Unreadable RTTY

[KE7IZL]

This is clearly an 850hz spaced RTTY (appears to be 75 baud) signal but no matter what settings I use for baud rate in MultiPSK, and no matter what polarity normal or reverse I use, and even after switching to MixW and using their 4 different varieties of ASCII RTTY (as opposed to Baudot, as ASCII RTTY's spectrogram seemed to more resemble the spectrogram of the signal in question than the Baudot RTTY spectrogram did), I can't get any readable text. It looks like just random decoded text like someone just was mashing keys on their keyboard while transmitting the RTTY. I made a recording in an MP3 file and also took a screen cap of Argo's spectrogram of the signal. Is there anything else that would look so similar to 850hz spaced RTTY that it could be mistaken for RTTY? I made my recording and spectrogram at 22:00 UTC. I've put them in a zip file and uploaded to Mediafire. Here's the download link.

Unreadable RTTY.zip

 

[kruser]

This is clearly an 850hz spaced RTTY (appears to be 75 baud) signal but no matter what settings I use for baud rate in MultiPSK, and no matter what polarity normal or reverse I use, and even after switching to MixW and using their 4 different varieties of ASCII RTTY (as opposed to Baudot, as ASCII RTTY's spectrogram seemed to more resemble the spectrogram of the signal in question than the Baudot RTTY spectrogram did), I can't get any readable text. It looks like just random decoded text like someone just was mashing keys on their keyboard while transmitting the RTTY. I made a recording in an MP3 file and also took a screen cap of Argo's spectrogram of the signal. Is there anything else that would look so similar to 850hz spaced RTTY that it could be mistaken for RTTY? I made my recording and spectrogram at 22:00 UTC. I've put them in a zip file and uploaded to Mediafire. Here's the download link.

Unreadable RTTY.zip

If I'm not mistaken, almost all RTTY is encrypted these days if it is outside the amateur bands. Even the typical weather stuff we used to all monitor on our expensive decoders has gone bye bye.
There is a german wx station still sending clear text rtty with much in english even but I'd have to find the freq's. I know an issue in the last 8 months or so of Monitoring Times had the station listed. The main topic of the column for that month was the fact about almost all rtty being encrypted these days. That was why they had reason to list the german station so users could at least try for something outside the ham bands.
I picked up the station and decoded it before but the signals here were always poor so I've given up months ago. I do still run some of the clean sounding signals through a hardware decoder or multipsk in hopes of finding something in the clear but never works any longer

 

[KE7IZL]

Wait, WHY is it encrypted? I mean it's in the marine HF bands so it's either ship to ship (much the same way truckers use CB) or land to ship (port and weather communications). And I can't imagine that any of the above communications is "classified". So why the encryption?

 

[kruser]

Wait, WHY is it encrypted? I mean it's in the marine HF bands so it's either ship to ship (much the same way truckers use CB) or land to ship (port and weather communications). And I can't imagine that any of the above communications is "classified". So why the encryption?

All good questions and the same I asked myself.
I wish I had a good answer. I've often wodered if perhaps they just moved most of it to another format (still on hf) or is it all going over the birds these days. Seems pretty stupid to encrypt a wx broadcast though. I can still hear voice wx broadcasts in the clear!

Please do post back here if you learn anything. I'll do the same.

 

[brandon]

They are military.

 

[ka3jjz]

A frequency would be a nice addition here, but yes, most of this 850hz shift stuff that looks like 75baud is assumed to be NATO or military. Sadly there's a LOT of that around, and you need to be something of a detective to find the readable stuff. Spend enough time chasing digitals, and you will be able to identify that sound just by ear, not needing a spectrogram...

73 Mike

 

[KE7IZL]

I have MixW which has many options for RTTY including some combinations of options that MultiPSK doesn't have, such as 7 and 8 bit ASCII using 850Hz shift (in MultiPSK is only allowed on Baudot RTTY, and even then only when baud rate is >= 50). I tried to generate signals using random characters for the text and using the 75baud and 850Hz shift, then tried Baudot and then the 4 ASCII modes (7bit ASCII, 8bit ASCII normal mode, 8bit ASCII with MSB cleared, and 8bit ASCII with even parity). Of these modes the ASCII ones made a spectrum that most resembled the signal in question, but the spectra between the different modes is almost impossible to tell apart. But I can be almost 100% sure that the mode being used in question is an ASCII mode. However trying to decode it with any of the ASCII modes in MixW also results in garbage text. However when trying to decode, after using 4 ASCII modes, and normal and reverse frequency polarity (8 different combinations of settings) it still resulted in garbage text. Now that's either encrypted, or using settings not supported by even by MixW (such as different numbers of start and/or stop bits, odd parity instead of even parity, etc). I only wish there was some program that allowed more complete control of the decoder's specs so more settings would be available. Would also be nice if the program supported on-the-fly decryption of received text using common algorithms (256bit AES, 128bit AES, DES, Triple DES, Blowfish, and even simple Password XORed with Text) so one could try to GUESS the decryption and decode the text (sort of like in movies where someone knows that some gov official's son "means everything to him" and so they guess the official's son's name is the password, and successfully decrypt the hidden message).