Understanding Capacity Plus trunking

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Forts

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When this thread was started very little was known about Capacity Plus (and Connect Plus) let alone decoding them. The discussion was intended to me more technical in nature as we were trying to understand the inner workings and add our discoveries to DMRDecode.

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wildbillx

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Has anyone seen " Emerg Enc Bcast OVCM Group call; TG=133380 RID=525825 Ch=65535"
I figure it was some sort of emergency button activation. But have been sitting on the control channel with nothing for 2 hours until this.
 

CanesFan95

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So Forts, are you a firefighter with that gear showing in the pic? It's rare to find a firefighter with technical radio knowledge. Or even an interest, for that matter.
 

CanesFan95

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I would have thought UNDERSTANDING Capacity Plus would have meant something more like explaining...

Okay, so each frequency on a Cap+ system uses up 2 LCN's, similar to EDACS or LTR. They are called the 1/2 frequency, the 3/4 frequency, and so on. TDMA has 2 slots per frequency which are each one of those LCNs. etc...

See what I mean? That would be UNDERSTANDING Capacity Plus. I think the problem is, it's hard to find anything online that really explains how it works, for the everyday scanner listener.
 

Jay911

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I would have thought UNDERSTANDING Capacity Plus would have meant something more like explaining...

Okay, so each frequency on a Cap+ system uses up 2 LCN's, similar to EDACS or LTR. They are called the 1/2 frequency, the 3/4 frequency, and so on. TDMA has 2 slots per frequency which are each one of those LCNs. etc...

See what I mean? That would be UNDERSTANDING Capacity Plus. I think the problem is, it's hard to find anything online that really explains how it works, for the everyday scanner listener.
No, that's "TDMA for beginners". As Forts said, this thread was originally directed at a more technical audience.
 

garys

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Ok, DSD what can I do on Con+ to find the ghost freq?

What I have found works best is pretty time consuming. I set up one of my dongles using FMP24 and DSD-CC. I sit that on the control channel and watch for when it selects one of the missing frequencies.

I set the other dongle up using SDR# feeding DSD-CC. Then I scroll through the frequency band (in this case 93x.xxxx) looking for a frequency to pop up. I have no idea how I would do this if the system was UHF or VHF.

It's very time consuming. A month or so ago I was looking for two missing frequencies for a Con+ site. Over three days I spent about 8 hours sitting in front of my computer scrolling back and forth through the 93x trunking spectrum before I was able to confirm the frequencies.
 

natedawg1604

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What I have found works best is pretty time consuming. I set up one of my dongles using FMP24 and DSD-CC. I sit that on the control channel and watch for when it selects one of the missing frequencies.

I set the other dongle up using SDR# feeding DSD-CC. Then I scroll through the frequency band (in this case 93x.xxxx) looking for a frequency to pop up. I have no idea how I would do this if the system was UHF or VHF.

It's very time consuming. A month or so ago I was looking for two missing frequencies for a Con+ site. Over three days I spent about 8 hours sitting in front of my computer scrolling back and forth through the 93x trunking spectrum before I was able to confirm the frequencies.

With a little practice you should get more efficient. Also if you have a hardware scanner, you can run custom band searches and identify "new" DMR frequencies pretty quickly just by listening for the very annoying motorboat sound, it's pretty hard to miss.

In my experience, you will only have difficulty finding a "missing" DMR frequency if the system is not very active and doesn't generate idle messages. In that case, it may take a while to find missing frequencies, because you won't see/hear anything unless someone is actually talking on a radio. And, some DMR systems are only used by a few people who might talk on the radio once a day, or even once week. But if the system is fairly active it should be pretty easy to find missing frequencies under most circumstances.
 

adcockfred

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I can see with this 900 system I am just gonna have to get closer to the tower. You guys are invaluable when I can't see the trees from the forest.
 

EricCottrell

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What I have found works best is pretty time consuming. I set up one of my dongles using FMP24 and DSD-CC. I sit that on the control channel and watch for when it selects one of the missing frequencies.

I set the other dongle up using SDR# feeding DSD-CC. Then I scroll through the frequency band (in this case 93x.xxxx) looking for a frequency to pop up. I have no idea how I would do this if the system was UHF or VHF.

It's very time consuming. A month or so ago I was looking for two missing frequencies for a Con+ site. Over three days I spent about 8 hours sitting in front of my computer scrolling back and forth through the 93x trunking spectrum before I was able to confirm the frequencies.
Hello,

VHF or UHF is similar over a larger span of frequencies. The great thing about Connect Plus is the voice channels identify the system and site, then the main task is figuring out the LCN. With Capacity Plus, it is the other way around. You can easily figure out the LCN, LSN, etc., then the main task is figuring out what other frequencies go with the system.

73 Eric
 

garys

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I probably should have been more clear on delineating the two. Con+ is easier to figure out for the reasons you point out. As you know, in our general area the biggest Con+ network is on 93x.xxxx frequencies to the search range is very well defined. Easy being a comparative term since it's still time consuming.

The two most active Cap+ systems near me have fairly well known frequencies, but it still takes some time to figure out all of the information. Even more so since some frequencies appear dormant unless the system is very busy.

Hello,

VHF or UHF is similar over a larger span of frequencies. The great thing about Connect Plus is the voice channels identify the system and site, then the main task is figuring out the LCN. With Capacity Plus, it is the other way around. You can easily figure out the LCN, LSN, etc., then the main task is figuring out what other frequencies go with the system.

73 Eric
 

CanesFan95

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With a little practice you should get more efficient. Also if you have a hardware scanner, you can run custom band searches and identify "new" DMR frequencies pretty quickly just by listening for the very annoying motorboat sound, it's pretty hard to miss.

In my experience, you will only have difficulty finding a "missing" DMR frequency if the system is not very active and doesn't generate idle messages. In that case, it may take a while to find missing frequencies, because you won't see/hear anything unless someone is actually talking on a radio. And, some DMR systems are only used by a few people who might talk on the radio once a day, or even once week. But if the system is fairly active it should be pretty easy to find missing frequencies under most circumstances.

I think it's a lot easier to do limit searches on a tapped scanner to find missing frequencies and piece together a system. It is difficult and time-consuming, but I think a regular scanner will be faster and easier than trying to search with a dongle. A big problem here in the Tampa area is all the systems are DEAD. There's so little activity that it makes it hard to figure out a system.

This has always been a funny thing about Tampa. It's (supposedly) a major city area, but SMR-type radio systems have always been DEAD. Even back in the LTR days (which are still around, a little bit). Instead of having one nice big busy system, we have a lot of small crappy systems spread all over the place with light usage that makes it hard to figure out the frequencies.

But here's something I do, and you could try this. Use an Excel spreadsheet and log what you find. Include a column with what talk group IDs you see active on the frequency. Listing the TG IDs is what will clue you in as to which frequencies go together on the same system. The colors in the cells are how I identify frequencies that are part of the same system:

DMR Trunked Systems.xlsx

I have multiple submissions to the RR database, but the queue is so long I fear it could be months before they'll be posted.
 

cg

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If you use FMP24, you can watch a 2+MHz swath of the band for signals. After a bit you can learn to guess which spikes are DMR.

chris
 

adcockfred

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Taking the lap top closer to the tower worked for me.. But I was chasing missing freqs on con+ 900. Thanks, natedawg for slapping me up side the head!!!
 

DonnieDog

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Idea?

This idea may have been discussed but I couldnt find it anywhere.

Im trying to determine the LCN order of a Cap+ system here so this is my possible solution. The system has 10 frequencies under the license. I have determined the primary rest channel and the secondary.

Say I take one frequency at a time and enter it in the system lets say 20 times (by itself) all with LCN 1 to 20. Would it stop on the correct LCN# then when there is traffic?

You cant enter the same freq multiple times in the 436 by hand but you can through Sentinel.
 

adcockfred

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Yeah, I tried that approach with fmp but as it turned out I was not close enough to pick up those weaker channels. Dealing with 900 mzh con+ system.
 

JASII

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Understanding Capacity Plus Trunking

I just ran acroos this thread, so I am still coming up to speed on this. I have been an end user on a Capacity Plus system for over five years now. I recently bought a Uniden BCD325P2 and did the DMR upgrade.

-How much can I do with that to gather information on DMR systems in my area?

-So far, I have used Butel's ARC XT PRO to log as many DMR frequencies as I can in my area.

-I have also used ProScan, as well.

-I have been able to determine whether they are: DMR, CAP, CON, or XPT, when it displays.

-I have not ran across DT3 yet.

-I have determined/logged Color Codes for them.

Since there are only three XPT frequencies logged so far, I have reason to beleive that thee are all part of the same system, but I need to listen to them a bit more to confirm.

I have only logged two CON frequencies so far and I suspect that they are also a part of the same system as one another and that other connected repeaters are too far away for me to hear.

So, with that in mind, I will focus on the remaining frrequencies that are CAP. Some were easy to group together because they all were licensed to the same entity and were busy enough to hear all frequenices in a short period of time.

It is the rermaining frequenices that will be a challenge for me. Many of them seem to be licensed to Ancom, which is a local communications provider near me. My questions are as follows.

-Is there still a maximum of six repeater pairs in a Capacity Plus system?

-I gather that sometimes the repeaters have the same Color Code, but it is not always the case. Is that correct?

-If one repeater pair is Capacity Plus, must it always have at least one other associated repeater pair?
(Or, can ther actually be a one repeater Capacity Plus system?)

-With regards to FCC licensing, are most associated frequency pairs (for a give system) operating under the same license and call sign or are many systems comprised of a frequency pairs under differeing call signs?

-With regards to the "date burst" on the Capacity Plus repeaters, what is the longest I would have to listen before a given repeater would transmit a data burst? For example, if it is a six repeater CAP+ system, could as much as five minutes pass before the data burst changes to the next repeater in the rotation?
 

ngel

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2 Tampa bay area Capacity plus systems question

I think it's a lot easier to do limit searches on a tapped scanner to find missing frequencies and piece together a system. It is difficult and time-consuming, but I think a regular scanner will be faster and easier than trying to search with a dongle. A big problem here in the Tampa area is all the systems are DEAD. There's so little activity that it makes it hard to figure out a system.

This has always been a funny thing about Tampa. It's (supposedly) a major city area, but SMR-type radio systems have always been DEAD. Even back in the LTR days (which are still around, a little bit). Instead of having one nice big busy system, we have a lot of small crappy systems spread all over the place with light usage that makes it hard to figure out the frequencies.

system 1: https://www.radioreference.com/apps/db/?sid=8588
system 2: https://www.radioreference.com/apps/db/?sid=8562

I have been monitoring both of these Cap+ systems trying to figure them out. I have used my whistler 1080, DMRdecode and DSD+ fastlane.

What I have found is much difficulty figuring out how to program them as a trunked system on my whistler 1080, and what seems to be the systems not using all listed frequencies on the FCC database or here on radioreference.

With system 1, I can only pick up site 2 which is 462.3000 mhz. According to DSD+ it lists this frequency as Channel 1&2, Problem is there are multiple talkgroups active and it seems on my scanner it is not picking up all the slots correctly, I do have it set to receive any slot. The question i have is when i enter in the system should I be entering the trunked system as channel 1 462.3000 and channel 2 462.3000 or just only entering 1 frequency for this system as channel 1?

With system 2 I have been monitoring for several weeks and I only receive voice traffic or data bursts on 452.875, 451.975 ad 452.975. DSD+ is showing the the first frequency as 1&2, the second as 3&4 and the 3rd as 5&6. No matter how I enter the system in the scanner as a trunked system it will not follow correctly. Again am i to duplicate the frequencies when entering them into the scanner? Should I leave the rest of the listed frequencies that seem to be dead with no traffic out?

I know this is a software forum but I was directed here, thank-you for any help.
 

slicerwizard

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With system 2 I have been monitoring for several weeks and I only receive voice traffic or data bursts on 452.875, 451.975 ad 452.975. DSD+ is showing the the first frequency as 1&2, the second as 3&4 and the 3rd as 5&6.
Those are the logical slot numbers.


No matter how I enter the system in the scanner as a trunked system it will not follow correctly. Again am i to duplicate the frequencies when entering them into the scanner?
No, just enter them as channels 1, 2 and 3. Same idea with the first system.


Should I leave the rest of the listed frequencies that seem to be dead with no traffic out?
Shouldn't matter.
 
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