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

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

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.