I found an FSK signal I can't identify

[KE7IZL]

I live in Seattle, Washington. I often here these transmissions. You can hear them every day.They often fade which suggests ionospheric distortion of the signal, which means I'm not receiving it line-of-sight, but rather on ionospheric bounce, which means the source of the signal is quite some distance away, not right here in Seattle.

I can't figure out what digital mode it is. It's not anything I can decode on MultiPSK, but it sounds very similar to Pactor-1 ARQ. I received it last night at 12:20AM Pacific Daylight Time. I checked in on the signal again today at 12:18PM Pacific Daylight Time, and it was going then too (not sure if there were any breaks in the signal between last night and this morning though). However right now at 1:35PM Pacific Daylight Time, the signal is not going (or at least it is being silenced at my location due to ionospheric effects), nor is there any other signal in its place.

It seems to be a packet based digital mode. By its packet length it is definitely closer to Pactor ARQ, not Amtor ARQ. However it lasts a bit longer than Pactor. Also it it has an ACK waiting period that's much longer than ones like Amtor or Pactor who's waiting slot is barely wide enough to fit the ACK reply in. Several such reply packets could fit into the wait period in this mode. My first thought was maybe packet radio, but HF packet is 300 baud, but this sounded slower, like Pactor-1 ARQ in 100baud mode. So I took out MultiPSK and tried to decode it with it set to Pactor, but (as expected) it didn't decode it. The packet was just too long for a standard Pactor packet.

Also it wasn't in a ham band (at least not any that's used in the US), but had a center audio frequency about 1.4kHz when my Icom PCR1000 was set to USB and tuned to 13.055MHz (putting it's center RF at 13.0564MHz, well outside any ham band, at least in the US). Thus it's likely to be for some professional communication equipment, and may not be a standard mode for ham operation. I don't know what is being sent even (text, telemetry data, etc).

Here I've posted a download link to a zip archive containing three MP3 files. One is a recording I made of the signal I am talking about, and the other 2 are Amtor ARQ and Pactor-1 ARQ (which I downloaded from a radio sounds site, and then trimmed to make a reasonable length). These 2 files are just a reference to compare to the signal I recorded.
Unknown pactor-like FSK signal.zip

And here's a zip archive containing the spectrograms of each of the 3 signals that were in the above zip archive.
Unknown pactor-like FSK signal spectrogram.zip

I just looked at this FCC frequency table http://transition.fcc.gov/oet/spectrum/table/fcctable.pdf (accurate as of June 2 of 2011) and it seems that signal is in a band that is used in the US and internationally as a "maritime mobile" band. I often find strange signals such as this in various HF maritime bands. Unlike other unusual modes on these bands which you may hear once and never again, this one is one of the more common modes, but I have no clue what it is.

From spectrograms it seems to have a frequency shift of 100Hz. From running it through this neat audio software I downloaded called Analog Box (which lets you make tons of different DSP devices modulators, filters, etc using a "flow chart" like system) I managed to find out a lot more about the signal. It is 100baud, and each packet consists of 153 bits. It also keeps repeating the EXACT same pattern of bits, like a beacon, so it's unlikely that the waiting period is actually used for an ARQ ACK/NAK reply, but rather for some kind of connection reply to the beacon hardware from another signal source trying to connect to the beacon.

If someone can tell me what this signal is, I'll be really happy, because as much as I've analyzed it and tried to figure out what it is, I can't put a name on the digital mode that's being used, or even what it's being used for. I've been hearing it now for years on my ICom PCR1000 receiver and have no clue what it is. Any help here will be very much appreciated.

 

[ka3jjz]

Moved to our HF digital decoding forum...you might find this of interest

http://forums.radioreference.com/digital-signals-decoding/196111-multipsk-users-identify-modes.html

You've done 1/2 the work with getting the spectrograms - now it's time to look through all those links (not just the MultiPSK one) and see which graph corresponds with what you have.

best regards..Mike

 

[KE7IZL]

Thank you for thi info. unfortunately the spectrograms there are recorded at a different speed, with different color scheme, and with different sensitivity levels so by themselves they won't help. However I can also guarenty that none of the MultiPSK modes are the one I'm looking for. I've tried decoding with every FSK mode MultiPSK has to offer, in both the "professional" and "amateur" sections of modes in that program. I get nothing from any of the modes. It's therefore likely that it isn't a commonly used mode the world over, but may just be used in one part of the world. It would be neat if I could some how set up an HF Radio Direction Finder at a couple different locations and locate it by where the direction lines crossed, but that would require specialized equipment and software (and likely would cost more than I'd like to pay). At least though if I knew where it was coming from It would help me narrow down my Google searches by location.

 

[ka3jjz]

And nothing on the UDXF searching for 13055; interesting catch...

By the way, please use UTC (GMT) in all reports - that way everyone is looking at the same time zone...

73 Mike

 

[KE7IZL]

And nothing on the UDXF searching for 13055; interesting catch...

By the way, please use UTC (GMT) in all reports - that way everyone is looking at the same time zone...

73 Mike

Ok, though I don't know how to display UTC on my computer clock, so I specifically stated in my post what time zone I was using, which was Pacific Daylight Time so those who were reading it would know what time zone I was using. Then those readers seeing the post could perform the conversion themself.


As for the frequency in your book, anything near to 13055? I ask because this signal was received when my receiver was tuned to 13.055MHz. However the center of the audio of the signal (half way between the 2 tones) was about 1.4khz. When this AF is added to the frequency my receiver was tuned to, I get a true RF center of the signal of 13.0564MHz. With a separation of 200Hz between the tones, the tones are each 100Hz off from the center frequency. So the lower tone is at 13.0563MHz and the upper tone is at 13.0565MHz. So instead of 13.055MHz it may instead be listed in your book at any of these frequencies:
13.0563MHz (for the lower tone)
13.0564MHz (for the center frequency)
13.0565MHz (for the upper tone)
Also the spectrum software I was using to get these numbers (in the software GoldWave, an audio editor) seemed to not be 100% accurate so these numbers may be off by as much as 100 or 200Hz (would probably have been better off making the spectrum measurements in Spectrogram 16).
However, I'd expect it to show up in your book (if it does at all) at any number in the 13.056x MHz range (with x being any number being from 0 to 9).
Also it may not show this specific frequency but it may be a set of frequencies used for a particular purpose, within a range (say for example, 13.0MHz to 13.1MHz, or something like that). However while that specific digital mode is unknown to me nor what frequency range is designated for it, one thing I do know it it falls into a band (12.23MHz to 13.20MHz) that is designated for "maritime mobile" communication by the FCC in the US, and is also recognized as an international "maritime mobile" band.
http://transition.fcc.gov/oet/spectrum/table/fcctable.pdf

By the way, what book is UDXF?

 

[KE7IZL]

please delete accidental duplicate post

 

[KE7IZL]

I just realized the best way for you to get a sample of the audio, stream it online!
I have configured my copy of VLC media player to stream on port 12121.
For you to listen to it yourself, use your copy of VLC player (download a copy if you don't already have it). After you start VLC player, hit Ctrl+N to bring up the network stream receiver dialog. In the text box on that screen paste this http://76.104.145.19:12121/
Then hit click the play button on the dialog. The dialog box will close and the audio should start to play in a few seconds. If it doesn't, press press the play button now on the main player window. After a few seconds it should now start to play.

Don't use the above URL in a browser or it it will simply try to download the stream data directly into a file. It must be used in the VLC player to play.


Just a note of interest, the noise floor goes up at night it seems (or at least the signal strength goes down, due to poor ionospheric propagation characteristics, I would assume).

 

[ka3jjz]

The UDXF or Utility DXers Forum is a Yahoo mailing list that specializes in DXing utility stations (i.e. non broadcast, non ham or CB) including the digital stuff you've been working on. Here is the URL;

UDXF : Utility DXers Forum

It's a very popular group, and always very busy. Lots of information can be gleaned from here. I was hoping that someone else had picked up your mystery station and reported it, but unfortunately came up empty on a search.

73 Mike

 

[KE7IZL]

I've changed the streaming path now, so now in your VLC player you must use this new URL instead of the one in the above post:
http://76.104.145.19:12121/output.flv
That is so it is more likely to to be compatible with other software that might expect to see a file name in the path.

And now you can also "download" it in a browser (at least better than it did before)
Also if now if you do put it in your browser it will name it as output.flv (not just a random name) and call it an "octet stream". It will then start to download the live audio data and store it in an FLV file. This will continue indefinitely or until you stop the download or I stop the streaming server. If you do stop the download it will delete it, so to keep the recorded stream you must must make a copy of the downloaded file after it's downloaded as much of the live stream as you are interested in (in Firefox there's 2 files during a download, *.* and *.*.part, copy the output.flv.part file in this case). Copy and paste it into the same directory and it will add the word "copy" to the filename (or into another directory and it won't add the word "copy"). Then stop the download. Delete the word "copy" and any other additional text like ".part" that the browser may have appended to the file name. Now it should just say output.flv. This technique works in Firefox at least, not sure about IE or Chrome.
Once you have the FLV file, just play it in VLC player.

 

[KE7IZL]

Has anybody yet tuned into my live audio stream at http://76.104.145.19:12121/output.flv

 

[KE7IZL]

Right now at the time 7:02 UTC, and the signal in question is coming in loud and strong.

 

[KE7IZL]

Let me correct that to http://76.104.145.19:12121/output
I changed it again, this time due to the browser sometimes cutting the download of the stream off when I gave it a .flv at the end.

However the instructions given above with regard to downloading (as opposed to live listening) remain almost the same. Again you use the new URL but now the file name will be extensionless, and one will have a .part extension when downloading starts. Again you copy the one with the .part extension to make a duplicate, then stop the download and it will delete its temporary files, then just rename the file copy you made to output.flv (or whatever you want with an flv extension). Then you can play it in VLC player from the file (as opposed to loading the URL directly into VLC and playing it streaming as I talked about before).

However I have switched frequencies at the moment and am now listinging to XSL "slot machine" instead of the other mystery signal. Go here for that thread:
http://forums.radioreference.com/di...7943-wow-slot-machine-transmitting-again.html

 

[KE7IZL]

Just to let you know, I've stopped streaming for now. Also I won't post specific streaming info in threads about specific digital modes, as I may at any time choose to change the frequency, demodulation, etc that the radio is tuned to. Instead I'll later create a separate thread that explains how to listen to the live stream (so you can hear whatever happens to be on, and I'll also there likely announce what I'm listening to at any given time if I change it, as well as info whenever I start or stop streaming).

 

[SCPD]

13.055 is generally SITOR marine traffic.

 

[ka3jjz]

There is also a possibility that you could have run into a variant of PACTOR that Globe Wireless uses called GW-PACTOR - it's copyable by a couple of packages I can't remember off the top of my head, but there aren't too many that can do it. As GW is a huge maritime communications company it wouldn't surprise me in the least

best regards..Mike

 

[KE7IZL]

There is also a possibility that you could have run into a variant of PACTOR that Globe Wireless uses called GW-PACTOR - it's copyable by a couple of packages I can't remember off the top of my head, but there aren't too many that can do it. As GW is a huge maritime communications company it wouldn't surprise me in the least

best regards..Mike

WOW YOU WERE RIGHT! BIG THANKS!!!!!
I just found did a Google search for GW Dataplex (another name, and apparently the correct or more common name, for GW Pactor) and found this youtube video ‪Hoka Code3-32P: Automatic Classification of GW-Dataplex‬‏ - YouTube
When I played it back into my sound card (used Windows mixer set up to use speaker out as the input to monitor) I found that when I then used Argo to display a spectrogram that the spectrogram displayed from the Youtube audio playing is identical in appearance to the spectrogram that is displayed from me playing back the wav file of my "mystery" signal (except maybe for a few data bit differences from the result of it being from a different station, thus different callsign or station name being transmitted). I am now 99% certain that this was the digital mode being used in that signal, which makes it no longer a mystery

 

[KE7IZL]

From further googling, I found that it is also known as a "channel free marker".

Now my next mystery is that (though I don't have any recordings of it yet) I found that when people start transmitting on that frequency it sounds like narrow band noise bursts and the spectrogram looked something like a high speed PSK mode of some kind. I checked Pactor III spectrogram as I suspected it was a Pactor mode for a while, but none of the spectrograms I've gotten from any of the Pactor III submodes looks quite like the signal in question. I'll have to do more googling to find more info maybe.

 

[KE7IZL]

Transmission1 • View topic - Help to identify the mode 8.637 this forum post and the included zip file is more proof than ever before that it is GW Pactor/Dataplex that I've heard (he even has a wave file of his signal), though that high speed data burst you can hear near the end of that guy's wave file (just like what I've also heard periodically on the same channel as the FSK packets on my mystery signal) doesn't seem to be the same mode (though on the same channel) so is it a different sub mode of this GW Pactor / GW Dataplex?