's say you have five really active talk groups or channels. Move them around to all five repeaters as home channels and break the channel loading up to the other four repeaters.

The trunking will still work, if User group 2 is trying to access the system and it's already busy with a conversation spilled over from home channel 1, it will trunk over to 3, 4, or 5 depending on what the LTR controller tells it to do.

Long story short, only a reprogramming is really required.

-Josh

I do this everyday so no problem,

A note on your comment, when said the users notice a difference in the quality of the system after many users are conversing, you may have problems with your other channels. Just what it sounds like.

If you were to give us a city or town name of your plant we could possibly direct you to a reputable MSS or now PSM to get you straight and keep the system working for more than a year or two.

Also, the maintenance contract mention is a good idea

It could pay for itself depending on the quantity of radios as the parts for the Waris product line, i.e. HT1250,HT750, and CDM1250, are all getting expensive. So a set price for each radio to be repaired is money in the bank if you have alot of radio failures. This does not cover accessories, speaker mics, and batteries unless included in writing.


CoM