SDRTrunk MPT-1327

[kd7jfv]

I'm trying to follow a MPT-1327 system in Bend, Oregon on 161.800 mhz. I have entered all the data into the playlist editor, created a new channel. When I click PLAY nothing happens, play does not show up in the grid above, no data stream shows in the main window. I have attached screen shots. I have also downloaded two MPT systems from the radioreference.com interface and none of them work. SDRtrunk works great on P25 systems. Am I missing something?

 

[kd7jfv]

iCloud Photos - Apple iCloud
iCloud Photos - Apple iCloud

 

[DSheirer]

Are there any errors in the application log?

 

[kd7jfv]

Quite a few, the forums wont let me post

20240217 160706.523 [main] ERROR i.g.d.s.t.sdrplay.api.SDRplay - Unable to load SDRplay API library from default install path. Loading from java system library path [23MB/34MB 68%]

20240217 160718.739 [sdrtrunk cached thread 2] ERROR i.g.dsheirer.util.ThreadPool - Error while executing runnable in scheduled thread pool [sdrtrunk cached thread 2] [120MB/186MB 64%]

20240217 160719.172 [sdrtrunk cached thread 4] ERROR i.g.dsheirer.util.ThreadPool - Error while executing runnable in scheduled thread pool

20240217 160719.355 [sdrtrunk cached thread 5] ERROR i.g.dsheirer.util.ThreadPool - Error while executing runnable in scheduled thread pool

 

[kd7jfv]

I downloaded the latest beta v0.6.1-beta-1 and it is working on the MPT-1327.

 

[sonm10]

Try UniTrunker instead. I liked much better than SDR Trunk. However, the MPT-1327 system near me is transitioning to DMR tier 3.

 

[DSheirer]

@kd7jfv I think I just fixed that bug. If you try the nightly release.

 

[chrismol1]

I downloaded the latest beta v0.6.1-beta-1 and it is working on the MPT-1327.

Glad to hear its working. I use the nightly version and check all the time for a new version. There has so many updates recently its a good idea to use at least the latest release below that. So many updates to fix not only numerous issues but as well new features and many that improve the function. I'm greatly appreciative to Dsheirer & contributors.

 

[kd7jfv]

I've got it tracking the MPT-1327 system. Below are the channel numbers it's picking. How do I determine what the frequencies are? I've seen a few mathmatical formulas here on the forums but I'm not sure exactly what to do. Control frequency is 161.800 and the channels it has logged are 7, 215, 398, 430, 448, and 699. There are no FCC licenses for Pacificorp / PGE that I can find.


TIMESTAMP,DURATION_MS,PROTOCOL,EVENT,FROM,TO,CHANNEL_NUMBER,FREQUENCY,TIMESLOT,DETAILS
"2024:02:17:17:17:00","","MPT-1327","Call","559786"," (561697)","699","161.800000","","Invalid Channel Map - No Frequency For Channel 699"
"2024:02:17:17:21:54","","MPT-1327","Call","146090"," (140424)","430","161.800000","","Invalid Channel Map - No Frequency For Channel 430"
"2024:02:17:17:56:49","","MPT-1327","Call","4548"," (44)","215","161.800000","","Invalid Channel Map - No Frequency For Channel 215"
"2024:02:17:19:52:50","","MPT-1327","Call",""," (231715)","448","161.800000","","Invalid Channel Map - No Frequency For Channel 448"
"2024:02:17:19:57:21","","MPT-1327","Call","198675"," (201801)","398","161.800000","","Invalid Channel Map - No Frequency For Channel 398"
"2024:02:18:08:18:55","","MPT-1327","Call","17977"," (22407)","7","161.800000","","Invalid Channel Map - No Frequency For Channel 7"

 

[sonm10]

Is there a neighbor/peers list with associated channel numbers that can be associated with known frequencies? You can use that to calculate a band plan. Otherwise it will be difficult to figure out being that it is probably a custom band plan.

 

[kd7jfv]

Unfortunately no neighbor or peer list shown in SDRtrunk. :-(

 

[hiby99]

They use a market license Market license

ULS License - Part 22 VHF/UHF Paging (excluding 931MHz) License - WQNI865 - PacifiCorp - Map

 

[morfis]

Use the spectrum display of sdrtrunk to identify what frequency becomes active on a GOTO event. When you have a traffic channel identified monitor it for a while to look for a cleardown message which will show the channel number for the control channel. Then you'd have two known channel number/frequency pairs. That's enough to calculate the base frequency and thus the plan IF the system uses a logical plan. If it's a custom plan it will also be obvious and you will have to do the old fashioned thing and manually identify each channel using the spectrum method or a second scanner.

In the old days I used to use a second scanner to 'search' a couple of meg above control channels and that worked well.

 

[DSheirer]

An initial guess might be to use 150.0 MHz as channel zero or 149.9875 as channel zero and then calculate the other channels. This gives you a place to start watching in the spectrum to see if frequencies become active. You only need to confirm one of the channel number to frequency mappings to recover the channel map, if they're using a single, contiguous channel range.

```

Base​	0​	150​
​	7​	150.0875​
​	215​	152.6875​
​	398​	154.975​
​	430​	155.375​
​	448​	155.6​
​	699​	158.7375​
Control​	944​	161.8​

```

However, VHF frequency allocations normally don't align to a simple 12.5 kHz channel raster. So, you might find that they're using several channel ranges that overlap each other in frequency and where the base frequency for each range is offset from the others by something smaller than 12.5 kHz. For example:

```
0-299 - base 150.000000
300-499 - base 150.003125
500-699 - base 150.006250
700-899 - base 150.009375
```
You might focus on the cluster of channels (398-448) to see if you can recover those first. As soon as you find your first traffic channel, setup an MPT1327 decoder on that frequency so that during the next call you can decode the cleardown message that's transmitted at the end of the call, as @morfis said above. That cleardown message tells the radio to return to the control channel using the logical channel number for the control channel, and then you have your first (confirmed) channel number to frequency (161.8) mapping recovered.

Denny

 

[DSheirer]

Someone had the same question in the github discussions, so I created a FAQ:

FAQ

A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR). Website: - DSheirer/sdrtrunk

github.com

 

[morfis]

Quick example (when Denny was linking the FAQ!)

Constant data on the known MPT1327 TCC and probable traffic channel seen (I had already created a couple of decoders for suspected channels)


The suspected channel was indeed an MPT1327 voice traffic channel and shows a full cleardown message (note that some systems don't include the active channel number in the cleardown but you could have got that from the GOTO message on the TCC)




We now have two frequency channel number pairs.

Base Frequency = Frequency - (channels*channel step)

Assuming the channels are 12.5kHz (the most common)

Base Frequency = 181.9875 - (895*0.0125)
Base Frequency = 170.8

Check it with the other pair.

Traffic channel frequency = Base Frequency + (channels*channel step)
Traffic channel frequency = 170.8 + (671*0.0125)
Traffic channel frequency = 181.6875 : which matches what we saw in sdrtrunk.

That would be enough information to create a channel plan in the software IF the system uses a logical plan.

If the check had failed then you would know that the system was using a custom plan** and you'd have to keep repeating the identification steps to build up a full picture.



(** or far less likely, particularly these days, the traffic was from another MPT1327 system!)

 

[morfis]

...and with the details added to the channel plan (and a couple of alias entries just for fun)



Whilst sdrtrunk has a nicer interface and the simplicity of setup with sdrs, using Trunkview (here running on the same control data) makes it easy to see what idents are used for dispatchers and group calls plus also makes it easy to see when there are two different companies using the same prefix (relevant on this sytem if you look at prefix 040)

 

[Bowlieweekender]

Someone had the same question in the github discussions, so I created a FAQ:

FAQ

A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR). Website: - DSheirer/sdrtrunk

github.com

Guilty as Charged!

There have been two periods of activity today which I think must be conversations that originated on the 161.925 Control Channel. Suddenly a lot of digital hash came through the speaker so I rushed over to the computer and sure enough SDRTRUNK was showing:

"2024:02:19:15:07:26","","MPT-1327","Register","18007"," (8185)","","161.925000","",""
"2024:02:19:15:07:27","","MPT-1327","Command","8190"," (18007)","","161.925000","","Send Short Data Message"
"2024:02:19:15:07:58","","MPT-1327","Call","18006"," (22407)","280","161.925000","","Traffic Channel Grant"
"2024:02:19:15:07:58","45376","MPT-1327","Call","18006"," (22407)","280","161.925000","","Traffic Channel Grant"
"2024:02:19:15:08:50","","MPT-1327","Call","18006"," (22407)","280","161.925000","","Traffic Channel Grant"
"2024:02:19:15:08:50","45375","MPT-1327","Call","18006"," (22407)","280","161.925000","","Traffic Channel Grant"

In Events it showed:
002-0023 connected to 002-6023. Channel 280 and that was the same for both conversations, the only difference was the Frequency field showed 5.10675 the first time and 3.99817 the second. Thoughts?

Cheers Nigel

 

[Bowlieweekender]

...and with the details added to the channel plan (and a couple of alias entries just for fun)



Whilst sdrtrunk has a nicer interface and the simplicity of setup with sdrs, using Trunkview (here running on the same control data) makes it easy to see what idents are used for dispatchers and group calls plus also makes it easy to see when there are two different companies using the same prefix (relevant on this sytem if you look at prefix 040)

I've never heard of TrunkView, is this scanner discriminator-tap driven application and will it run on Windows 10 do you know?

 

[RMason]

I've never heard of TrunkView, is this scanner discriminator-tap driven application and will it run on Windows 10 do you know?

See - TrunkView :: MPT1327 Protocol decoder -

TrunkView is an MPT1327 protocol decoder, used in a single radio setup without the need for a discriminator output….

(I have no experience with it)