[opendtv] Re: VHF Stations Seek Solutions for Reception Problems, by Doug Lung

Manfredi, Albert E wrote:

Thanks, Dale.

Cliff Benham wrote:


Does this also mean that a circularly polarized receive antenna is
also a *single channel* antenna as well?


Aha. I think I see what you're asking. Like, can CP antennas be used for
transmitting MIMO-like signals. Sounds like no is the answer. For that,
you want the maximum possible isolation between the polarities. Here,
ideally, they would be identical and just phase-shifted.


No.
I was asking about a circularly polarized antenna being used only for receiving TV signals.
If a circularly polarized antenna has a 90 degree phase delay between the H&V elements 
then it follows that it is only good for one frequency.
This is because the 90 degree delay line is only 90 degrees at one particular frequency.
At a lower frequency it would be less than 90 degrees. At a higher frequency it would be more than 90 degrees
Therefore a circularly polarized TV antenna used for receiving is only a "single channel" antenna.

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