an added note/comment here
During the XZ0A expedition, I think we conclusively proved that:
1: Skew paths exist and are repeatable
2: the arrival angle of the signals is NOT reciprocal.
The arrival angle of the XZ0A signal as heard in the eastern/central US was reasonably
normal, and extended into sunrise in the way we have generally come to expect, Direct
angle measurements were, of course, not made, and are unlikely to be measurable except by
inference.
The arrival angle of the signals from NA as heard at XZ0A were clearly and repeatedly very
high. Beverage antennas did NOT hear the signals, whereas a very low dipole heard the
signals fine, and repeatedly, night after night.
the point is that if we received exclusively on the beverages, we would have an apparent
difference in signal strength of at least 15 dB - the apparent level of the signal
arriving at XZ0A would be 15 dB less than the XZ0A signal as measured in NA, with
comparable transmit ERP. TX was 2KW into a full size elevated radials quarter wave (a 200
ft tower with an insulator a quarter wave down from the top)
this TX level is comparable to many higher performance stations in NA and significantly
less ERP than some stations with large TX arrays,
The noise floor was definitely an issue, us being in the middle of Asia, BUT, when there
is 20 dB difference between the signal heard on ANY beverage, and the signal heard on a
full size dipole at 10 ft, its pretty conclusive that the pattern of the antennas was a
serious effect. The relative noise level heard on the dipole was still quite a lot higher
than we would have liked- the Asia noise propagates at high angles as well as low ones,
but was comparable to the beverage noise floor, less some directive effects
the point is, the path is NOT symmetrical. A number of complex explanations have been put
forth, and I'm waiting for occams razor to slice down to the meat.
Robin Critchell, WA6CDR
(XZ0A XZ1N VP6DX)
----- Original Message -----
From: "Doug Renwick" <ve5ra@sasktel.net>
To: "'Robert Briggs'" <vk3zl@bigpond.com>; <topband@contesting.com>
Sent: Tuesday, December 04, 2012 17:14
Subject: Re: Topband: one- way propagation
Nope, Nope. I am a firm believer in one-way propagation on 160m, having
witnessed it many times. Let me give you a recent example. In the last
weekends contest I worked LY7M. We both run decent stations. We exchanged
emails after including actual signal strength. Saulius copied me 579; I
copied him 539 with my 4-square. When I called he came right back to me.
QRN, QRM, QSB were not a factor at my end. Often I will hear a weak EU
station calling CQ will little response. I call and I am copied
immediately. Anecdotal you say. True but many times experience trumps
theory.
Doug
-----Original Message-----
Interesting theories and observations regarding one way propagation..My
take is that most of the seemingly one way prop is more dependent on
operator skill and the local qrn at one end of the circuit..With the
current conditions this past 12 months most usually strong signals on
the band are often attenuated due to less than a reliable path..I hear
many signals that may be only S1-3and few hear a station calling
them..These conditions may give the impression of "one way" prop but it
is more likely due to qrn conditions at the listening end...I am looking
at this from the VK cross the Equator Summer/Winter differences which
have a big influence on making a contact..My observations over 35 years
show that there is propagation most of the time all year if stations
take the time and patience to listen for DX..
Bob..VK3ZL..
_______________________________________________
Topband reflector - topband@contesting.com
_______________________________________________
Topband reflector - topband@contesting.com
_______________________________________________
Topband reflector - topband@contesting.com
|