Signature Wireless Group / Black Mountain

[b52hbuff]

I apologize for meandering in the last thread here:
http://forums.radioreference.com/sa...ussion/234680-crystal-communications-ltr.html

I will dedicate this thread to my observations on this LTR system:
Signature Wireless Group (Black Mountain) Trunking System, Palo Alto, California - Scanner Frequencies

I looked at ths system, because WayneH suggested it would be a good known system to test out the LTR LCN functionalify on the Uniden HP-1. I have made a couple of LCN Finder runs over about a week. Here are a result of the runs

Frequency    LCN Finder   RR.com
461.9000      3                  3
463.5000      4                  4
464.2500      12                12
451.3250      14                14
453.0000      17                17
452.7375      NA                1
464.0250      NA                10
461.2750      5                 20

While I was waiting on the LCN finder to complete, I did some license / frequency research. I put my research in a OneNote notebook, that you can look at here:
https://skydrive.live.com/redir.asp...514E1D28D4CECB58!137&authkey=!ABWtFqDju0RRaD4

From the research, it looks like this system is built from at least three licenses. And there are 'extra' frequencies across those licenses that are not in the RR.com database entry. I haven't tried including these extra frequencies in the LCN Finder until I can confirm that the RR.com information is correct or not.

The other thing I notice is that only one of the three licenses are 'YG'. The other two are 'IG'.

So I would appreciate if folks could take a quick look at the research and let me know what they think. Some things to consider when you look at it.

1. Please look at the 'Santa Clara LTR' tab and the 'Signature Wireless Group LTR' pages. There are other pages in the notebook, but they're not ready for comment just yet.

2. You will see a lot of systems, licenses, and frequencies that look like URLs. They are. As you click on them (in IE, you need to press control when you click), you'll be taken to the appropriate source material in RR.com. I think you need to be logged into your RR.com premium account to get to some of the reports.

My next step is to look at some of the LTR dumps and see what other information can be found.

Some questions for those of you in the know...

If a frequency is listed in multiple sites, is it possible that it would be part of two different LTR systems with two LCN numbers? For example 461.275 is licensed under WPKV537 in Santa Clara and as WIE753 in Marin. Assume that RR.com LCN of 20 is correct. Would 461.275 also have the same LCN in Marin? Are LTR systems simulcast?

Thanks!

 

[WayneH]

Something to keep in mind....this "LCN Finder" is not a sure fire means to identify freqs for a specific system as it appears to ignore (or not provide) the available LCN portion of the transmissions. This is really important as in most cases it will tell you which other LCN's are out there and when the system is busy. Honestly, if you want LTR accuracy you need a true software app or to look at raw data.

A typical LTR data announcement is like this:
A-BB-CC-CCC-DD

A=area bit
B=LCN for monitored freq
C=group ID
D=available LCN (when 0 it's busy, when 31 it signifies EOT)

Simulcast LTR systems don't exist in standard form. There are/were linked LTR systems called LTR-Net. They send a dual LTR announcement. I've never seen a linked or networked standard LTR system by Sig Wireless, Crystal or any other Bay Area usual.

If a freq is licensed for multiple sites it won't be used at both sites; one or the other. It could be in the programming but no doubt the sysop will turn one on or off respectively depending on needs.

 

[b52hbuff]

Something to keep in mind....this "LCN Finder" is not a sure fire means to identify freqs for a specific system as it appears to ignore (or not provide) the available LCN portion of the transmissions. This is really important as in most cases it will tell you which other LCN's are out there and when the system is busy. Honestly, if you want LTR accuracy you need a true software app or to look at raw data.

A typical LTR data announcement is like this:
A-BB-CC-CCC-DD

A=area bit
B=LCN for monitored freq
C=group ID
D=available LCN (when 0 it's busy, when 31 it signifies EOT)

Thanks for playing LTR tutor. Let's start with the easy stuff....

A TRS like Disneyland is 'easy' to figure out because it is a Mot Type II and it also has all of its frequencies listed under a single license. As I'm finding out here, an LTR system appears that it can be constructed out of multiple licenses and not all of them need to be labelled 'YG'.

So with what you just told me, can I assume that there if a frequency is licensed within a very close proximity, then there is a higher probability it could be part of an LTR? I know that it isn't a certainty, because there could be an unlicensed frequency or a mistake. But generally speaking, LTR system frequencies are going to be colocated?

Also, please take a look at my SkyDrive Notebook. It is the same URL as before, but here it is for your convenience:
http://api.viglink.com/api/click?fo...tFqDju0RRaD4&jsonp=vglnk_jsonp_13317464012971

Check out the 'LTR Activity' sub-page. It is under the Santa Clara LTR tab and Signature LTR page. It shows an LTR Activity dump for a couple of days. It is a huge file, which is why I put it on the SkyDrive. But here is a snippet of some entries:

03/09/2012 21:29:47	"0, 4, 4,  7, 3"	Talkgroup Voice Channel Grant Update	Tid:0-04-007	Rpt:4	Goto:4	Free:3
03/10/2012 00:40:49	"0,12,12,253, 4"	Talkgroup Voice Channel Grant Update	Tid:0-12-253	Rpt:12	Goto:12	Free:4

So these follow my basic understanding of the home channel being in the TGID. And we see them in the Goto part of the subaudible message.

And here is a message that is interesting, since it deals with Rptr 20, since the LCN finder wanted to identify LCN20 (from RR.com) as LCN5.

03/10/2012 15:21:59	"0,20,19,241, 9"	Talkgroup Voice Channel Grant Update	Tid:0-19-241	Rpt:10	Goto:20	Free:9
03/09/2012 08:20:52	"0, 5, 2, 47,14"	Talkgroup Voice Channel Grant Update	Tid:0-02-047	Rpt:20	Goto:5	Free:14
03/10/2012 01:08:44	"0, 5, 5,253,15"	Talkgroup Voice Channel Grant Update	Tid:0-05-253	Rpt:20	Goto:5	Free:15

So a couple of questions. If the HP-1 has access to 'Free' and 'Goto' LCNs, I would think that this data would be incorporated into the LCN find algorithm. I'm curious if you'd had specific experience with the HP-1, or just with other radios.

I'm not trying to be a fanboy, and I appreciate your help trying to understand how this decode algorithm might work. Clearly, some information from UPman regarding data used and algorithm implemented would go a long way here...

 

[b52hbuff]

btw, found a great reference on LTR data formats here:
LTR Trunking System technical description

 

[WayneH]

Sorry for the delay...

Based on what I've seen from companies like these is you cannot go off the license data. Count on there being errors once and a while. You cannot always assume what's licensed at a site will be used there, as I've seen the freqs used as other sites they're not licensed for.

Also, and this is the pisser with LTR is when you get an LTR message that has a different "GOTO" channel than the home you cannot know for sure, unless you're listening, whether it's a voice call that's gone to a different repeater or an announcement for current radios to GOTO another channel. You've got to know the context to know for sure. I've done a lot of logging and sometimes there's going to be data that you'll be unsure about. Typically I dump it to Excel and do a lot of filtering. This is for GRE logs though.

FYI, TG253 is for callsign/BSI announcement. There are a few others that are system specific.

The best thing to do is watch a channel in realtime when it's active. This is what I do. As the data messages are announced they'll list all the available GOTO channels. Most of the time they'll announce all the ones in the system. Of course if another is in use it gets dropped from those announcements. I've seen some Crystal Comms T-band systems that wouldn't always show all over the other available channels. I think it's just how their LTR controllers are set up (there is one controller per voice channel; each controller is interconnected with each other and independently programmed).

Looking at your logs, how do you know which frequency is for which set of messages? This is a good reason I don't buy Uniden anymore. Their engineers don't know WTF they're doing when they write these "expert" features. All that data and I can't tell you much of anything.

 

[DSheirer]

@b52 ... were you able to run LTR-Analyzer against this system?

Do you think that your HP-1 may be throwing out any signalling messages it doesn't understand? You should be getting around 7/messages a second when the mobile is active, but your logs on skydrive are only showing around 2-3/messages a second.

The series of group 253 messages you have toward the end of your log are in the same format that an LTR-Net system here uses to notify individual radios when it wants to send them data on a traffic channel.

 

[WayneH]

Group 253 on LTR standard is generally BSI/License broadcast.