Topband: Long Path

[John Kaufmann]

W4ZV wrote:

> The most interesting
> aspect of "long path" is the consistency of signal azimuths at ~210 degrees
> before local sunrise and at ~150 degrees after local sunset.  This fact is
> independent of true azimuths and is most likely influenced by the location
> of the terminator which closely aligns with these two directions at sunrise
> and sunset.  

Although I tend to agree with most of Bill's comments, there are some
notable exceptions to the coincidence of LP and skewed LP propagation with
the greyline. From New England we occasionally get skewed LP propagation on
160 to VK6 at our
sunset in Dec. and Jan.  Both VK6VZ and VK6HD come through on this path.
However, the heading is 45 to 90 degrees, which is neither a true LP nor a 
greyline path along the terminator (both of which would be around ~150
degrees). 
I have also heard JA's at this same heading at our sunset in winter, although 
true LP propagation to JA (on the rare occasions it occurs) via the ~150 degree 
path is more prevalent. 

LP propagation to W1 is much more common on 80 than 160, of course.  Here, I 
have observed many instances of LP and skewed LP.  Southeast Asia is worked on 
the ~150 degree heading around local sunset.  In winter this corresponds to the 
greyline.  However, this path persists into our spring season at the same ~150 
degree heading whereas the sunset greyline has shifted to the southwest.  In 
other words, the 150 degree heading still works but is no longer a greyline 
path.  This past spring I worked 9M2AX on 80 (beaming SE) at his sunrise (my 
sunset) on a regular basis until early May, at which point there was too much 
daylight on my end for propagation to hold up any more.  This is clearly a 
skewed path of some kind since short path to 9M2 is in the NNE direction from 
W1.

There is something going on to produce these instances of non-greyline skewed 
paths, although I'll leave it to others to explain what it is!
 
73, John
W1FV

P.S.  John I agree about the VK6 path...there is a similar path at Western
NA sunrise to the Indian Ocean area...FR5, 3B8, 3B9, etc.  I think these are 
exceptions because their true azimuths are closer to due East/West than
North/South and a different mechanism may be at work...de W4ZV.


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