Bill,
In my experience, "one-way propagation" is primarily a result
of large differences in the noise and interference environments
on each end of a propagation path. This is a very common
phenomenon when one end of a 160, 80 or 40 meter path is in
full daylight and the other end is in full darkenss.
On the daylight end of a 160, 80 and 40 meter path, the D layer
significantly attenuates atmospheric noise and adjacent
frequencies are not typically occupied by strong signals. On the
full darkness end of the path, atmospheric noise is significantly
elevated and nearby frequencies are often occupied by very
strong signals.
73!
Frank
W3LPL
---- Original message ----
>Date: Mon, 3 Oct 2005 07:09:22 -0500
>From: "Bill Jackson" <k9rz@radiks.net>
>Subject: [TowerTalk] K7C - One-Way Propagation?
>To: <towertalk@contesting.com>
>
>Towertalk Gang,
>
>Here is an excerpt from one of the recent K7C dx'pedition
bulletins, regarding poor signal quality they appear to be
experiencing on their end:
>
>"Let's start with a technical consideration of which you should
be aware. As you already know, we are using vertically-
polarized antennas very, very close to salt water and with large
radial fields. This makes our signal launch angle very, very low -
quite a bit lower than most horizontally-polarized antennas on
dry land. As a result, the K7C signal has been reported to be
very loud on the receiving end. This doesn't mean, however,
that you are just as loud here. All it takes is a couple of
extra "hops" from a higher launch angle and your signal will
change from an easy-to-work S5 to being undetectable. The
K7C team has observed a number of occasions when it is
obvious that you can hear K7C easily, but on our end the pileup
is only an unworkable S-1 grumble. This is most pronounced at
the beginning and end of an opening so you may be hearing us
long before or after we can hear you. Marginal openings on the
paths to Europe, the Middle East and Northern Africa may be enti
> rely "one-way" - incredibly frustrating for you to have K7C be
as clear as bell, but not hearing the most important DXer of all -
you."
>
>Does this explanation make sense? I would think that an
antenna with a high angle of radiation on transmit would also
favor signals with high arriving angles on receive. The amount
of signal attenuation on a signal arriving at a low angle at the
station with the antenna transmitting with a high angle of
radiation should be equally diminished. Therefore the station
with the horizontal antenna over dry land should have trouble
hearing hearing K7C as well.
>
>What am I missing here?
>
>Even though I have managed to work them on both 80 and
40m, they have never had what I would call a LOUD signal,
compared to what I often hear from KH6 land.
>
>73 de Bill
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