How can you determine a system is LTR-Net?

[jje64]

I have a VHF High Band system in my are of PA. It appears to be an LTR system, but I cannot track it with a BC785D. I have not been able to run ltrdump or ltrtrunk (yet). Is there a way to tell if the system is an LTR-Net system with just the radio?

The data bursts appear to be once per minute during system quite times.

Thanks
John

 

[DaveH]

What you're hearing is not LTR, LTR-Net or related. It's
the keyup heard on Motorola Smartnet/SmartZone voice
channels. LTR-Net channels that I hear key up every
1.25 seconds i.e. 8 times faster than LTR, plus one
extra "beat" every 10s for LTR compatibility.

Dave

 

[INDY72]

LTR Standard data bursts every 10 or so seconds,... LTR Passport data bursts every 2 or so seconds.

So what your describing sounds like a VHF Motorola Type II system. Try it as such and see what you come up with. Also what is the system licsensed to? If its a government entity, it could very well be a ASTRO system, and thus have digital TG's on it.

 

[jje64]

I don't believe it is a SmartNet/Zone system as there is no control channel in use, and the radios in use on the system are Radiu M1225-LS radios. I am fairly sure those radios did not do Smartnet.

One user, for example, appears to stay on the same freq all day with fairly high usage. However, using two radios I was able to see they do get trunked off to another freq when their typical freq is busy with another user. I can also hear digital subaudible data leaking through the radio when the user is talking. I have done a tone search and found them not to be using DPL.

I suppose it could be a SmarTrunk system. When I get some time I will have to put a service monitor on the channel to look at the subaudible info.

 

[DaveH]

10s is typical for LTR on 800MHz, but for whatever reason here I find UHF is usually 11s, and VHF 5 or 6 seconds. It may vary by
location. There is now a ton of VHF LTR in N. NYS in the 150-154MHz range.

Dave

 

[INDY72]

I have not heard of Standard or Passport LTR's that burst only once a minute........ Though the timing seems to be up to individual system management. Data Bursts can set on a per system basis, even disabled....

I don't have experience with a Multinet LTR, so not sure what they sound like....

Also note- Older Motorola VHF TRS used Subaudible Digital Data, not a CC per say..... After all this was initially how scanners were set up to trunk track VHF/UHF Motorola.. subaudible data.

Anyone know how MPT's operate?

 

[WayneH]

Also note- Older Motorola VHF TRS used Subaudible Digital Data, not a CC per say..... After all this was initially how scanners were set up to trunk track VHF/UHF Motorola.. subaudible data.

Negative. Motorola has always used a 3600 control channel for OBT systems.

Anyone know how MPT's operate?

Dedicated control channel. No sub-aud.

-Wayne

 

[DaveH]

Also note- Older Motorola VHF TRS used Subaudible Digital Data, not a CC per say..... After all this was initially how scanners were set up to trunk track VHF/UHF Motorola.. subaudible data.

Milf, I think what you're thinking of was, the original PRO-92 used sub-audible data to trunk Moto systems on all bands including 800MHz (and 900MHz?). Priority Scan feature of the system confused it (an oversight...) which caused 92 users a load of grief. They went to CC trunking for the A and B versions on 800 (900?).

Back to the original question, if it's a Moto voice channel you would hear a short burst of disconnect tone at the end; easier to heard with headphones. I forget the frequency (176Hz?).

Dave

 

[INDY72]

The Moto disconnect tone to the naked ear would sound like iether a short series of beeps.. or a MMMM type of sound...

Example:

Unit 23, 10-07. *click* MMMM

Or-
Unit 23, 10-07. *click* rapid beeps

But I have heard a couple that are like a combination rapid beeps and the hum. I think it depends on the exact setup of the system....

VHF EDACS has a truly irritating disconnect in my opinion anyway...
Rapid beeps, low buzz,.. then the EDACS tones.

On most VHF LTR Standard, the disconnects can sound just like conventional radio discon toning.... except the next part of the convo might be on another repeater hehehe.. Or you might hear another agency key up "in the background" sorta like in the old "Walked on ya" days....

 

[loumaag]

John, I have to agree that this is probably not a LTR system; however, you can determine it pretty easy. Take whatever is the most active freqency and place your scanner in LTR mode, then program that same frequency into slots 1-20 of the bank. Tell your scanner to scan (in trunk mode of course) and see what happens. If you are listening to a LTR system, you will come up with something on one of those slots and if it consistantly reads the same "repeater home" channel of the LTR TG info, you have started to solve the puzzle.

On the other had, I tend to agree with DaveH, I think you have stumbled on a Motorola system. The fact that you haven't found the CC is no surprise. (You should be here in SD!) I am not sure about this for Uniden radios, but RS (the GRE ones at least) still will decode the sub-audible TG info carried on Motorola analog systems. What I mean is if you program the frequency in MO mode, then place it in MANual mode on the frequency; when they talk, if it is a Moto analog signal, it will give you the TG number.

Hope you get if figured out.

 

[jje64]

Lou,

The process you describe is exactly what I have been doing to map our the LCN's. What I did not mention in my original post was one channel in the license did come up as LCN 4. It was the least busy channel. The most busy channel never shows up via this method. This is why I am stumped. LAte at night when the company who uses the channel is closed I continue to hear the once per min. burst.

The system repeaters are only a few miles from my house on a ridge so if there was a Mot CC I know I would hear it. Additionally, I have a good handle on the VHF HB usage in the area, and there are no CC's anywhere between 150 and 160.215 MHz.

Thanks for the comments, though. I will continue my quest and update as I find more info. I need to get ltrdump and ltrtrunk running. They may shed some light on the topic.

Regards
John

 

[INDY72]

Hmm could also be a "Hybrid" LTR combining LTR Passport and LTR Standard.. if you ever get a chance to just monitor this one system exclusively for a long period of time,.. listen to the data bursts on ALL the freqs..... see if you get a "blend of regular DB's(every 8 to 12 seconds), and PP-DB's(every 2 or so seconds)..... when trunk tracking,.. the PP TG's will not show up.. while the standard TG's will. And running LTRTrunk/LTRDump will definitely help you out.. good call on that.

 

[EricCottrell]

Hello,

The LTR-Net systems around here have one channel that is on continously, usually Repeater number 20. This is the backup home channel and has the activity of the whole system.

Passport can handle Regular LTR and Conventional channels. If this is a Passport system then LTRDump should decode it.

73 Eric