Determining LCN

[f494d957]

I am trying to determine the LCN of an LTR system with my BC780XLT using the Wiki "Mapping an LTR System".
http://wiki.radioreference.com/index..._an_LTR_System

I have programmed one known LTR frequency into the first 20 channels of one bank, marked them as trunked, and set the bank for LTR.

I press TRUNK when an ID is active, noting the channel number.

But, I'm noticing that one particular LTR frequency is active on two different channels. Sometimes 489.3875 is active on channel 10, sometimes channel 12.

What does this mean? The frequency is assigned two different LCNs? Is this typical?

Thanks.

[captclint]

Unless there is something about the 780 that make the hold and trunk buttons different than the 796 (my scanner), I don't recall having this problem. I guess I would just keep this up for a while and pick the most frequently used position for that channel. If that position does not receive any traffic when you put it in position 10 and monitor the system, then try 12.

[f494d957]

489.3875 is programmed in 20 times and is assigned LCN 1-20. I'm seeing talkgroups that have HH of 12 appear on two channels.

For example: 0-12-212 is appearing on channel 12 and 10. When I hit trunk, the displayed channel on the 780XLT is 12, sometimes 10.

Does this mean that 489.3875 is used twice in this one system? Once as LCN 12, once as LCN 10?

[captclint]

Originally Posted by f494d957

Does this mean that 489.3875 is used twice in this one system? Once as LCN 12, once as LCN 10?

This is not likely in my experience.

[f494d957]

Then maybe I've discovered a new thing!

I'm hearing the same people with the same LTR talkgroup. But sometimes its on LCN 10, sometimes LCN 12. The same frequency is used.

[n3ncn]

ooopppsss

[f494d957]

Originally Posted by capt_clint

Unless there is something about the 780 that make the hold and trunk buttons different than the 796 (my scanner), I don't recall having this problem. I guess I would just keep this up for a while and pick the most frequently used position for that channel. If that position does not receive any traffic when you put it in position 10 and monitor the system, then try 12.

You changed this post again. I didn't realize you that did.

It receives traffic of the same talkgroup when the frequency is assigned to both LCN 10 and 12, though not simultaneously.

And if this isn't enough -- I just discovered a different frequency that is licensed for the same system that ALSO uses LCN 12 as its HOME.

That's why I'm trying to figure out what's going on. This behavior is not mentioned in the Wiki. I never knew one frequency can be assigned to two different LCNs for the same system, or that two different frequencies of the same system can have the same LCN. This being the case, it all but impossible to map the LCN order of LTR.

[captclint]

Originally Posted by f494d957

And if this isn't enough -- I just discovered a different frequency that is licensed for the same system that ALSO uses LCN 12 as its HOME.

How did you determine this was in fact HOME? Did you put in in all 20 channels, and it always stopped on 12 and no other?

I think you need to stop trying to find more channels and try to monitor the system using what you are pretty sure are correct home positions. You will soon find out whether you have done it correctly, because you will miss entire conversations with the scanner flashing between 2 freq with no sound.

[f494d957]

Originally Posted by capt_clint

How did you determine this was in fact HOME? Did you put in in all 20 channels, and it always stopped on 12 and no other?

Yeah, I programmed it (490.0125) into channels 1-20. Traffic on that frequency spends all of its time on channel 12..

Originally Posted by capt_clint

I think you need to stop trying to find more channels and try to monitor the system using what you are pretty sure are correct home positions. You will soon find out whether you have done it correctly, because you will miss entire conversations with the scanner flashing between 2 freq with no sound.

I have only tried to figure out the one original frequency (489.3875) in addition to the second one (490.0125).

I hear 0-12-212 on 489.3875 (LCN 10 & 12) and 0-12-208 on 490.0125 (LCN 12). Both frequencies are registered to the same owner.

I'm not sure which LCN is HOME for 0-12-212 because traffic spends nearly equal amount of time on both LCNs (which are also the same frequencies, to remind you). And I don't miss any transmissions when I program those two. I always hear sound. So, I don't know which LCN (10 or 12) is HOME for 489.3875. The HH would indicate that the HOME is 12, but this seriously conflicts with the other frequency.

What I'm seeing does not follow what is written in the Wiki.

[n3ncn]

I read the wiki very in-depth. You may want to research more and hit the clickable links to further your knowledge on this. This trunking takes alot of effort to understand. check in the first two paragraphs about "overflow"

[f494d957]

Originally Posted by n3ncn

I read the wiki very in-depth. You may want to research more and hit the clickable links to further your knowledge on this. This trunking takes alot of effort to understand. check in the first two paragraphs about "overflow"

You said something very similar with the first post you made, editing it to "ooopppsss" later.

I have spent a lot of time reading it over and over myself.

Can you be more specific on which part you think I am misunderstanding?

And can you say why am I seeing one particular frequency assigned to two LCNs. And can you say why am I seeing two frequencies assigned to the same LCN, both of which appear to be a HOME channel?? These two questions are the very reason why I started this thread.

[n3ncn]

I'm not big on LTR systems but it's not at all hard if you read. When I got into trunking years back I would read on it and as soon as I saw something I stopped reading and did what they said. Found myself reading again to get the whole picture. Go to the wiki page you have linked and read the section titiled "How Do I find the correct Home frequencies in a known LTR System?" And read it carefully. it will answer your questions. maybe not in-depth but should answer them. Mark

[n3ncn]

I found alot of other parts that explain it. You may really have to concentrate on reading this. It's all there. Just go slow and concentrate.

[f494d957]

Originally Posted by n3ncn

I'm not big on LTR systems but it's not at all hard if you read.

Yet, earlier you said, "This trunking takes alot of effort to understand." So which is it?

Originally Posted by n3ncn

When I got into trunking years back I would read on it and as soon as I saw something I stopped reading and did what they said. Found myself reading again to get the whole picture. Go to the wiki page you have linked and read the section titiled "How Do I find the correct Home frequencies in a known LTR System?" And read it carefully. it will answer your questions. maybe not in-depth but should answer them.

I found alot of other parts that explain it. You may really have to concentrate on reading this. It's all there. Just go slow and concentrate.

"Should" answer them? No, if you want to claim that the answer is there, it will and must answer them.

If there is a section that describes one frequency that is assigned two different LCNs or one that describes two frequencies that are assinged the same LCN, I do not see it.

So, if you have information that can help, please share it. Pinpoint the section. Quote a phrase that I can search for. Otherwise, you're not helping at all. In fact, it looks like you've joined my thread only to cause trouble, and you are discrediting yourself by doing it and by giving your contradictory statements. (I can see that causing trouble is a very popular passtime in this place. I have never seen such active moderators.)

So please...support your claim or move on.

[n3ncn]

Trunking is easy After you get the hang of it. My systems work great. I Don't try to cause trouble here. I've been here since 2002 and dealing with radio's since 1977.
Sorry you can't figure it out. I now close my comments to your thread.
Good luck

[cg]

I have never seen that activity on any of the systems near me however, it seems possible it is LTRs form of networking.
I may be way off with this as I cannot find the article but here it goes.
I recall reading that the reason for separating the LCN (1, 7, 14, 20 rather than 1, 2, 3, 4) is to allow other users in a wide area network to use the system. A user may have a talkgroup of 12-123. When they leave the area and go into a second system's coverage area, the radio will try to contact, the HOME channel will change and go up in sequence trying each (13-123, 14-123) until the system responds.
In your case, perhaps the first freq that has both HOME channels IDed, is the one that the radio is roaming to and the other HOME LCN 12 frequency is where it's regular HOME channel is.
If this is the case, then 10 is likely correct and there are perhaps 2 separate systems used by that company.

chris

Patents are tough to read but try one for LTR:
http://patft.uspto.gov/netacgi/nph-P...y=PN%2F5159701

The home channel backup feature of the present invention assigns a backup channel for each transceiver on the trunked system. Generally, for each trunked system, one non-home channel will be assigned as the backup channel for all of the home channels on the trunked system. In the event that a transceiver does not detect any communication on its home channel for a predefined period of time (in the preferred embodiment, approximately 1 minute), the mobile switches to the preassignee backup channel. As the home channel repeater means normally is broadcasting an update control message at least every 10 seconds, if the mobile has not received any communications for the last six update periods it will assume that its home channel has gone off the air and will switch to the backup channel. After switching to the backup channel, if the mobile transceiver does not detect any communication on the backup channel for a predefined time period, the mobile will presume that it has gone out of the coverage zone of the trunked system and, if it has been programmed to do so, will attempt to automatically register on any of the other available trunked systems in the wide area network that the mobile is a user on. ........ It will be understood that the operation of dynamic reconfiguration on the trunked system requires compatible software programming in both the RNT switch and the mobile, along with reprogrammable memory in the mobile for those functions that will change or reprogram initial or default values that have been stored in the mobile. For example, a given transceiver is originally programmed with a specific set of authorized groups for the trunked system it will be operating in. These groups a may be stored in a table in memory (i.e., an EEPROM) in the mobile logic unit. If the mobile were to travel out of the coverage zone associated with the trunked system it is assigned to and into another coverage zone, the mobile could also have stored in its memory registration channels associated with adjacent coverage zones that it would allow the mobile to contact those trunked systems. When it is determined that the mobile has left the original zone and entered a new coverage zone, the mobile would contact the trunked system in the new coverage zone and request automatic registration in that zone. The new RNT switch for that zone would contact the home RNT switch through the registration to verify that the mobile was allowed to register in the new coverage zone and inform the home RNT switch that the mobile had left its coverage zone. Once the mobile is registered in the new coverage zone, the new RNT switch might reprogram the group that the mobile was associated with might reprogram.

[captclint]

Chris..good point. Could also be units from another system nearby. I have that problem. The way you will know is when you put in LCN 10, and there is no traffic. While the same freq may be used by the same FRN in another system, it will be assigned a different LCN so there is no "conflict". Since you are pretty sure of the new freq being LCN 12, I would go with that for now.
OK, down to basics:
1. How many frequencies are registered to this system?
2. Are there other systems in the area registered to the same FRN, and are they within listening range of your location(15-25 miles)?
3. Are there any other LTR systems registered in your area? While it is not likely a different FRN would be licensed for the same freq in the area, it might be a "cooperating" radio service with your main FRN.

Suggest you concentrate on getting LCN's for the other freq's. Once you get familiar with the users and their conversations by monitoring the system of known good LCN's, you may be in a better position to recognize "foreign" conversations.

One possible confusing point in the Wiki is here:
"On the BC796D, hit the Trunk Button, and it will tell you which of the 20 positions received the transmission.... If the audio is on talk groups A-05-GGG then that frequency is likely to be channel 05."
The actual position is what's important, not the TGID. That is only there for those cases where the position found IS actually a home channel for one or more of the users. From what you have said, you are actually seeing different positions in the scanner for one freq, so I don't think that is your problem. Likely it is another system.

[cg]

Where are you? Unless it is a new system, maybe someone already did all the work.

chris

If by chance you are in or near Houston TX, you should look at FleetTalks system on this site.
http://www.radioreference.com/module...me=RR&sid=2558

[wayne_h]

Originally Posted by f494d957

And can you say why am I seeing one particular frequency assigned to two LCNs. And can you say why am I seeing two frequencies assigned to the same LCN, both of which appear to be a HOME channel?? These two questions are the very reason why I started this thread.

With the method you're using and what you've described you aren't going to figure out the home channel. When a TG trunks out because its home channel is in use you will not see a change in what considered the "talkgroup" ID. There is more data the scanner isn't showing you, like the actual channel number for the frequency. The easiest way to see this data is with a PRO-97 or its mobile equivalent.

[f494d957]

Originally Posted by capt_clint

OK, down to basics:
1. How many frequencies are registered to this system?

I'm not exactly sure.

These frequencies originally started out as industrial/business pool conventional (IG) and switched over to LTR (I'm seeing talkgroups with each

Yet they were never updated in the FCC database. They are still listed as IG. They are all registered to the same business with transmitters in the same location. The Wiki mentions this same phenomenon.

Originally Posted by capt_clint

2. Are there other systems in the area registered to the same FRN, and are they within listening range of your location(15-25 miles)?

Yes.

Originally Posted by capt_clint

3. Are there any other LTR systems registered in your area? While it is not likely a different FRN would be licensed for the same freq in the area, it might be a "cooperating" radio service with your main FRN.

There are several LTR systems that are registered in my area, and many more that are LTR but whose registration has not been updated.

Originally Posted by capt_clint

Suggest you concentrate on getting LCN's for the other freq's. Once you get familiar with the users and their conversations by monitoring the system of known good LCN's, you may be in a better position to recognize "foreign" conversations.

Which I have done. I'm still confused why I'm seeing one frequency that is assigned to two different LCNs. I hear the same people talking on both.

Originally Posted by capt_clint

One possible confusing point in the Wiki is here:
"On the BC796D, hit the Trunk Button, and it will tell you which of the 20 positions received the transmission.... If the audio is on talk groups A-05-GGG then that frequency is likely to be channel 05."
The actual position is what's important, not the TGID. That is only there for those cases where the position found IS actually a home channel for one or more of the users. From what you have said, you are actually seeing different positions in the scanner for one freq, so I don't think that is your problem. Likely it is another system.

But how would anyone know? These frequencies are registered to the same company, they have the same FRN, their transmitters are in the same location.