At 11/4/2011 12:57 PM, Greg Ihnen wrote: >They both have separate feeds. The folks doing OSCAR feed the two >antennas with splitters and phasing lines to feed the same signal to >both antennas. To achieve the phase shift some use the antennas in >the same plane and feed them out of phase with phasing lines. >Another approach is to feed them in phase but shift one antenna >forward or back. Either way produces circular polarization. But the >key part of the OSCAR operation is the same signal goes to both antennas.
I used OSCAR 7 a little bit back in the late 1970s, and IIRC I had one of the cheaper approaches. I think I had an antenna that put 2 meters and 70 cm antennas on the same mast, cross-polarized to each other. The theory was that your echo to yourself would be roughly the same, whether you had the receiver or transmitter out of polarization with the bird. Of course if you were talking to somebody else, you'd potentially be out of phase... So yes, two antennas for CP, but one feedline to the transmitter, what today we'd call one chain, and a phasing harness. >Obviously with the MIMO stuff it's independent signals to each antenna. For an old timer like me, MIMO is still black magic. >Greg >On Nov 4, 2011, at 10:45 AM, Fred Goldstein wrote: > >>No. The OSCAR circular-polarized antennas had a feed split between >>the V and H antennas, which each had a driven element. The MIMO >>ones have independent feeds. -- Fred Goldstein k1io fgoldstein "at" ionary.com ionary Consulting http://www.ionary.com/ +1 617 795 2701 -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
