"Robert Casey" wrote





North/South paths were excellent, but East/West paths were
non-symmetrical,
which suggests a tilted ionosphere. The further north you were, the more
exaggerated the effect was. I was hearing the W7/VE7's weak and watery,
but they reported my signal as huge. Meanwhile W1/VE1's who I had
20-over
were CQ'ing in my face.



Didn't think that could happen. I thought light (here radio waves)
would propagate equally as well going as well as coming back.
Like "If you can see my face I also can see your face".

Imagine that the ionosphere is an imperfect mirror which reflects signals
best when they arrive at some specific angle, and reflects less well when
the signals do not arrive at that optimum angle. Now imagine that the
"mirror" is tilted to favor one direction (your signals arrive at mirror at
the right angle, but mine arrive at a more oblique angle and are
consequently refracted more than reflected, and at the same time the
reflection angle is such that my signals pass "over your head" to a more
distant point. ). I will hear you well, but my signal will be attenuated.
From my end the skip appears "short", but from your end the skip will appear
"long".

Only when the mirror is equidistant between us and when it is "flat" will
the path be symmetrical and relative signal strengths reciprocal.

73, de Hans, K0HB

KØHB wrote:


Only when the mirror is equidistant between us and when it is "flat" will
the path be symmetrical and relative signal strengths reciprocal.



Somehow I would have thought that light (radio waves) could travel
either direction
on the same exact path. And that attenuation either way would be identical.
Same for the same set of multiple paths.

But it's been years since Physics class......

Robert Casey wrote

Somehow I would have thought that light (radio waves) could travel
either direction on the same exact path.

You'd think so, but 'taint so.

And if you spend any time on HF during disturbed solar condx, you will
receive many vivid demonstrations of non-reciprocal/non-symmetrical
propagation paths.

73, de Hans, K0HB
--
There is no voodoo or magic associated with RF
propagation. There are several perfectly sound
technical reasons why it is beneficial to occasionally
sacrifice a goat in your antenna field.

"Robert Casey" wrote in message
...
KØHB wrote:


Only when the mirror is equidistant between us and when it is "flat" will
the path be symmetrical and relative signal strengths reciprocal.



Somehow I would have thought that light (radio waves) could travel
either direction
on the same exact path. And that attenuation either way would be
identical.
Same for the same set of multiple paths.

But it's been years since Physics class......






The ionosphere is not like a mirror, as Hans stated. And from what I
understand the waves don't actually bounce, but they are bent back towards
earth.

Dan/W4NTI

Robert Casey wrote in message ...
KØHB wrote:

Only when the mirror is equidistant between us and when it is "flat" will
the path be symmetrical and relative signal strengths reciprocal.

Somehow I would have thought that light (radio waves) could travel
either direction
on the same exact path. And that attenuation either way would be identical.
Same for the same set of multiple paths.

But it's been years since Physics class......

As W4NTI points out, the ionosphere isn't really a reflector - it's a
refractor. The waves are bent, not bounced.

When the ionosphere is stable and uniform, it behaves *like* a mirror,
and the 2 way reciprocity thing works well. But when it's tilted,
twisted or otherwise distorted, the refraction in one direction may be
different than in the opposite direction.

As an analogy, think of "one way" mirrors in optics and how they
behave under the right conditions.

73 de Jim, N2EY

"If it happens, it must be possible"

73 de Jim, N2EY