LTR (Logical Trunk Radio) Systems

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LTR or Logic Trunked Radio, is a dinosaur in the trunking world.   In Session 8 of Scanner School, we discuss the multiple forms of LTR Trunking, how they operate, and how the talk group id's are configured

LTR is a different, and almost extinct, form of trunking.

LTR can be thought of as a group of repeaters that are linked together that form a multi-level network.   LTR Standard does not have a typical control channel frequency that is always transmitting.  Instead, you'll find a packet burst every few minutes to notify the users that the trunk system is active.

Each frequency needs to be programmed into your scanner in Logical Channel Number, or LCN.   This means that frequency 1 needs to be in memory location 1 of the bank you are programming.   Likewise, LCN 3 needs to be in the third channel of the bank.

Radios on the system are assigned a Home Channel.   Not every group on the system shares a home channel.   The home channel can be used as a voice channel and will broadcast control information on a sub-audible tone.

Talk Groups are setup in A-HH-GGG fashion.  A = Area Code, either a 0 or 1.   HH = the home repeater.  GGG = the talk group ID.
Ex – A talk group that uses home channel 5 would be written as 0-05-123.

We discuss more about LTR in this week's podcast.

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Show Notes:

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Podcast Transcription:

Welcome to session eight of Scanner School. My name is Phil Lichtenberger. W2LIE is my amateur radio call sign, and this is session eight of the Scanner School podcast. In today's session, we're going to break down LTR trunking, what it stands for, how to monitor it, and what it's all about. So stay tuned.

Welcome to the Scanner School, a podcast dedicated to the scanner radio hobby. Class is about to begin. Here is your host, Phil Lichtenberger.

Welcome to our eighth session of Scanner School. I want to thank everybody who has listened or been there since the very beginning. Since we launched a little over a month ago, uh, for those of you who have probably binged on sessions one through seven, I want to thank you and if this is your first time listening to the Scanner School podcast, welcome aboard. You can reach out and actually join our Facebook group at ScannerSchool.com/FacebookGroup.

And we're right in the middle of a contest right now. And what happens with the contest is I'm giving away my time to three winners. What exactly is my time? My time is my consulting, that I'm kind of marketing right now. So basically I'm selling windows of time, 30 minutes at a time for you to ask me anything that you need help with, or say you've got a brand new radio and you're trying to set it up or you're trying to use a piece of software like Free Scan or Butel or Pro Scan and you can't seem to get it to talk to your radio. Uh, maybe you're in the market for something new and you're not exactly sure what to buy or what will work in your area. Maybe you have a question about setting up your antenna or getting something like that unit trunk to work. Um, maybe you just have a question about something very basic or, you know, something that's not too basic.

But, if you need help with scanning and you were looking for some one on one assistance, let me know. Go to ScannerSchool.com/contact. And that will take you to our email form where you can reach out and contact me and book an appointment. But we also have this as a Freebie for three winners and all you have to do to win a 30 minute session with me is go on our Facebook group and the link to that is ScannerSchool.com/FacebookGroup and leave us a question or a comment in the group and that's all you have to do to qualify. Anybody who has been a member of the group up until this point is registered automatically. And anybody who would like to be part of this contest must be a member of the group by the end of the day on February 28th, 2018. And the winner or the winners of the freebie contest would be announced on our eleventh podcast, which is going to be live on March 6th, I believe is the date on that one. I'll just check my calendar. Yes. March 6th will be the announcement on this podcast as to who wins the three sessions with yours truly. Uh, again, if this is your first time listening, I would love for you to join our mailing list, which is on the front page of our website at ScannerSchool.com. We also have a Facebook page which is at ScannerSchool.com/Facebook and uh, we're getting active on Twitter. So if you're on Twitter and you'd like to, uh, follow us and go back and forth of the conversation on there, we can do that. ScannerSchool.com/Twitter.

And again, this podcast is also available on iTunes, Stitcher, Google Play or directly on the website. So again, thank you everybody for being there and let's start talking trunking.

So I'm not going to lie to you guys. LTR trunking for me has been a headache to try and figure it out. It's really not that difficult to do but for whatever reason. For me, it just seems to be one of those trunking protocols that makes me have to stop and think for a second. Again, no real reason why, it's just a little different animal than what we're used to when we talk about EDACS or Motorola. And it's a little bit different than what I talked about last week when I did the introduction to trunking. Now if you've missed that session of the podcast, you can always go back and check out the show notes or get a direct download by going to ScannerSchool.com/Session7 and that'll take you right to the introduction to trunking podcast.

So what we've talked about in that one was basically that most trunk systems have a dedicated control channel and you can kind of put your scanner on that frequency. You can hear the data noise and the scanner will kind of tell you what's going on when you get to a trunk system that uses a dedicated control channel. Well, the difference really with logical control or logic trunk radio, LTR, is the fact that you really don't have a dedicated control channel. What you have is a sub audible tone that kind of gives out the trunking information. And you may only hear a tone burst every couple of minutes or so. That home channel or, or that controlled channel can be used as a home channel, so you can use that for syncing up with a network to know that it's there and it's transmitting, but you can also use that as a transmit channel and have a conversation with the other members of your talk group on that channel.

So let's back up one second here. And let's talk about the parts of an LTR system. We're going to talk LTR standard just to start because that is what most trunking scanners are capable of receiving. There's other protocols of LTR and we'll, we'll touch on those. But for now let's just talk LTR standard. LTR standard, like I said, is the dinosaur. It's one of the earlier versions of trunking, if not the first version of trunking. And it was developed some time in the 1970s. So what happens with LTR trunking is you have logical channel numbering. So what that means is you may have five channels in this trunk system and they are in the radio in a set way. So frequency one is channel one, frequency two is channel two, all the way up. Three, four, and five, how many there are in there.

Now this is just an example. One, two, three, four, five. Not to confuse anybody, but you don't need to go in numeric order. There's plenty of trunk systems out there that have channel one, channel five, channel nine, channel 11, channel 13, you know those kinds of things. The key here is whatever the logical channel number is, is the exact way it needs to be programmed in your radio. So I'm going to say that one more time. The exact way that the channel numbers are laid out in the system is the exact way that it needs to be programmed into your scanner. So if channel one is channel one in the system, it needs to be in channel one of that scanning bank. So on the older scanners that did LTR you had multiple banks. So let's say you had a bank of 100 in your particular radio. So either channel one would have to be channel one, channel 101, 201, 301, 401. The first number one channel in that bank would be channel logical channel number one. But I haven't confused you yet. Then uh, then we're doing pretty well.

If I did confuse you, let me know. Give me some feedback on the podcast. Let me know where I've lost ya and I'll be sure to, um, to answer your email, let you know. And again, you can always contact me using the contact form at ScannerSchool.com.

So on those radios that have specific hard coated channels in a memory bank, channel one's got to be in the channel one part of that bank. Again, you know, channel 1, 101, 201, 301 If your bank has 100 channels. If your bank would only have 20 channels in each bank than you would have to say, you know, channel 1, 21, 41, 61, that kind of a setup. So that said, you know, channel five would have to go into the fifth channel in the bank and Channel Ten will go on the 10th channel of a bank, so let's say it that way. So that x channel number in each bank. Hopefully that makes a little bit more easier to understand.

On the radios that use like the dynamic memory allocation is what Uniden calls it. Those would be like your BCT15X's, your 996XT's or the B2's, or that kind of product line. You have to set it up in the system and it asks you for the logical channel number when you program that radio, so you don't need to skip a whole bunch. You just program it in exactly how it is. So channel three, you put the frequency and this case is channel 1. The next channel, channel 3, we put that into is logical channel number three.

Okay, so that aside, we need to make sure it's very, very, very, very important that the channel numbers are in exactly logically. Okay? That's the key when listening to LTR. So what happens if you don't program it up correctly? Well, what's going to happen is when you're monitoring an LTR system and the trunk channel gives the direction for the radio to go to one of the channel, you'll see that your scanner's going to try to go that channel and if the frequency is incorrect, it just could go right back to the the control channel. So I keep using this word home channel. What is a home channel? So each talk group on the system can be dedicated to or assigned to a home channel. Okay. And like I said, every frequency in this system, it's not really a control channel, it's a shared channel. It does the controlling as a sub tone and then it's also a voice channel.

So you could have a pool of talk groups who have home channel five. So that means the fifth logical channel in the system or logical channel five is that talk groups home channel. You could have a bunch of talk groups who have maybe logical channel nine as their home channel. So those talk groups always listening to channel nine to find out where to go. Okay, so this is where, like I said, it's a little bit different than standardized trunking because it's a little little odd to wrap your head around, right? So you could have talk groups spread out over the system. All right, so not everybody is in one location looking for the conductor as we talked about in session seven to tell it where to go. There are little tiny conductors I guess on each repeater channel. And those little conductors will tell you either to stay or to go.

Okay. Now if it tells you to go, where's it going to tell you to go to? Well, on the LTR standard system is going to tell you to go to the go-to channel, which would be the next channel in line to go to. So it may say, okay, my home channel is channel five, I have to make a call, but channel five is busy well the conductor is going to tell you in the subtone okay, go to channel nine and you go to your go-to channel which is channel nine.

Okay. So how are the talk groups on an LTR system set up? Now this takes a little bit of visualization in your head. So what happens is you have a single digit followed by a hyphen or dash followed by two digits, followed by a hyphen or a dash followed by three digits. Okay, so what is that one by two by three digit called. So what you have is you have your first digit, which is a zero or a one, and that's kind of called your area or your area code. Okay? So why do you have an area code of zero or one. We're talking binary here. Right? And what happens is if you have 2 LTR systems that are in close proximity to each other, that might be sharing a frequency, one system will be assigned an area code of zero and another system might be assigned an area code of one, and you typically will not see a talk group of zero on a system. It has a talk group of one and vice versa. So basically what the zero and one is, it's your area code to define two different LTR trunking systems that may be on the same frequency or area. And that's written down as A, when you look at a talk group. The next two digits is your home repeater. So if you were on systems zero and your home repeat or channel was channel five, then your talk group would be 0-05. If you're on area zero and your home channel is channel nine, then your talk group would be 0-09. Okay. So you can see how we're starting to build a talk group and what each, uh, each character means. So that we got A-HH. Okay. So now we've got our one by two and now we need the by three, which is the last three digits of the talk group. And that's the actual three digit talk group number. It could be anything from 001 to 254. And when you write it down on a chart, the last three digits are typically GGG, so your total strength for an LTR talk group will be written as A-HH-GGG okay. That's the format. So you have the area code zero. A home repeater, in our example, zero five, and then our talk group, 1,2,3 for this example. So your total LTR talk group would be 0-05-123.

Okay. So that's the basic of LTR standard.

Okay. So we also have what's called an LTR net, and an LTR net is pretty much the same as an LTR standard when it comes to programming it in the radio. It's backwards compatible. And typically any scanner that can do an LTR standard could also trunk and LTR net is a little bit more um, underlying data when it comes to an LTR net system. Little bit more, um, uh, things going on behind the scenes. But what typically happens with an LTR net is you can string a couple of sites together, you can roam onto another network and you can then bridge the link between the roaming and your home repeater. So this allows you to kind of extend the footprint of your home area. Okay. So when it comes basically time to monitoring system, that's really what we just need to know. Uh, one of the real unique changes are, is if you have a talk group that's up above from 240 to 247, those are temporary ids on an LTR net system.

Okay. So then we got two more in here, we have LTR passport and multi net. Now LTR passport and multinet. You can't monitor them from a scanner. It's just, it's just not built into any scanner that's out there as far as the protocol goes. And I'm not really sure why. Maybe it's just, it's not that popular or it could be because they really didn't perform all that well. Uh, if you go online, there's actually a, a wikipedia page for LTR multinet and it's basically wikipedia.org. And just do a search for LTR multinet. And it talks about here, San Rafael, California police department system that was in use and in May of 1994, they, um, they brought in somebody to evaluate the system and they were told basically that they had to scrap it and start over again just to summarize everything. They were having some big problems with the system. So what ended up happening was they scrapped that, uh, that LTR multinet system and they went with a Motorola smart zone system. And we're going to talk about LTR, I'm sorry, smart zone systems in two sessions from now. I want to talk about EDACS before we get there.

So who really uses an LTR system? Since its not APCO-16 compliant as far as the main standard LTR systems, it can't be used or shouldn't be used for public safety. That's where LTR, I'm sorry, that's where LTR multinet came in, right? LTR Multinet was an APCO-16 compliance system because it had an active control channel that was always there on all the time. Right. But other than that, who's on an LTR system? It's basically used, at least in my neck of the woods, it's used for businesses — so taxi cab companies, oil deliveries, privatized ambulance transports are kind of used on an LTR system, schoolbus networks, those kinds of systems. Any basic, leasable talk group on a commercialized trunk radio system. Basically it's a radio shop that has a trunk system that has room on there for you to purchase a radio and rent a talk group on this way. You're not building your own network out. So if you had a organization that needed a large area, instead of building your own repeater network, you would just go to a local radio shop and they would lease you a talk group or two on a system. And it has been an LTR system is basically what's been going around in my area. Um, again, that's my, that's my area. There's other areas that have different setups and other than that, but um, the big two in my location that I'm in have been swapping out their LTR for DMR. And we're going to talk about Dmr and in a future episode, don't really have the episode number yet. I'm not planning ahead that well, but it is going to be part of this trunking conversation that you and I are having.

So let's quickly summarize an LTR system. If I've confused you, I apologize, but um, but we'll go through it again. So LTR is a logic trunk radio and that's what it stands for. It's a system that was developed in the late seventies, and I forgot to mention before it's by EF Johnson Company. Okay. So what happens with an LTR system is you have a, um, a group of frequencies that are set up in a logical channel number. Basically it's a, it's a group of repeaters and the repeater will either send out a quick, uh, idol burst or the sub tone would have the, the trunking information on it, and your talk group would be assigned a home channel or a home repeater to listen to, which is a numerical representation of that repeater in the logical channel numbering of the system. I know, a lot of acronyms, and I'm trying to get it straight in my head. So again, for example, you may have three repeaters on your network and let's just say it's repeater one, repeater three, repeater five, and those would be how you would program them in the exact order in your radio. Okay. Logical Channel One, logical channel three, logical channel five. Your repeater system would have an area code, either a zero or a one, and that's the first digit of the talk group. The second digit of the talk group would relate to your home repeater. So in our example, we have repeater one, repeater three, repeater five, one of those three repeaters would be your home talk group. I'm sorry, your home repeater and that would be the next two digits in your talk group ID. So if you're on repeater three, it would be 03. And then the last three digits of your talk group are the talk group of the system that you're, the group that you're a part of. So what happens when you key up a radio is you would either get the home channel if nobody's using it and everybody who is part of that group would hear you and if you were on a busy channel, the radio would know the next go-to channel and that's where you would then go to, to, um, to place your call and all the, all the other radios on, they wouldn't know that to go there as well because the control, I'm sorry, the home channel, uh, would let them know that there is activity now for them on their go-to channel.

So like I said, a little bit crazy, not as easy to wrap your head around as some of the more advanced technologies when it comes to trunk radio systems. And, uh, again, it's the dinosaur. So hopefully I didn't really confuse you too much when it comes to talking about logical trunk radio or LTR trunking.

This session of Scanner School is sponsored by EastCoastPagers.com. East Coast Pagers is a Unication, Apollo, and Swissphone dealer serving the US market. From one way numeric and alphanumeric to voice and P25 pagers, East Coast Pagers has you and your department covered. Check out EastCoastPagers.com for Unication G1, G4, and G5 products and accessories, all Unication G1 pagers ordered from EastCoastPagers.com will ship with a spare set of batteries and a spare belt clip, courtesy of East Coast Pagers, and all G4 and G5 orders will ship with a spare belt clip. From now until March 31st 2018, all G4 and G5 orders also include the P25 phase two upgrade free of charge. Remember, you gotta order these before the end of March to get your phase two upgrade included with your new G4 or G5 pager. Again, check out EastCoastPagers.com.

So I want to thank everybody who has submitted their feedback using iTunes and uh, uh, via email and also via the Facebook group. Again, you can get on our contest by going to Facebook, I'm sorry, scannerschool.com/facebookgroup. Leave a comment or post a question in there and I'll be sure to respond to you in the group. And again, the contest window for a free session with me for a 30 minute session runs from now until February 28th, 2018 and the contest winner will be announced on the March 6th podcast or the 11th session of Scanner School. So instead of bringing on questions and answers as I normally do, I'm going to change up the ending just a bit. What I like to know is if you have any suggestions for the podcast, whether it being the formatting or just the way I present anything or if you have any ideas for a guest to be on the podcast, please let me know.

I have a couple of guests who have been recording future episodes with me and we are working on the schedule to put them in and find time to, uh, to get their, their stories on the podcast, how they use scanners and, and that kind of stuff. But if you're interested in being a guest on the podcast, please reach out to me. I would love to, uh, to share your story with your fellow students. If you use these scanners commercially or if there's something that you are a, uh, an expert in, if there's something that you're working on that you may find that the scanner community would be interested in, whether it's software or product or something like that, we would love to have you on the podcast. So drop me a line at scannerschool.com/contact and um, we'll, we'll get you scheduled for the podcast. So again, I want to say to everybody, thank you so much for your support. Thank you so much for being there. And next week we're gonna talk about EDACS trunking and how to set up that and hope it's a little less confusing than what we talked about this week with LTR trucking. So again, I want to say thank you. Thanks for being there and, um, we'll catch you next week.

Thanks for listening to the Scanner School podcast. Visit www.scannerschool.com to access the show notes and bonus content.

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