[CQ-Contest] Is HF HF propagation reciprocal?

[Zack Widup]

I actually started doing my Ph.D. project on this very topic at the U. of 
Illinois in radio science in 1977.  Unfortunately, after about a year I 
decided not to pursue it further.

I do know it's most pronounced around the grayline times, for various 
reasons.

There has been some further research done on it.  K8GU is doing research 
in the same area.  I'll see if he has any directions toward further info. 
(Are you on this reflector, Ethan?)

73, Zack W9SZ

On Mon, 4 Jun 2007, Bill Turner wrote:

> ORIGINAL MESSAGE:
>
> On Mon, 4 Jun 2007 19:46:24 -0700, "Tomas Hood (NW7US)"
> <nw7us at hfradio.org> wrote:
>
>>
>> I'm working on posting additional texts where I take various HF
>> propagation topics, and use modern software to model the concepts.
>
> ------------ REPLY FOLLOWS ------------
>
> IMO, modeling software is only useful when all parameters are known.
> That is not the case for so-called one way skip. Your software focuses
> on the signal to noise ratio, which is fine, but only part of the
> issue.
>
> for years, it has been theorized that one way skip is caused by a tilt
> of the ionosphere, so that signals going in one direction strike it at
> a very shallow angle, whereas signals coming the other way strike it
> at a more acute angle. Due to the angle of incidence vs MUF, one
> signal will be reflected and the other will not.
>
> I don't know if this has ever been convincingly proven or not, but it
> sounds reasonable. Does anyone have any further information?
>
> Bill W6WRT
>