Re: SETI Re: ET's problem with Doppler.


prewar (prewar@btinternet.com)
Sat, 11 Sep 1999 19:50:35 +0100


David Woolley wrote:

> > Because of this I would take a fair guess that ET will
> > sweep frequency +- some few MHz either side of the
>
> If we went that far off the hydrogen line we would almost
> certainly jam other radio users, probably including several
> satellites.

My point was that if ET transmits a few MHz either side
of 1420, he would do this to ensure that no matter what his/our
Earths/star system velocities, there would be a signal for us to detect
nearer to 1420. I therefore suggested that maybe we only need to
listen at 1420 and let him, 'drop into our laps', as I put it. By 'step'
changing his freq. he would in part, move closer to as. (not physically!!)
I never suggested that we moved many MHz away from 1420.....just
the contrary, in fact. It's his TX's that step moves, not our RX's. He
may not have the problem with his own satellites,
( if he has such things), that you mention we would have.

> ....................................; so compensating for
> source unknown Doppler elements can be done at the receiver without
> compromising detectablity, but sweeping all possible frequencies at
> the tranmitter will make detection difficult.

Again I wasn't sugesting that ET 'sweeps', but that he may 'STEP
sweep'. I also suggested that he may well vary his rate of sweepng.
Of course one doesn't get anything for nothing in this universe,
so my suggestion has flaws, which offset any gains, no doubt.
I just ponder on what ET may do to help in his detection.

Guess that he will use more than one TX, so he would have many
transmision options open to him. If he is funded by a NASA type
of organisation he may be retricted for funds for his SETI (!), but I hope
that his planet has a full commitment to letting us know he is around. :-)

> The other factor, of course, is that the neutral hydrogen line is
> a guess at the psychology of the sender.

Yes, I do not suggest that 1420 is a magic panacea to ET, but as
most folk seem to go down that road, as a beginner, I am right
behind! I ponder on what ET/we may be done to increase the chance
of success.

Regards.

albErT !!



This archive was generated by hypermail 2.0b3 on Sun Oct 10 1999 - 15:46:34 PDT