Roy Lewallen wrote:
The sum of LHCP and RHCP fields of equal magnitude
is a linearly polarized field. The orientation of
that linearly polarized field depends on the
relative phases of the LHCP and RHCP fields.

....and...

Walter Maxwell wrote:
Without giving the problem any serious mathematical
or physical thought, only knee-jerk intuition, IMO,
if a radiator suitable for radiating CP of either
hand were fed with equal signals leading to both
RHCP and LHCP simultaneously, I agree with the
poster above that complete cancelation would result,
and there would be no radiation.
This is why a linearly-polarized antenna could not
receive any energy. (har har)

One of my assumptions is that the RHCP and LHCP can operate in
complete isolation of each other. DBS satellites (for example) use
RHCP and LHCP to double their bandwidth, just like FSS satellites use
H and V. I have not heard anything about the DBS RHCP transponder
having to worry about the LHCP transponder. I haven't heard any
mention of nulls suddenly appearing and disappearing in the downlink
passband as the two senses happen to coincide, out of phase. I haven't
heard about the CP being converted to linear and causing interference
(at -3dB) in the other CP mode.

I assume that the two CP signals have no knowledge of each other. The
hardware can be designed (easily) to maintain that isolation - imagine
the two transmitter hidden from each other and the signals just happen
to be headed in the same direction. In other words - for purposes of
argument - it doesn't have to be the same antenna.

It just so happens that, for this 'dual-CP' concept, the two CP
signals happen to be the same but one is inverted. They don't have to
'know' about their evil mirror-image twin.

If they cancel out, then where does the energy go? Make it a mega-watt
each and follow the smoke. If they combine in the vacuum of space,
where is the smoke?

Appreciate your comments...

de VE1BLL