[TowerTalk] polarization change

[Jim Walker]

Then would the optimum antenna be one that would be a directional (with F/B
and side rejection as well as gain) antenna that rotates on the horizontal
plane i.e. a typical yagi beam); that could also be tilted along the axis of
the boom....from a  horizontal to vertical position.

I guess one could also design a quad fed for both horizontal and vertical
polarization with the ability to switch between the two polars.

  

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Michael Ryan
Sent: Friday, April 10, 2009 12:22 PM
To: 'jim Jarvis'; towertalk at contesting.com
Subject: Re: [TowerTalk] polarization change

All comments have been very interesting, but I think Steve may have already
nailed this thing with the comment about having MULTIPLE antennas to choose
from. One may hear better ( or transmit ) than the other at any given time
due to variables.  It pays to have choices.  This may or may not be possible
for some.  '73 all. Enjoy the Easter Weekend. - Mike

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of jim Jarvis
Sent: Friday, April 10, 2009 11:08 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] polarization change


I wasn't going to comment on this, because wiser heads have prevailed, on
this topic, for the most part.

HOWEVER,  I learned something today that may be worth contributing to the
discussion:

I have always assumed that fading was principally a result of changes in
arrival angle, due to ionospheric dynamics, and accepted the literature
which said that all signals arrived
horizontally polarized.   This morning, I learned that it may be  
polarization that is the principal
variable.

At k2ttt's place, getting my taxes done, we were playing with his new K3,
and discussing the
impact of having dual receivers.   This past season, on 160m, he had  
an inverted vee,  horizontally
polarized, and a loop, which was fed to be vertically polarized.

By putting one antenna into each receiver, he was able to observe that the
principal variable
seemed to be polarization.   Selecting diversity receive, he had dead  
solid signals, when either of
the individual channels was fading to the point of no copy.

Although 160 may be different from higher bands, this anecdote does seem to
run counter to the prevailing wisdom that the ionosphere tends to make all
signals arrive horizontally polarized.

While this strictly speaking belongs on the topband reflector,  one antenna
was hung from a tower,
and the other had to avoid coupling to the tower.   So the comment is  
peripherally relevant to TT.

N2EA




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