[opendtv] Re: VHF Stations Seek Solutions for Reception Problems, by D
- From: dan.grimes@xxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 1 Jul 2009 11:57:34 -0700
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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