Marine Decode Question - DSD+ FMP24 Fast Lane 2.155

[AB9NN]

Trying to monitor this frequency via FMP24.ScanList:
156.300 FM BW=12.5 DELAY=10 Ch 6 Intership Safety

Using this batch file:
C:\_Files\SDR - Software Defined Radio\sdrsharp-x86\dsd+FASTLANE-FMN Scanner\Z - SCANNER 2
TIMEOUT 2
START FMP24 -i3 -o20003 -P0.0 -s1
TIMEOUT 3
START DSDPlus -e -fa -i20003 -m1

Commentary
-m1 seems to work. If have a NOAA Weather Radio frequency in the list it correctly routes analog audio to the speakers and is clear and strong. When it reaches the above frequency I hear digital sounds - a long stream - through the speakers. This leads me to some questions:
1) On the Great Lakes - specifically Lake Michigan - what sort of modes do ships run?
2) Is there any error in my code that would lead to a non-decode?

 

[DaveNF2G]

Analog FM voice.

 

[AB9NN]

That's what I thought but it's been a long time since I monitored. So - on that frequency, unless it's shared - what would the digital be? It seems some of the frequencies have been re-assigned to commercial pagers and such. Surprised they are not digital by now. In Outagamie County, WI the story was that they had to go digital by a certain time frame or lose fed money.

 

[slicerwizard]

Is there any error in my code that would lead to a non-decode?

Probably not, but why would whatever you're receiving be a digital voice mode that DSD+ can decode? I don't recall anyone reporting D-Star, Fusion, NXDN, P25 or ProVoice voice traffic on marine channels. Certainly not impossible, but I doubt it's legal.

I could see you RXing digital trafffic relating to Digital Selective Calling (DSC) / Global Maritime Distress Safety System (GMDSS) / Digital Automatic Identification System (AIS), but none of that is voice.

 

[AB9NN]

GMDSS is a strong possibility. Thanks. I use the -e parameter so, since I still hear the signals they must either not be encrypted or are encrypted with a method or form that the software doesn't recognize. Is there some other way to lock them out or mute them and yet allow voice through - either analog or digital? I am already using -e and -m1.

 

[dave3825]

How strong is the signal on 156.3? Could you be receiving a harmonic from another band? What does it look like in the sdr# waterfall?

 

[DRL-XM43]

GMDSS is a strong possibility. Thanks. I use the -e parameter so, since I still hear the signals they must either not be encrypted or are encrypted with a method or form that the software doesn't recognize. Is there some other way to lock them out or mute them and yet allow voice through - either analog or digital? I am already using -e and -m1.

If you are listening to digital data frequencies they are not decodable so -e is only useful to prevent DSD+ decodable but encrypted voice from hitting the speakers with garble.

The -m1 switch is designed to allow clear voice FM / AM pass through to the speakers so you can scan a mix of decodable digital and clear voice transmissions.

If you tune to non voice digital data streams you will get what it is -- a rude noise. The solution is not to tune to them?

 

[DaveNF2G]

There are decoders for GMDSS. I don't remember which channels are designated for it, but that information should be fairly easy to find.

 

[dlwtrunked]

Trying to monitor this frequency via FMP24.ScanList:
156.300 FM BW=12.5 DELAY=10 Ch 6 Intership Safety

Commentary
-m1 seems to work. If have a NOAA Weather Radio frequency in the list it correctly routes analog audio to the speakers and is clear and strong. When it reaches the above frequency I hear digital sounds - a long stream - through the speakers. This leads me to some questions:
1) On the Great Lakes - specifically Lake Michigan - what sort of modes do ships run?
2) Is there any error in my code that would lead to a non-decode?

Analog (non-digital) unencrypted FM voice only. Traffic is usually quite light except near significant ports.
There is digital data on 161.976 and 162.025 called AIS which is similar (but different from) APRS.
Google AIS decoder to get information including free decoders. Note though that as most ships are low, little will be decoded inland.

 

[slicerwizard]

GMDSS is a strong possibility. Thanks. I use the -e parameter so, since I still hear the signals they must either not be encrypted or are encrypted with a method or form that the software doesn't recognize.

Encryption has nothing to do with it. How would DSD+ even know if an unknown signal was encrypted? Monitoring mode 1 says monitor if no sync and signal present. The program doesn't see any recognizable sync patterns, so it unmutes, same as it does for any unrecognized signal. Doesn't matter if it's NOAA voice, SCADA data, whatever...

Is there some other way to lock them out or mute them and yet allow voice through - either analog or digital? I am already using -e and -m1.

No. It's just going to look like analog voice to a decoder that doesn't know how to decode it.

 

[AB9NN]

Encryption has nothing to do with it. How would DSD+ even know if an unknown signal was encrypted? Monitoring mode 1 says monitor if no sync and signal present. The program doesn't see any recognizable sync patterns, so it unmutes, same as it does for any unrecognized signal. Doesn't matter if it's NOAA voice, SCADA data, whatever...

No. It's just going to look like analog voice to a decoder that doesn't know how to decode it.

I thought DSD+ might know something about it based on the contents of the DSDPlus.txt file included with FastLane 2.155.
- " -e Auto-mute encrypted voice"

I agree that if it is an undefined transmission type to DSD+, as I suggested in prior posts, it would not know if it was encrypted or not. My comments were meant to cover both possibilities - it was an unknown transmission type and the -e would not work or it was known and the -e is being used and there may be some syntax error that I made in coding the start command line in the batch file. I agree - probably a pager or something and DSD+ doesn't understand it so it just forwards it to the speakers.

 

[DRL-XM43]

It helps if you ID the frequency first. You may want to try Artemis signal identifier.

There are many decoders for many signal types, it is clear what DSD+ decodes.

Yes if you are tuning unknown signals through DSD+ it will simply pass the raw signal noise to the speakers as it was instructed by the -m1 switch, which is designed to operate with only DSD+ appropriate digital transmissions or verified clear AM or FM voice transmissions.