archive: Re: SETI: Polarization Modulation

Re: SETI: Polarization Modulation

Lloyd Doering ( dewitt@bellsouth.net )
Fri, 04 Sep 1998 13:52:49 -0500

> >... I'm specifically wondering whether CW controlled circular
> >polarization, the direction and rate of change of polarization, could
> >be used to carry a complex signal.
>
> Rich Replies:
> It would be possible, If the transmitting station was spinning his
> antenna.

Could one not do the spinning electronically, by varying the ratio of power
applied to perpendicular and stationary dipoles? What about bandpass? In
comparison with AM/FM? Might not ET find such a method more economical of
the available spectrum? It just seems to me that not knowing anything about
the polarization of candidate signals received could be a significant
disadvantage. I'm no expert by any means, so I could be way out to lunch,
but I cannot imagine why a CW broadcast containing information carried only
by changes in polarization would have to eat up large chunks of spectrum.

There was something published a while back about astronomers studying the
effect of galactic gravitational fields on polarization, something about
gravitational manipulation of polarization.
Optical astronomers do a lot more with polarization. Why isn't it a
conventional means of modulation? Must be a reason!