850 HZ RTTY--But Can't Decode

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KF4LYH

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Last night, I was scanning through HF and kept hearing what sounded like 850-hz RTTY. It must have been on 10-12 different frequencies. I think I heard it on 3.925 and 6.750, but whenever I try to decode it I can never seem to decode it. I have tried MixW and Fldigi. I was connected online to a SW Receiver using SDR-Radio (this program also has built in tools to decode some digital modes but no luck).

850-hz shift will almost always line up with the two lines on the waterfall, and I have tried speeds from 45-300 baud, but still no luck I did not get any legible text.

Has anyone been able to successfully decode these 850-hz RTTY signals? They seem to be all over HF.
 

Token

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850 Hz FSK is almost always military, most often US mil, and that means it is almost always encrypted. Not gonna do much with it. Yes, you will find it up and down the entire HF range, however I would be suspicious of the 3925 kHz freq, that is the 75 meter ham band and I don’t think I have seen 850 Hz mil RTTY intruding the ham bands very often.

What node on SDR-Radio.com were you hearing this on?

T!
 

KF4LYH

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That's What I Kind Of Figured

After I posted it, I looked around some more and found that most of the RTTY outside of the Amateur Radio bands is encrypted. I did also see that there is some unencrypted 450-hz shift RTTY out there, I believe I read that the Coast Guard does some weather reports on RTTY.

To answer an earlier question, I am pretty sure that I heard one of the signals within the 75 meter band. The node that I was using was a receiver in Fairdale, Ky. Anyways, thanks for the responses.

73's
 

Token

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As I said before, 850 Hz shift is almost always military, and almost always encrypted. Other shifts are more likely to be found unencrypted.

I do not think I have ever seen 850 Hz shift inside the 75 meter ham band, but anything is possible.

By the way, how are you reporting the frequency, is it center frequency, or is it tuned frequency? If tuned freq, what mode? Both methods are fine, but if center freq it is usefull to include c/f as a comment (example 6750 kHz c/f). Also, to report freqs are you just rounding them off? I noticed you said 6750 and 3925, and they are both to 25 kHz steps, was that the real freq? For example, I can find 850 Hz shift FSK logged in the past at 6750.4 kHz, 6751.5 kHz, and 6752.9 kHz, and right this minute I see some on 6763.5 kHz c/f.

T!
 
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