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

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.

That is correct and is the FCC standard.
Good post Bert,
Dale

-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx
[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Manfredi, Albert E
Sent: Tuesday, June 30, 2009 1:37 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


----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org

- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.

 
 
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at 
FreeLists.org 

- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: