Alex, I believe that the problem occuring here is that many are using words
like refraction, reflection
as being interchangeable. I see a mountainside when operating close to as a
reflector though
it may well be an absorber too. Anything, both behind or in front of a
driven element is a diffractor, thus its length alone
with respect to the driver does not determine whether it reflects or not.
If one solely focusses on the typical yagi
then it is easy to talk in general terms which are not applicable to other
arrays which leads to erroneous
descriptions. It is quite easy to design an array where there are many
elements behind the driven element and many
would be of lengths both shorter and longer than the driven element but
because they are closely coupled they can represent a single, longer element
as coupled elements introduces quanlities other than simple physical
length..
Regards
Art

"AB2RC" wrote in message
...
On 2005-02-16, Buck wrote:

We know the ionosphere affects propagation. It is assumed that
signals take the same path and therefore should have the same
strength, but I don't think so. If the ionosphere is dense (relative
to my frequency) behind and over my station, I may be using it as a
'dish' reflector. However, at your location, you may have a porous
ionosphere so rather than your signal being reflected, it is being
absorbed. The result is that I have an ERP of 200 watts and you reply
to me with an ERP of 20.

takeoff angle also plays a big part in this. One station may have a lower
angle and be making only 1 hop to the other station, while the other
station
may have a higher angle and be hitting the first station via 2 hops --
resulting in some signal loss.

--
Alex / AB2RC
Linux is user friendly, however it is not idiot friendly