Topband: one- way propagation

[Robin]

 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 at sasktel.net>
To: "'Robert Briggs'" <vk3zl at bigpond.com>; <topband at 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..
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