[RTTY] The Case for QYF (was We Need a New Strategy)

[Kok Chen]

On May 13, 2012, at 4:44 PM, Richard Schumann wrote:

> Say, don't RTTY sigs have a 'fingerprint' just like the human hand?

In addition to the baud rate and Mark duration at the beginning and ending (like a squelch tail) that I mentioned earlier, the shift frequency can also be different.  If this can be accurately measured, it might be able to narrow down the rig (FSK) or sound card clock (AFSK) that is used.

RTTY signals (both FSK and AFSK) also have different rise and fall times when they switch between Mark and Space: so the precise shape of the keyclick spectrum can also help to "fingerprint" a signal.

With AFSK, you can try to look for the suppressed carrier/sideband.  That will also tell what the exact Mark tone is used (although this won't be fixed if the culprit is using agile tuning by changing tone pairs on the fly).

By convention, RTTY signals come up in Mark state.  The rise time from no signal all the way to a full Mark signal (and probably accompanied by a slight ringing) is another fingerprint.

However, a true sociopath will then fake these parameters too.

Reminds me of the Spy vs. Spy stuff in Mad Magazine :-).

73
Chen, W7AY