Re: SETI: SAT Spread Spectrum indistinguishable from normal star? (was Re: Movie ;contact)

Philip Witham (
Wed, 29 Oct 1997 13:19:15 -0800 (PST)

> This is different; I'm saying that even with the key already in place at
> both ends, you need either perfect information through the channel (in
> both time and frequency domains) or *some* redundancy/pattern, however
> small; the latter permits you to resynchronize if that is needed.

Surely the sync signal would not have to be perfectly hidden to be
undetectable to us primitive apes? And, it is not actually needed, the
other method to recover the clock is brute computing force and a very
stable local clock. Just decode the signal using the key with all
possible sync timings, and when you find the correct timing, use from then
on. Or, be listening when the signal is first turned on.

> Another problem is that (I think) you
> have to be able to _resolve_ time to the granularity of the symbol rate.

This is, if I understand you, the main reason that I think an advanced
transmission would be invisible to us at our present state of
technology. See my prevoius post re: modulation bandwidth possible with
light -vs- current technolody.

> and I think the proposition is impossible to falsify, and more
> of a bull session topic than something to take action regarding: "What if
This IS a bull session, no? After all, we are talking about advanced
extraterrestrial data transmissions! Impossible to prove or falsify, but
what fun!