New LTR System?

[werinshades]

While on a late night search for Air Tran Airlines at Midway , I was searching in the 450-455 Mhz. area and came across what appeared to be an LTR system . I have programmed a few of these in the past, but my main listening is normally Police and Fire. So I put this out there for you Trumked system gurus to decipher.
What caught my attention was the radio traffic, which I identified as E&R towing. They are privately contracted with Chicago to do non-immediate tows, stolen vehicles, abandoned vehicles..etc. They were sending trucks into various Police Districts and then were told to "check the basket". They were also referring to the S.S. Number, which I know is the Streets and Sanitation number that have to be attached to the Tow Reports that they "put in the basket". They use this term frequently on the Zones when ordering tows.
Ok, so here's what I have: 454.0125, 454.300. These are two frequencies I caught some E&R towing traffic on. I have done a few FCC searches on it without any luck. I do hear frequent "clicking noises" on about 9 frequencies in the 454 Mhz. area, which I believe is a distinctive sound of an LTR system . I am located around Midway Airport, and the signal is strong.
So I leave it to the experts on the Forum who dedicate time to finding new systems. I will give it a whirl as well, but my expertiese on LTR's is limited. So, have a little fun, and let me know what you find.

 

[Chicagostretch02]

I plugged in 454.300 in my Pro 92 original. Programmed it as LTR 20x (channel 1 through 20) and scanned. No LTR number came up despite the clicks. I even held on each channel. No LTR number but the bursts indicate it is LTR. Could it be a single channel use?.......I did not program 454.0125 though.

 

[wirr]

It probably is a Passport trunking system.

 

[chgomonitor]

454.0125 isn't licensed in Chicago. But 454.300 is an "ESP" system, licensed under the paging and radiotelephone service. Looks like a new LTR system, probably Passport (Ugh!) - can't trunk it if it is. Freqs: 454.025, 454.125, 454.250 & 454.300. Nice find Dave, let us know what you hear (if you can stand the key-ups!). Might try monitoring the mobile inputs to the system 5 Mhz higher (459.025, 459.125, 459.250, 459.300).

 

[werinshades]

454.0125 isn't licensed in Chicago. But 454.300 is an "ESP" system, licensed under the paging and radiotelephone service. Looks like a new LTR system, probably Passport (Ugh!) - can't trunk it if it is. Freqs: 454.025, 454.125, 454.250 & 454.300. Nice find Dave, let us know what you hear (if you can stand the key-ups!). Might try monitoring the mobile inputs to the system 5 Mhz higher (459.025, 459.125, 459.250, 459.300).

I'm not familiar with Passport systems, but will do a little research. I know it's not licensed to Chicago, as I didn't expect it to be, but I know E&R does the non-emergent towing for Chicago. Question though, if it's a Passport system, would we still see the LTR Talkgroups popping up even though there not associated with a particular conversation? If I hold on certain channels (I have 20 channels with the same frerquency programmed in as suggested), I see 00-13-142, or 01-08-174 pop up now and then. Could it be an LTR system that I don't have programmed in properly? I admit, I don't dedicate all day to this as this is not my field of expertiese. I did give it brief attention and it was quite busy with LTR Talkgroups popping up. This could be fun to figure out.

 

[EricCottrell]

Hello,

I have run into this problem on the East Coast. The former radio telephone frequencies on VHF and UHF were sold off by Auction and do not easily show up in the ULS. On VHF the channels can be split into two channels by the user so the transmitters are not at the center of the channel. They are at the channel centers on UHF.
http://wireless.fcc.gov/auctions/data/bandplans/pagingLwrband.pdf

There were at least two paging auctions. Auction 40 was the big one.
http://wireless.fcc.gov/auctions/40/charts/40cls3.pdf

The results for the Chicago area show that Victor Communications won most of the channels mentioned.
454.025 GA Victor Communications
454.125 GE Scott MacIntyre also GN
454.250 GJ Victor Communications
454.300 GL Victor Communications

Other channels to check
454.100 GD Victor Communications
454.150 GF Victor Communications
454.225 GI Victor Communications
454.350 GN Scott MacIntyre
454.500 GT Victor Communications
454.600 GX Victor Communications
454.625 GY Victor Communications
454.650 GZ Victor Communications

In general if you hare a keyup every one to four seconds then it is likely a Passport system. Passport uses the same signaling parameters as LTR but has a different data format. I would not be surprised if occasionally a LTR scanner will flash various LTR talkgroups while monitoring the channel.

73 Eric

 

[Chicagostretch02]

Thanks to dave for the discovery and to everyone for the explainations. Great lesson.

 

[werinshades]

Hello,

I have run into this problem on the East Coast. The former radio telephone frequencies on VHF and UHF were sold off by Auction and do not easily show up in the ULS. On VHF the channels can be split into two channels by the user so the transmitters are not at the center of the channel. They are at the channel centers on UHF.
http://wireless.fcc.gov/auctions/data/bandplans/pagingLwrband.pdf

There were at least two paging auctions. Auction 40 was the big one.
http://wireless.fcc.gov/auctions/40/charts/40cls3.pdf

The results for the Chicago area show that Victor Communications won most of the channels mentioned.
454.025 GA Victor Communications
454.125 GE Scott MacIntyre also GN
454.250 GJ Victor Communications
454.300 GL Victor Communications

Other channels to check
454.100 GD Victor Communications
454.150 GF Victor Communications
454.225 GI Victor Communications
454.350 GN Scott MacIntyre
454.500 GT Victor Communications
454.600 GX Victor Communications
454.625 GY Victor Communications
454.650 GZ Victor Communications

In general if you hare a keyup every one to four seconds then it is likely a Passport system. Passport uses the same signaling parameters as LTR but has a different data format. I would not be surprised if occasionally a LTR scanner will flash various LTR talkgroups while monitoring the channel.

73 Eric

Eric, you are right on the money. I can confirm almost all Victor Communications frequencies with brief key-ups as you describe. I can't believe I found this strictly by sure luck. I can confirm to all Chicago area listeners, E&R towing "primary or home" channel appears to be 454.300.They don't jump around much, but i'm sure if it's busy, they will.

 

[chgomonitor]

454.0125

Later that night 454.0125 started popping with "Passport-Like" LTR Key-Ups, so Dave had it right. Even with a good LTR radio like to Pro-97 you aren't going to get much/any data out of these signals and forget trunk tracking it. On-Field the mobile inputs are probably your best bet.

 

[EricCottrell]

Hello,

For Passport you need a low-pass data slicer and a program like LTRDump/LTRTrunk if you want to trunktrack or get talkgroup information. There is likely multiple sites in the system and with the programs you can find out the site frequencies and some information on the neighboring sites.

BTW I read that the Passport data stream from the mobiles is different than what is transmitted by the repeater. LTRDump/LTRTrunk will decode the repeater output but not the mobiles on the repeater input.

73 Eric