Hi James,
Yes, multipath is certainly a variable, and I'm actually trying to include
something that's not outwardly obvious regarding the directional response
of a receive antenna related to polarization versus vertical polarization
which is something I had never before considered (I'm not trying to exclude
anything), and I don't recall it being discussed before. I suspect the
signal is changing polarity frequently (probably rapidly) and probably
often appears like circular polarization, etc. so it's a very complex
picture.
Thanks,
Don (wd8dsb)
On Thu, Jun 3, 2021 at 12:57 PM James Wolf <jbwolf@comcast.net> wrote:
> Don't dismiss the possibility of multipath reflections.
>
> Jim - KR9U
>
>
>
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces+jbwolf=comcast.net@contesting.com]
> On
> Behalf Of Don Kirk
> Sent: Thursday, June 3, 2021 9:10 AM
> To: topband <topband@contesting.com>
> Subject: Topband: Interesting observation and comment (Skewed Path Vs.
> Horizontal/Vertical Polarization)
>
> While playing around with my portable flag that I designed for MF/HF radio
> direction finding, I noticed something that confused me for about a year,
> and I finally figured out what's going on which led me to think about the
> 160 meter skewed path comments I've seen over the years and wonder if some
> of the observed phenomena is really Vertical versus Horizontal polarization
> of the received signal and not really a skewed path.
>
> There is a local 10 meter beacon that uses an attic dipole and my portable
> flag as well as my tuned and untuned direction finding loops always
> indicate
> the signal is located approximately 350 degrees from my QTH
> whereas I know this is not correct. The beacon WA4OTD is actually located
> 8.6 miles away at a heading of 267 degrees (I'm almost 90 degrees off from
> the correct herading).
>
> Then a few weeks ago I noticed that when my good friend Jay (W9TC) was
> operating on 20 meters that my portable flag did not point in the correct
> direction of his house, and he's located 2.8 miles from my QTH and he uses
> horizontal beams on 20 meters. I then orientated my portable flag so it
> was
> horizontal versus the normal vertical orientation that I use, and "bingo"
> the portable flag now indicated the correct direction. I then went back
> and
> obtained a heading on the WA4OTD beacon on 10 meters with the portable flag
> orientated horizontal, and now it points the correct direction (mystery
> solved).
>
> I then went and looked at various antenna models using 4NEC2 in which I
> looked at the vertical gain versus horizontal gain of the antennas when
> mounted in their normal orientation, and this explained what I was seeing.
> Small loop antennas mounted vertical have a maximum horizontal gain that's
> shifted 90 degrees from the maximum vertical gain direction. I then
> modeled
> beverage antennas and their maximum horizontal gain is shifted 45 degrees
> from their maximum vertical gain direction.
>
> I suspect the polarization of received signals on 160 meters is constantly
> changing, but wonder if the skewed path observations over the years
> indicates the polarization of the received signal has shifted to
> predominantly horizontal versus vertical or a mix of both? Maybe a crazy
> thought, but thought I should share my observations with the topband group.
>
> I've not really had a problem tracking down typical local noise sources on
> MF/HF using my portable DF antennas orientated for vertical polarization,
> and that confirms the many comments that local noise on MF/HF are typically
> propagated vertically, but thought my observation was very interesting and
> it unlocked a year long mystery about the local signals that were
> intentionally transmitted using horizontal polarization that did not track
> well with DF gear that normally does a phenomenal job.
>
> P.S. it took me a while to figure out how to look at vertical gain versus
> horizontal gain using 4NEC2, but it was sure worth the effort. Normally
> 4NEC2 displays total gain.
>
> Just FYI, and can't wait for the comments to come flooding in about my
> crazy
> idea :) 73, Don (wd8dsb) _________________ Searchable Archives:
> http://www.contesting.com/_topband - Topband Reflector
>
>
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