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#1
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Need help decoding rtty signal
There are four very strong signals here on the east coast of U.S.A., I here
them best after dusk. 3.084mhz 3.102mhz 3.126mhz and 3.132mhz Here is what I know, 1000hz center frequency 850hz shift 75baud / 13.3ms so it would appear The signal stops erratically on both space and mark tones. Also, at times the baud rate seems like it becomes very fast, perhaps double. I hear this same exact 'signature' signal in many places, on many bands, and can't seem to decode it with normal 5 level baudot programs. However, the signal doesn't seem to be ascii either. Anyone want to give a listen, and tell me what I need. Are they encrypted, or do I just need a different rtty-to-text convertor? TNX KD3SH |
#2
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You are right about the shift and keying speed (850 Hz at 75 baud). What
appears to be a doubling of the keying speed is actually Mark-Space reversals, still sent at 75 baud. The signal is not bulk encrypted but individual messages seem to be. The reversals are sent before the beginning of a message and again after the end of it. I also observed periods of unmodulated carrier sent between periods of reversals, probably while the operator changed tapes or loaded another message into the computer or crypto device. If I listened carefully, it seemed that the beginning of some messages contained a rhythmic pattern which lasted a few seconds. I looked for a frame pattern, out to 226.8 msec (the limit of my software) but found none, so this introductory pattern must be longer than that. Also I could find no frame pattern within the bits of a message (more evidence of encryption), out to 226 msec. The freqs you mentioned aren't listed in my 2003 Klingenfuss list of utility stations, so I guess it is a relatively new station. Have you checked the Worldwide Utility News (WUN) website?? (Sorry I don't have their URL.) Some of their monitors might be able to ID the station. (It's not in an exclusive Amateur band, so it's not a problem for me HI) 73, .... Martin VE3OAT IARU Region 2 Monitoring System Coordinator www.storm.ca/~iarumsr2 ("the intruder watch folks") gudmundur ) writes: There are four very strong signals here on the east coast of U.S.A., I here them best after dusk. 3.084mhz 3.102mhz 3.126mhz and 3.132mhz Here is what I know, 1000hz center frequency 850hz shift 75baud / 13.3ms so it would appear The signal stops erratically on both space and mark tones. Also, at times the baud rate seems like it becomes very fast, perhaps double. I hear this same exact 'signature' signal in many places, on many bands, and can't seem to decode it with normal 5 level baudot programs. However, the signal doesn't seem to be ascii either. Anyone want to give a listen, and tell me what I need. Are they encrypted, or do I just need a different rtty-to-text convertor? TNX KD3SH |
#3
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gudmundur wrote:
There are four very strong signals here on the east coast of U.S.A., I here them best after dusk. 3.084mhz 3.102mhz 3.126mhz and 3.132mhz Here is what I know, 1000hz center frequency 850hz shift 75baud / 13.3ms so it would appear The signal stops erratically on both space and mark tones. Also, at times the baud rate seems like it becomes very fast, perhaps double. I hear this same exact 'signature' signal in many places, on many bands, and can't seem to decode it with normal 5 level baudot programs. However, the signal doesn't seem to be ascii either. Anyone want to give a listen, and tell me what I need. Are they encrypted, or do I just need a different rtty-to-text convertor? TNX KD3SH You may need to look this up in the Klingenfuss Data handbook, many RTTY signals can be tuned in and received OK but are encrypted. There may be a copy of the latest edition in your library. |
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