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

And how about the tripole CP receive antenna:

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00115102

How does the helix antenna achieve broad spectrum?  Is the (apparent) 
rotational speed constant, therefore a fixed radians per change in z axis 
for any wavelength?  Or is it wavelength/frequency dependant also?

A 1982 IEEE paper for analog about a late '70s installation of a CP 
transmitting antenna:

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=01456745

Did CP transmissions for UHF ever catch on, or are they still mostly H 
polarized?  If CP is common, I would think CP antennas would be 
commonplace. 

The article states that the power requirement doubles to power each 
polarized plane for the same ERP.  Any changes there?

Dan

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Date: Wed, 01 Jul 2009 00:53:37 -0400
From: Cliff Benham <flyback1@xxxxxxxxxxx>
Subject: [opendtv] Re: VHF Stations Seek Solutions for Reception Problems, 
by D

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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