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

  • From: "Hunold, Ken" <KRH@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 30 Jun 2009 16:57:05 -0400

Paraphrasing Doug Lung:

 FCC rule Section 73.682(a)(14) require that CP or EP antennas be
right-hand polarized.



It could still be a coin toss at the receiver, determined by whether
your strongest signal (or echo) has had an even or odd number of
bounces.

Ken Hunold



-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Manfredi, Albert E
Sent: Tuesday, June 30, 2009 4:37 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: VHF Stations Seek Solutions for Reception
Problems, by Doug Lung

Dale Kelly wrote:

> If one uses a standard H pol receive antenna for the comparison 
> testing, assuming equal signal intensities, CP and H-Pol results will 
> seem to be identical (in a generally free space environment).
> However, if one uses a CP receive antenna, the reception from CP is 
> superior. Also, such testing should include marginal antennas and 
> orientations and a multipath environment (where DTV CP should be 
> superior with modern DTV receivers.)

Is there a standard for CP transmissions, i.e. clockwise or
counterclockwise (e.g. when viewed from the transmitting end)? If not,
then results using a CP receive antennna would be a coin toss.

The difference between an antenna that is both H and V polarized, and
one that is circularly polarized, is the 90 degree delay line between
the H and the V in the CP antenna. So then the question is, which
polarization gets the 90 degree delay? If H is delayed wrt V, the effect
is clockwise from the transmitter.

The other aspect is power. Seems to me that CP antennas are a bit like
full-wave rectifiers. There are more peaks of E field per unti time
being transmitted out there to the ether, as it were. So the more ideal
H or V polarized receivers will actually not do as well, since they
won't get the benefit of all of the transmitted power.

Bert
 
 
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