Yet another LTR mapping system post

[NW0U]

I'm working on mapping my first LTR system and solving the problems as I come across them but need some ideas for the last problem.

Using a Pro-97. I understand the feature that shows channel number as well as the home channel part of a TGID. Near as I can tell the Pro-97 disconnects the antenna when doing service search or Close Call. It won't stop on the known State DTRS freqs.
However the Funct-Tune works well.

For this system RR database has an incorrect LCN table and the provider company doesn't exist. RR has no TGIDs for this system.

I programmed the channels and some of them were good.
Got some TGIDs going (concrete delivery, a towing outfit and some kind of handicapped bus dispatch).

Then started trying the same channel freqs only 1,2 and 3 Mhz higher/lower. Got a few more channels that way. Got their channel order by watching using LT mode & Manual.

Then started using Funct-Tune to find more. Found quite a few more LTR channels.
Monitoring some of them indicated the correct channel numbers were the same as other frequencies! Must be more than one system in the area! (only 1 listed really close by) Ouch.

So I'm trying to work from the strongest-sounding signals to do the channel map. And that's not too bad but....

Here's the question- are there any other ideas you might have to help me separate the systems from each other?

I consider the channels verified on the same system when I see the same TGID on two different channels at least once (and the voices and signal strength are the same)

Any other tricks I should know about ?

Thanks!

[letarotor]

In my area unfortunately, there are many incorrect listings for LTR systems. Someone went to the FCC database, got a bunch of frequencies and posted them to RR. These listing only provide a starting point for your research efforts. In many cases, people or companies apply for FCC licences but don't always begin using the frequencies right away. And in some cases they may be licenced for a certain frequency at a certain location but use it at another location. I've found frequencies in use and years later still not see an FCC licence pop up. This is rare but keep it in mind. My recommendation is begin my inputting the frequencies you know into the following FCC version 3 database:
http://fjallfoss.fcc.gov/General_Menu_Reports/
Pull up the other frequencies in the same target system, then run the name listed on the system, or contact person's name listed on the system for other systems at the same location. I've found that many times, one LTR system will have multiple FCC licences under different names or DBA's. They do this to throw guys like us off track! Then monitor the new freqs you have found with your PRO-97 and determine which are which. Area codes are a big help in determining what goes where. Don't automatically assume that a certain frequency goes with a certain system. Decoding LTR is like putting pieces into a puzzle. For example, there is one LTR system licenced to a hospital listed on RR that isn't active yet, but has LCNs listed that are actually part of several other systems in the same area. Modify one of your older scanners and try out LTR Analyze. What the program does is tell you how many channels there are in a system and their LCN positions. The PRO-97 will only tell you the group number and actual home channel the group is assigned to. LTR Analyze gives the big picture. Good luck.

Mark

[NW0U]

Originally Posted by letarotor

. Decoding LTR is like putting pieces into a puzzle. Modify one of your older scanners and try out LTR Analyze. What the program does is tell you how many channels there are in a system and their LCN positions. The PRO-97 will only tell you the group number and actual home channel the group is assigned to. LTR Analyze gives the big picture. Good luck.

Mark

Mark, Thanks for the encouragement and experience base.

I'm not so interested as to be willing to modify a scanner but it seems that being organized about tracking frequencies and talkgroups will help to sort things.

It's not just a puzzle about one system but it seems that the box of puzzle pieces has more than one puzzle in it so trying the parts for fit has to be done.

That'll take a spreadsheet of found frequencies vs known and such. Long term project.

I've already posted a new map for one with TGIDs where there were none. Now on to sorting some other signals out.

Thanks!

[letarotor]

NW0U, The scanner mod is really easy to do and I've really enjoyed tinkering with the LTR Analyzer program. Kudos to Eric for developing it. Anyway, all you need is a good soldering iron with a sharp tip, open the scanner and find pin #9 on the dicriminator IC chip, solder a wire to it and add the components as listed in the LTR instructions (all available for about $5.00 total at your local Rat Shack). I use a straight open wire to 1/8" phono plug cord fed through a drilled small hole in the back of the scanner, which runs directly to the audio input of the computer's sound card. Takes less than an hour, and some tinkering with the input sound settings, and you're decoding data.

[NW0U]

Originally Posted by letarotor

NW0U, The scanner mod is really easy to do and I've really enjoyed tinkering with the LTR Analyzer program. Kudos to Eric for developing it. Anyway, all you need is a good soldering iron with a sharp tip, open the scanner and find pin #9 on the dicriminator IC chip, solder a wire to it and add the components as listed in the LTR instructions (all available for about $5.00 total at your local Rat Shack). I use a straight open wire to 1/8" phono plug cord fed through a drilled small hole in the back of the scanner, which runs directly to the audio input of the computer's sound card. Takes less than an hour, and some tinkering with the input sound settings, and you're decoding data.

Thanks for the description. It really doesn't sound very hard. After all the Heathkits I've built I have no doubt I could do the soldering. I just don't have access to a computer to use to crack the systems of interest. My employer won't allow using his computer for that. Cracking LTRs from home isn't high enough on my activity list.
But thanks. I'll keep it in mind if I really get curious here at home.

[NW0U]

I'm going to add to my own q&a here.
I found a system in Boulder, Colorado and started mapping. I looked at the FCC database by frequency and found about 4 of the ones I'd mapped by searching to be assigned to a company. Decided that was the company and submitted it.

A week later I was listening to that same system and heard a CW ID sent. So I decided to wait to copy it. (I'm a Know Code Extra Class ham so this is not difficult).

I copied the callsign then went to the database and found, lo and behold, the company name and the frequencies and the registered address is in California. I'd submitted the wrong company name.This company had more frequencies so I started listening to those freqs. And verified another LCN for that system.

The CW ID is a really important bit of info about the system. Try to use it as much as possible.

[cg]

As was mentioned here or another thread, a company may have several different company names or use initials, etc. One near me is Tower Communications. They also use TCC.

The most efficient way to check for a single licensee that may be using multiple company names is to use the FRN to search. First find one good license for the system you want. Then do a second search using the FRN as the only criteria. I have found that there is usually 1 FRN for multiple names under 1 owner.

Anyway, when using the FCC database, the basic search returns hits for where the company is based. If you want to search based on transmitter locations, use the Geosearch feature (at the bottom of the page).
http://wireless2.fcc.gov/UlsApp/UlsS...chAdvanced.jsp

FYI: There is a bug in the Geosearch feature that I have found that the FCC fixes then breaks again. It will not return results when searching by date - last action date, last week, 100 results; Geosearch - zip code, distance.

chris

[NW0U]

Originally Posted by cg

As was mentioned here or another thread, a company may have several different company names or use initials, etc. One near me is Tower Communications. They also use TCC.

The most efficient way to check for a single licensee that may be using multiple company names is to use the FRN to search. First find one good license for the system you want. Then do a second search using the FRN as the only criteria. I have found that there is usually 1 FRN for multiple names under 1 owner.

Anyway, when using the FCC database, the basic search returns hits for where the company is based. If you want to search based on transmitter locations, use the Geosearch feature (at the bottom of the page).
http://wireless2.fcc.gov/UlsApp/UlsS...chAdvanced.jsp

FYI: There is a bug in the Geosearch feature that I have found that the FCC fixes then breaks again. It will not return results when searching by date - last action date, last week, 100 results; Geosearch - zip code, distance.

chris

I didn't try the geosearch button but I did find that next to each frequency listing is a small hyperlink number that tells the location of that transmitter (or is supposed to anyway).

Good info. Thanks!