Allodoxaphobia wrote:
On Tue, 12 Jun 2007 11:50:24 -0700, Jim Lux wrote:

Alfred Lorona wrote:

Is there a site that explores/explains the latest theories on one way
propagation? The ARRL antenna book is not much help on the subject.

One way propagation is possible if there is an anisotropic medium in
between (like the ionosphere).

A polarized wave may get rotated in passing through the ionized medium,
then refracted differently depending on the polarization. If you
envision your launching a beam up to the ionosphere, the place on the
ground that it hits after "reflecting" would be different depending on
the polarization. If someone in the "reflected spot" sent a beam back
to you, it too would get rotated on the way, and might propagate to a
spot other than yours.


Then _that_ would explain why I've seen "one way propagation" more
decidedly on 6M versus 15M or the such. I'd think reflections and
rotations would be more 'intense' at 50 Mcs., than at lower HF freqs.

I've had distant 6M ops give me 'honest' 5/9+10, 5/9+15, 5/9+20 reports
when I could only honestly give them S-4, S-5, S-6 reports. Doesn't
happen often, but I've experienced it.

Very much so..

The assumption of reciprocal paths goes completely out the window when
you have polarization and anisotropic media.

Another example of nonreciprocal paths (albeit not for electromagnetic
waves) is sound travelling some distance where there is a wind shear.
The propagation velocity varies, so sound travelling "with the wind"
tends to bend down, while "against the wind" tends to bend up. Same
thing occurs, very strikingly, with temperature gradients.

I would imagine that conditions conducive to tropospheric ducting would
have similar effects, but I can't think of a non-reciprocal example off
the top of my head.

73
Jonesy