Hi James, I left a word out, and I have now added the word into my below text (I added the word horizontal).
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 horizontal 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 1:30 PM Don Kirk <[email protected]> wrote: > 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 <[email protected]> wrote: > >> Don't dismiss the possibility of multipath reflections. >> >> Jim - KR9U >> >> >> >> >> -----Original Message----- >> From: Topband [mailto:[email protected]] >> On >> Behalf Of Don Kirk >> Sent: Thursday, June 3, 2021 9:10 AM >> To: topband <[email protected]> >> 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 >> >> _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
