SDR# Monitoring and Decoding TIII (MOT) Help?

[mtindor]

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

Just curious -- did yu purposefully not include the full frequency and instead just say it is in the 421 mhz region? Or are you saying the actual frequency is 421.0000? If the former, why are you obscuring the frequency? There is a reason people ask information like I've asked.

 

[T1000]

Just curious -- did yu purposefully not include the full frequency and instead just say it is in the 421 mhz region? Or are you saying the actual frequency is 421.0000? If the former, why are you obscuring the frequency? There is a reason people ask information like I've asked.

I am obscuring the freq by a little bit, i just dont know to whom it might belong and thought of that. Is it a problem?

 

[mtindor]

Looks like OPs site is a 3 site system, 24,25, and 26.

Why only three sites? Just because the current site is 24 and only lists 24 and 26 as neighbors? I'd think there are many more sites as part of that system.

 

[mtindor]

I am obscuring the freq by a little bit, i just dont know to whom it might belong and thought of that. Is it a problem?

It isn't right now, but if you find an additional site belonging to the same system and you want help determining LCN<-->frequency pairings, then whomever you ask to help with it is going to want to know the precise frequencies.

Might be some law that states you aren't allowed to monitor something, but is would there really be some law in your country that says you can't post a simple number? LOL. I guess in some archaic country it might be possible for you to post 421.2125 and have somebody to haul you off to jail for ten years. In any civilized country I don't think there would be any sort of issue posting a simple frequency. It's up to you though. Just keep in mind that when it comes time to ask for help calculating LCN<-->frequency pairings, if you don't do it yourself and you ask somebody here you will have to cough up the actual precise frequencies.

Mike

 

[T1000]

It isn't right now, but if you find an additional site belonging to the same system and you want help determining LCN<-->frequency pairings, then whomever you ask to help with it is going to want to know the precise frequencies.

Might be some law that states you aren't allowed to monitor something, but is would there really be some law in your country that says you can't post a simple number? LOL. I guess in some archaic country it might be possible for you to post 421.2125 and have somebody to haul you off to jail for ten years. In any civilized country I don't think there would be any sort of issue posting a simple frequency. It's up to you though. Just keep in mind that when it comes time to ask for help calculating LCN<-->frequency pairings, if you don't do it yourself and you ask somebody here you will have to cough up the actual precise frequencies.

Mike

Good point. Thanks Mike. Will keep this in mind.

 

[T1000]

Good point. Thanks Mike. Will keep this in mind.

I have a question. Playing around the freq to find the other sites, in SDR# i changed the sample rate from 2.4 to 3.2 and suddely i can see 3 very weak DMR signals around the freq i have. But i cant pick them on FMP24. Are they real or SDR# is playing games?

 

[dave3825]

in SDR# i changed the sample rate from 2.4 to 3.2 and suddely i can see 3 very weak DMR signals around the freq i have. But i cant pick them on FMP24. Are they real or SDR# is playing games?

What is your gain set at in Sdr#? Ideally you want to find a signal and increase the gain to where the signal reaches its highest point, and right where the noise floor just starts to rise. Same in Fmp24.

 

[T1000]

I am using the half bar of gain. I think 29 maybe. Can i set the sample rate to 3200 on FMP24 just to test it?

 

[dave3825]

Can i set the sample rate to 3200 on FMP24 just to test it?

Pretty sure Fmp24 only allows up 2.4

; sampling rate (1.0, 2.0 or 2.4)

 

[T1000]

I cant see the other sites from home and the antenna i am using. Only site 25 with a very strong signal but there is no voice activity until now.

 

[Ubbe]

I have a question. Playing around the freq to find the other sites, in SDR# i changed the sample rate from 2.4 to 3.2 and suddely i can see 3 very weak DMR signals around the freq i have. But i cant pick them on FMP24. Are they real or SDR# is playing games?

I think I saw the same thing happening with a RTL-SDR dongle that 2.4 where the highest possible sample rate in SDR# and going higher up to 3.2 it introduced a lot of false signals. I don't see any difference in signal detection between 1.024 and 3.2, it just shows a wider frequency range.

I usually have gain set to 34 in SDR# but going 40 and above will also start to introduce a lot of false signals. Having gain at 29 in SDR# seems way too low but it is dependent of the general signal levels from the antenna, lots of local transmitters and no filtering will need you to use a lower gain.

/Ubbe

 

[T1000]

I finally got some activity here. There were 3 short group calls today. 3 new radio ids and one group id. I got the channel number but no frequency was on the channel window. Is it possible to calculate the frequency? How?

 

[T1000]

I am seeing the post with the LCN to Frequency calculator i looks noce but i dont know the CC Channel, it has a ? In the window. I can see the neighbors sites CCs but not the one i am tuned in.

 

[Kazzaw]

The CC channel is the channel you are currently on. When you see group calls show up, you need to look for activity on the spectrum. This will give you a frequency to go with your channel number. Once you have one confirmed frequency and channel number, you can calculate the rest

 

[T1000]

The frequency calculator needs the CC Freq, the CC channel number and the target channel number to calculate the freq?

 

[Ubbe]

It would help if you state your exact CC frequency and voice channel number. Systems usually are set up with channel numbers and frequencies increasing from the CC and up thru the voice channels.

If the voice channel where somewhere around 1000-1200 and probably would be in the 421-422MHz range then the other sites 24 and 26 are in the 423Mhz range. But if the voice channel where up in the 1800-1900 range then the other sites CC are also in the 421-422 range.

The base frequency, channel 0, are usually an even round number when the system use that high channel numbers. Try using 410.000 as ref frequency and ref LSN as 0.

/Ubbe

 

[cg]

If the channel numbers are something simple like 3, 5, 7 then likely no bandplan and you will have to find all the frequencies by matching up activity (spikes in the FMP24 window), with a channel. In the FMP24 window, hit the "m" key. That shows activity for the range that is visible. and is sometimes helpful for finding the voice channels. Trial and error is sometimes how it works.

I would start populating the system in the files now. There are several files needed to follow a conversation as it switches between frequencies.

DSDPlus.NETWORKS gets an entry like:
TIII, 1, "unknown TIII system"

DSDPlus.SITES would be something like:
TIII, 1, 24, "unknown 24"
TIII, 1, 25, "Local site"
TIII, 1, 26, "unknown 26"

DSDPlus.FREQUENCIES would be a bit trickier as you have unknowns. Put your frequency where 421.ABCD is, put your voice slot number where @@@@ is. Each numbered voice slot gets a line. If you have adjacent numbers such as 697 and 698, only the lower one is used.
TIII, 1, 25, ?, 421.ABCD, 0.0, 0
TIII, 1, 25, @@@@, ???.????, 0.0, 0