Crystal Communications LTR

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b52hbuff

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I have a question about the Crystal Communications LTR system in Santa Clara County. Here is the database entry:
Crystal Communications (Loma Prieta) Trunking System, Loma Prieta, California - Scanner Frequencies

I wanted to get some experience with the LTR Finder function on my HP-1. Starting from the pre-programmed configuration for the system above, it looks like there are some serious differences between the Database and what was found. I let the finder function run for about 19 hours from about 3PM yesterday until 10AM today.

So I have a question for those familiar with the HP-1 and the specific system in question. Which do you trust?

Here is what I have found so far:
Frequency LCN Finder / RR.com
490.2375 16 4
483.6625 1 5
484.8875 2 10
484.9625 8 8
490.0625 18 9
484.2375 10 12
483.9125 7 15
483.3125 13 16
489.6625 19 18

Only one of the LCN numbers matches. Note that none of the other frequencies in the RR.com entry besides the ones above were active.

I wanted to get some second opinions before taking a closer look at the licenses..
 

inigo88

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You're definitely onto something. Almost every new LTR system I come across is wrong, simply because the nature of commercial LMR systems is that they are constantly changing, with new customers joining and subscribers getting rid of their radios, changing to another company, the SMR provider going out of business or being bought out by someone else, etc. This system was last modified in 2008, and 4 years is a LONG time for a commercial LTR system.

Definitely check out the FCC ULS licenses, but know that there is a 99.9% chance that they are even more wrong than the database (these companies are notorious for completely disregarding what's in their license and doing whatever with the allotted freqs - sometimes adding unlicensed freqs to their systems, etc., or mixing and matching licenses).

If you'd like your own second opinion, download the program "LTR Analyzer" (details should be in these forums). It's a great program and will list on screen exactly what the LTR subaudible data is saying. After running it for 15 min or so, hit the key to show every LCN it has seen (it will list other LCNs besides the one belonging to the freq you're monitoring when radios are told to go to a Free channel). Do this for each active freq on the system and it will give you a complete idea of what the system is doing.
 

kma371

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You're definitely onto something. Almost every new LTR system I come across is wrong, simply because the nature of commercial LMR systems is that they are constantly changing, with new customers joining and subscribers getting rid of their radios, changing to another company, the SMR provider going out of business or being bought out by someone else, etc. This system was last modified in 2008, and 4 years is a LONG time for a commercial LTR system.

Definitely check out the FCC ULS licenses, but know that there is a 99.9% chance that they are even more wrong than the database (these companies are notorious for completely disregarding what's in their license and doing whatever with the allotted freqs - sometimes adding unlicensed freqs to their systems, etc., or mixing and matching licenses).

If you'd like your own second opinion, download the program "LTR Analyzer" (details should be in these forums). It's a great program and will list on screen exactly what the LTR subaudible data is saying. After running it for 15 min or so, hit the key to show every LCN it has seen (it will list other LCNs besides the one belonging to the freq you're monitoring when radios are told to go to a Free channel). Do this for each active freq on the system and it will give you a complete idea of what the system is doing.
thats a good program, just started using it. i can get the LCN's for each active freq, but how do i find the freqs of the other LCNS on the system?
 

b52hbuff

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Definitely check out the FCC ULS licenses, but know that there is a 99.9% chance that they are even more wrong than the database (these companies are notorious for completely disregarding what's in their license and doing whatever with the allotted freqs - sometimes adding unlicensed freqs to their systems, etc., or mixing and matching licenses).

If you'd like your own second opinion, download the program "LTR Analyzer" (details should be in these forums). It's a great program and will list on screen exactly what the LTR subaudible data is saying. After running it for 15 min or so, hit the key to show every LCN it has seen (it will list other LCNs besides the one belonging to the freq you're monitoring when radios are told to go to a Free channel). Do this for each active freq on the system and it will give you a complete idea of what the system is doing.
I'll try to post a screen shot later, but I'm pretty sure that the LTR Finder uses the subaudible 'GOTO' messages to determine LCN order. There is a dump feature on the HP-1 and it shows you the decoded GOTO's...

The other challenge is that many bay area LTR systems are created under multiple licenses. I got interested in LTR finder because of the system at the Oakland Coliseum. I had active frequencies without PL tones and close call hits. When I started putting the pieces together, the Oakland system is composed from three individual licenses. It was easy to know that all were part of a common system because all of the traffic was related.

In the SMR world, this is going to be harder. The users aren't related, so it'll be harder to know which frequencies match with which systems...
 

kma371

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Isnt it possible that the new LCNs are part of a new system not related to the previous system as assigned in the DB?
 

inigo88

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With LTR standard, there are two types of messages: Goto (the current LCN freq you're monitoring) and Free (the back-up LCN, sometimes several will be announced and alternate). Also an LTR standard system assigns a "Home channel" to each talkgroup, which is simply the default LCN the radio will try and key up on first. The format of each talkgroup looks like A-HH-GGG, where A is the Area Bit (0 or 1), which is the same for every LCN in the system (so if you see a talkgroup starting with 1 on one LCN and 0 on another you are looking at two different systems!). HH is the home channel assigned to that talkgroup, and GGG is the talkgroup number.

Say a user on talkgroup 0-02-001 keys up, their default home channel is LCN 02 from the TG ID. The system sends out a subaudible OSW data message saying "Everyone on 0-02-001 GOTO LCN 02. The free channel is LCN 04." Now a different user on a differed talkgroup 0-02-002 tries to key up, and since they have the same home channel LCN 02 their radio tries to use LCN 02 which is already in use. The system says "No, this is already occupied, you have to go somewhere else. Go to the free channel, LCN 04!" There is a delay while the radios all hop to LCN 04, then the system sends out another subaudible message on the freq for LCN 04 saying "Everyone on 0-02-002 GOTO LCN 04. The free channel is LCN 06."

Obviously this won't last forever since there's a finite amount of LCN frequencies per system (20 or less). If for example LCN 06 is also busy with traffic (0-06-005 is talking) and 0-04-004 wanted to key up on LCN 04 but it was busy and got redirected to LCN 06 as it's free channel, the system will tell 0-04-004 "Oops sorry, all frequencies are in use. All trunks busy." This accounts for the "ATB" message you see in LTR analyzer.

The best way to map out a system is make a list of every frequency you suspect is related to the system. Look at talkgroup IDs from each freq and see if the area bit is 1 or 0, and that will help you begin to narrow them down. Then start looking for home repeater numbers that are different than the LCN you're currently monitoring. If you see 1-05-015 on LCN 19, it's a safe bet that whatever system you're monitoring LCN19 from also has an LCN05. Using LTR Analyzer, make a list of each Free Ch LCN it finds for EACH frequency, and also keep track of the talkgroups you see. If you're monitoring LCN02 and you see it list Free Ch 05 and 09, band scan around until you find freqs that are LCN05 or 09.

What if you find three or four LCN05s? (This has happened to me lol!) That's why you kept track of which talkgroups were seen on each freq LTR Analyzer will keep a log which is very helpful, and again there is a keyboard assignment to display all the current LCNs it has seen on that freq as free Chs, remember to RESET it before changing to a new frequency or you'll get crazy results). The only way to know for sure is to be monitoring one freq on LTR Analyzer, see a 2nd talkgroup get redirected to the new free Ch and then follow it there (preferably with a 2nd scanner) and verify that the same talkgroup you saw redirected is the one you're hearing on that new freq.

I hope that helped! Mapping LTR systems can be a really fun puzzle, especially when the system traffic is low. And the only way to know for sure that you have all the freqs is to park LTR Analyzer on every known LCN and make sure they all announce the same free channels. :)
 

b52hbuff

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Thanks for the ltr lesson. Check out my thread in the uniden forum. I'm hoping the ltr analyzer in the Hp-1 automates much of the rigor you've described.

I'll post lcns for another smr based in palo alto. These lcns appear mostly correct, but there are several missing channels.

And now for the fb admin question, how do we want to move forward? If I can see that lcns are incorrect via the Ltr finder on the hp-1, is that sufficient to make a submission? What is the bar for "good enough"?
 

inigo88

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I would say "good enough" is just telling us it's wrong won't cut it. Spend some time with the system, try and identify some busy talkgroups and then see if you can find them popping up again on other undiscovered frequencies. You have to remember LTR is a "dumb" trunking system, you can't just hook up pro96com and have all the frequencies and neighbors handed to you like you can with P25... It takes work! :)

For your Crystal Communications (Loma) example, first go back through each freq and check whether the area bit of the talkgroups start with 1 or 0 - that will help you narrow down whether you're even looking at freqs from the same system. Then keep an ear out for Freeway Service Patrol (FSP), since they were supposed to be a confirmed user back in 2008. See which of the LCNs you posted you see them pop up on. If your program gives you LCN numbers for unknown freqs, you have to go try and find out what they are.

At minimum, if we're going to go through the trouble of completely remapping a system for you - it has to be something you an say with confidence "I programmed this system into my scanner and it trunktracked flawlessly with the same talkgroups showing up on different LCNs." not "I let my HP-1 sit on it and automatically figure it out, but I didn't want to actually listen because it's boring." The latter does not meet the standard of being confirmed data.
 

kma371

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Interesting read. I'll have to print that out and try some channels this weekend. Thanks
 

b52hbuff

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At minimum, if we're going to go through the trouble of completely remapping a system for you - it has to be something you an say with confidence "I programmed this system into my scanner and it trunktracked flawlessly with the same talkgroups showing up on different LCNs." not "I let my HP-1 sit on it and automatically figure it out, but I didn't want to actually listen because it's boring." The latter does not meet the standard of being confirmed data.
You might not get same talkgroups showing up on different LCNs because the system is never busy enough to shuffle around the grants.

I'll go take a look at some of the data logging inside the HP-1 and see how much of this can be automated. The activity log may in fact show the channel grant on a non-home channel.

What about the negative? How do we prove that a system is totally deprecated? (Like the Disneyland system? ;)). Here is one that I strongly suspect is dead:
Time Slot Trunking, Inc. (Loma) Trunking System, Loma, California - Scanner Frequencies

When I ran LCN Finder, it ran for a while and only got one hit on 464.7.
California Scanner Frequencies and Radio Frequency Reference

None of the santa clara licenses points to Time Slot Trunking or replacement SMR company. Here is a search on another frequency:
California Scanner Frequencies and Radio Frequency Reference

Which maps to a new SMR provider, 'K Comm'. More data on them can be provided here:
WPUC498 (HOWARD M KRAWETZ DBA K COMM) FCC Callsign Details

And here is their site:
K-Comm

So what is the burden of proof that a system should be removed? How long to monitor before it is reasonable to consider the system is dead or deprecated?
 

inigo88

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Yeah I agree I think Timeslot is dead. I last scanned it two years ago and even then there was only an LCN or two left. As long as you spend a couple hours logging each freq and get no hits I'd say you're fine, paying special attention to the home repeater channel identified by the system talkgroups (LCN 03 in Timeslot's case). Maybe check back a second day for good measure. Then if it's still dead I'd say that's more than enough evidence.

I didn't mean to sound harsh before because I think the software is great for verifying whether a system is still active or not. It just won't automatically map a new LTR system for you, and it'll take some manual detective work to figure out which LCNs are part of the same system and which aren't.

And of course, we're thankful that you're trying to make the database more accurate at all. :)
 

b52hbuff

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No worries. I have a thick skin. I appreciate a good give and take. And I appreciate the level of details in your post.

The biggest challenge is when there are misunderstood expectations. Better in my mind to be clear than have someone feel slighted later...
 

jland138

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Didn't Google go mototrbo?

I seem to remember that Google went mototrbo early last fall after the Motorola Mobility deal jelled. I don't think I was "hearing" them on 464.7, but I don't often monitor businesses. I say "hearing" because I think DMRDecode was showing their system using encryption.

Sorry for the weak update. At least for me, it's hard to definitively categorize business systems since there are so many in this area and the players change frequently.
 

WayneH

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Lots of posts so I breezed over a lot...

One of the problems in the Bay Area is frequency reuse. Since LTR lacks so much info to assign it specifically to a licensee there needs to be some sleuthing. Or you read one of the radios live I've done in the past. When you see channels in the database that *you* don't hear anything on that does not necessarily mean they don't exist. LTR systems do not always announce ALL of the other free channels in the LTR system. Some controllers do and some don't. Then there's also the sysop who takes a channel out of service for some reason. I see this a lot. Sometimes the same freq can reappear with a different LCN. It happens and I've seen the programming for it.

Before submitting data to the DB (and I'm pointing my finger at one specific person) make absolutely sure you know it's part of the system, or it's not being used. Sometimes it takes the system to be loaded in a specific way to have channels appear. It's very common for LTR channels to not be home channels and be designated for trunk-out only. I've done a LOT of work with LTR in the Valley and in the Bay Area so I'd prefer to not see anything that's in fact correct get removed.

Regarding Timeslot...much of their channels were being moved to PassPort. It's been a while since I've been to the site where their stuff is but it's possible they no longer have any standard LTR on Monument.
 
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WayneH

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So what is the burden of proof that a system should be removed? How long to monitor before it is reasonable to consider the system is dead or deprecated?
My best advice, get an idea on how LTR works by watching systems in action, not by reading (no engineer perspectives!). The best times to monitor systems are during business hours. Sometimes I sit on info for weeks. My personal database is be frequency, LCN, and then announced TO channels.

Most of the Crystal systems came from me from reading a radio.

I would be very careful with what Uniden radios give you; my 396 sucked at LTR in CC search mode. Unless you're getting raw data, and know how to read it, you might be looking at the real LCN or a TO.
 
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b52hbuff

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Thanks for popping in Wayne. I started finding some anomalies because I wanted to test out the discovery tools on a known system so I could verify it would work. Could you recommend a documented LTR system in Santa Clara that has the properties you discuss? Then we'll know if it works.

One other question is a Trunk Only (TO) the same as a GOTO channel that inigo mentions?

Looks like in this process I've found the new K Comm LTR system. So far it is four channels.
463.400:16
463.500:4
464.275:6
464.650:11

One other question are there private admin notes on LTR systems that show if they were sourced via a radio download or over the air analysis?
 

b52hbuff

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Having more fun with LCN Finder. Latest run is a four day run on this system:
RFC Wireless, Inc. (Mt Presson) Trunking System, Presson, California - Scanner Frequencies

Here is how it aligns with the RR.com database:
Frequency LCN Finder RR.com
484.7625 7 2
451.1625 3 3
484.2625 8 8
490.7125 N/A 10
484.3375 11 11

Still waiting for Wayne to recommend a good reference system to analyze that has an accurate entry. While I'm waiting, I'll take a look at this one:
http://www.radioreference.com/apps/db/?sid=468
 
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