RE: SETI polarizatio; n modulation


Smith, S. Jay (sjs1@cdc.gov)
Wed, 2 Jun 1999 08:09:45 -0400


Is it possible to record a polarized carrier signal for subsequent decoding? Jay Smith/Atlanta > -----Original Message----- > From: Rich Tyndall [SMTP:nj1a@erols.com] > Sent: Tuesday, June 01, 1999 9:24 PM > To: seti@sni.net > Cc: Luisa Arruda > Subject: Re: SETI polarizatio; n modulation > > > ----- Original Message ----- > From: Luisa Arruda <luisa_arruda@hotmail.com> > To: <seti@sni.net> > Sent: Tuesday, June 01, 1999 11:37 AM > Subject: SETI polarization modulation > > > > > > > > Can anybody help us in our quest to understand the process of modulating > > e.m. waves by polarization, more specifically in the way that it was > applied > > in Carl Sagan's novel, "Contact". What kind of modulatores might have > been > > used, which frequencies are more practical for this modulation? > Mathematical > > fundaments based on Stokes parameters and Poincaré spheres - how are > they > > treated in this picture? > > > > Luisa and Paula > > > > Rich comments: > If you understand the basic concept of (RF) horizontal vs. vertical > polarization > or know how Polaroid sunglasses work, you can see how switching a carrier > source signal between modes can encode an off-on signal (like Morse code). > The same system would also work by switching between RHCP & LHCP modes. > If (linear wave) polarization was changed very fast, a good data rate > (like > RTTY?) > may be possible. > > Re: "Contact", > Seems to me, it was part of a 'test' to see if we could find the 'key' > hidden in the > polarization. (This kind of stuff makes SF more fun to read). > If one were going to try to contact a primitive planet (earth), they > (LGM) > (IMHO) would use the most simple mode possible. (Maybe CW). > As in, we don't use TV broadcast when we try to communicate with apes or > marine mammals. > Anyway, not too many reasons to use Pol-Mod in the real world. A video > signal > hidden in Pol-Mod might be easy to detect because it would most likely be > seen > as simple AM. > > That's my $.02 worth. > 73, Rich<> > > > > > > >



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