christofire wrote:
"Art Unwin" wrote in message
...
The majority of antennas used today are (commercial) circularly polarized


That probably isn't true for VHF/UHF. Take a look at the website of a major
supplier of professional antennas such as
http://www.amphenol-jaybeam.com/base...nas-search.php. Entering
CP in their search engine for base-station antennas yielded 2 results wheras
entering VP yielded 365!

One of the reasons for greater use of linear polarisations in professional
applications is frequency re-use on the orthogonal polarisation some
distance away - i.e. the value of the limited VHF/UHF spectrum. That's
certainly true in Europe.


Ham antennas remain in the linear domain (ala the Yagi and similar)
There are many reasons espoused in CP advantages in "point to point"
What is the main advantage hams hold over the more popular circular
polarized antennas in its "skip" type useage versus "point to point" ?


Extensive use is made of 'mixed polarisation' for transmitting VHF FM
broadcast services in Europe. It may not be pure circular but it contains
significant vertically- and horizontally-polarised components. The mobile
and portable receiving antennas have whatever polarisation they end up with,
more or less by accident, and fixed rooftop antennas are usually linearly
polarised. DAB and terrestrial television are transmitted using V or H
linear polarisation.

Chris


Off subject I know but as a matter of interest what happens to a TX CP
antenna with a clockwise twist transmitting to a RX CP antenna with an
anticlockwise twist, over short to medium vhf/uhf paths, I would have
thought a reduction in signal ?

Pedr GW6YMS