SDR# Monitoring and Decoding TIII (MOT) Help?

[T1000]

Hello community, nice to be here. I recently came in the radio world, i find it beautiful to play around. I have a RTL SDR V3 and started playing around with SDR# checking for signals in my arera. I found a DMR signal, always transmiting day and night non stop. Tried DSD+ on it and it says TIII (MOT) Site:L1-25 DCC:0 RAS NL:24 26
I see the terminal windows decoding something, i think only BS DATA, no voice activity at least the time i monitored it. Seems like a control channel. I need some suggestion and walkthroughs if possible what to do and how to get some voice out of this? Thanks in advance.

 

[pro92b]

It is a Motorola Tier 3 control channel. There is a database here on Radioreference that catalogs many systems. The frequency and location are needed to begin a search. If there is no entry in the database then a search on the FCC site may provide information.

 

[dave3825]

Your on a control channel that is also broadcasting there are 2 neighboring sites. If your in the US, list the state and county your in with the freq that your decoding.

If your feeding DSDPlus a control channel from Sdr#, I do not believe you will get voice. If you have DSDPlus FastLane, you can use Fmp24 to feed DSDPlus and it will steer to a voice channel when there is a voice grant using 1 dongle. I think the public version of DSDPlus might require 2 dongles.

 

[T1000]

It is a Motorola Tier 3 control channel. There is a database here on Radioreference that catalogs many systems. The frequency and location are needed to begin a search. If there is no entry in the database then a search on the FCC site may provide information.

I have searched the database and there is no record for anything in my country. What should i expect from monitoring the CC with DSD+FL? Voice activity i suppose. But if there is voice activity, what after that? I am reading a lot of articles in the internet but they say if you dont know the voice frequencies you cant find them. Any article how to step by step would be greatly appreciated. Thanks.

 

[T1000]

Your on a control channel that is also broadcasting there are 2 neighboring sites. If your in the US, list the state and county your in with the freq that your decoding.

If your feeding DSDPlus a control channel from Sdr#, I do not believe you will get voice. If you have DSDPlus FastLane, you can use Fmp24 to feed DSDPlus and it will steer to a voice channel when there is a voice grant using 1 dongle. I think the public version of DSDPlus might require 2 dongles.

I am not in US and no results on the database. I am using FMP24 with 1R.bat on DSD+ Fast Lane and getting this result as in the photo, but no other activity. What does this mean, there is no voice in the time monitoring or i am doing something wrong?

 

[mtindor]

I am not in US and no results on the database. I am using FMP24 with 1R.bat on DSD+ Fast Lane and getting this result as in the photo, but no other activity. What does this mean, there is no voice in the time monitoring or i am doing something wrong?

When voice activity occurs, on the main DSDPlus screen you will be given an indication that a voice call is active (and whether or not it is encrypted). Then watch your Channel Activity window and see what channels(s) pop up. You are going to have to know the other frequencies that are part of that site, or if you know the other active channel numbers from the Channel Activity window, it may be possible to calculate the frequencies associated with those channel numbers.

1. What is the current frequency you are monitoring?
2 . Have you ever seen the main screen report voice activity when monitoring that site?
3. Have you ever seen any channels indicated in the Channel Activity window when monitoring that site? If so, what channels?

Nothing is easy when figuring out DMR.

Mike

 

[pro92b]

With no database you are left to figure out the system on your own. In Tier 3 each frequency has a channel number which is broadcast. There are formulas to calculate additional channel once the channel number is logged. The screenshot you posted doesn't seem to show activity. What is the frequency of the L1-25 control channel? Can you tune around and try to pick up L1-24 or L1-26? The screenshot below
is an example of a working Tier 3 site here.

 

[mtindor]

There are formulas to calculate additional channel once the channel number is logged.

Not always. A DMR system does not have to have LCN<-->frequency pairing based upon a common bandplan.

 

[pro92b]

That's true in theory. I've surveyed a number of sites in the database and found none that are table lookup. All of them followed a common bandplan. If the OP can get channel numbers and frequencies for two or more control channels it will become clear if the usual formulas apply.

 

[T1000]

When voice activity occurs, on the main DSDPlus screen you will be given an indication that a voice call is active (and whether or not it is encrypted). Then watch your Channel Activity window and see what channels(s) pop up. You are going to have to know the other frequencies that are part of that site, or if you know the other active channel numbers from the Channel Activity window, it may be possible to calculate the frequencies associated with those channel numbers.

1. What is the current frequency you are monitoring?
2 . Have you ever seen the main screen report voice activity when monitoring that site?
3. Have you ever seen any channels indicated in the Channel Activity window when monitoring that site? If so, what channels?

Nothing is easy when figuring out DMR.

Mike

1-421Mhz
2-Not seen any voice activity till now.
3-No channel activity until now, only CC and a ?

 

[T1000]

With no database you are left to figure out the system on your own. In Tier 3 each frequency has a channel number which is broadcast. There are formulas to calculate additional channel once the channel number is logged. The screenshot you posted doesn't seem to show activity. What is the frequency of the L1-25 control channel? Can you tune around and try to pick up L1-24 or L1-26? The screenshot below
is an example of a working Tier 3 site here.

View attachment 149843

The CC is 421Mhz. There are no other transmitions around, i have checked. Will monitor a little more for voice activity, this transmition wasnt here a month ago so maybe they are still building it thats why no activity i think.

 

[dave3825]

2-Not seen any voice activity till now.

There are no other transmitions around, i have checked

When the cc is saying there is a voice call, somewhere there would be another freq active. How many dongles do you have?

 

[T1000]

When the cc is saying there is a voice call, somewhere there would be another freq active. How many dongles do you have?

Only one RTL SDR V3.

 

[T1000]

Only one RTL SDR V3.

I need some basic training. The CC signal i am receiving is transmitted from the repeater? Also the voice channels are transmitted from the repeater on other frequencies? Iam sorry but ia am a newbie and happend that the only station in my area is a TIII to start with lol. Do i need more than one dongle for this to work?

 

[Kazzaw]

No, if you are using DSD+FL you can use one dongle, the system just needs to be programmed with with frequencies.

The repeater will transmit the CC and any other voice channels. The best method I’ve come up with for tracking down TIII systems is view the regulator in your area for RF comms (FCC in US, ACMA in Aus, etc). Find the system location, view any licences and frequencies at the same site location. This might allow you to narrow it down to a certain amount of frequencies.

Once you know what frequencies to watch, keep yourself on the CC and watch for call activity. Some systems are rarely used, so you may be waiting a while. When you see a call grant on a channel, look at the other frequencies around you and see if you can identify one with a similar signal strength

 

[T1000]

No, if you are using DSD+FL you can use one dongle, the system just needs to be programmed with with frequencies.

The repeater will transmit the CC and any other voice channels. The best method I’ve come up with for tracking down TIII systems is view the regulator in your area for RF comms (FCC in US, ACMA in Aus, etc). Find the system location, view any licences and frequencies at the same site location. This might allow you to narrow it down to a certain amount of frequencies.

Once you know what frequencies to watch, keep yourself on the CC and watch for call activity. Some systems are rarely used, so you may be waiting a while. When you see a call grant on a channel, look at the other frequencies around you and see if you can identify one with a similar signal strength

Thank you, i inderstand. There is no regulatory system in my country that publishes the licensed frequencies. At least not in my knowledge. So the listing is off. It seems i will manually monitor the CC and see what i can do.

 

[dave3825]

Do i need more than one dongle for this to work?

No, if you are using DSD+FL you can use one dongle, the system just needs to be programmed with with frequencies.

When you see a call grant on a channel, look at the other frequencies around you and see if you can identify one with a similar signal strength

Once you have all the freqs entered in the frequencies file, you can listen with one dongle, provided that its not encrypted.
But, if the control channel does not populate the channel activity window with freqs needed, you would need another dongle or a scanner to discover them. I do not think TIII populates freqs from control channel data. If I am wrong, someone will correct me.

 

[Kazzaw]

You may get lucky with one dongle and see the channel grants in the same window as your FMP24 spectrum window and be able to work out the frequency that way.

I do not think TIII populates freqs from control channel data. If I am wrong, someone will correct me.

Usually no, it doesn't. Sometimes it does. I've seen it before on a Hytera TIII system, but its rare.

 

[Ubbe]

When it announces these sites 24 and 26 I believe they are active and would disappear if the site has no network connection. Try a better antenna and look between 420-423MHz. If you find another control channel, or you get a test call on a voice channel and have time to see what frequency it used, then it should be easy to find the LSN number for site 25 and enter in the DSD frequency table when using the LCN calculator. LCN to Frequency calculator for DMR TIII

/Ubbe

 

[merlin]

With no database you are left to figure out the system on your own. In Tier 3 each frequency has a channel number which is broadcast. There are formulas to calculate additional channel once the channel number is logged. The screenshot you posted doesn't seem to show activity. What is the frequency of the L1-25 control channel? Can you tune around and try to pick up L1-24 or L1-26? The screenshot below
is an example of a working Tier 3 site here.

View attachment 149843

I'm betting that is a multi site system and a busy one. I keep notes of sites I get. 2, TIII sites, and one not very busy.
The beacon is not very informative but does show neighbor sites. Looks like OPs site is a 3 site system, 24,25, and 26.
A handy display is the spectrum window. The white spectrum is 2 Mhz wide showing the current site.
The spike to the right is a NEXEDGE48 site. 2 to the left are other NEXEDGE48 sites.
using your pointer you can left click on one and it goes there.
With the spectrum active, you can just type in a frequency, enter, and you are there. IE: 460.18750 is the other TIII site.
Type that, and Viola.