Yuri, Kk3BU wrote:
"But when signals are going throug the ionosphere and considerable
distances, things don`t jive exactly like that."

Yuri is nost likely correct. Even line-of-sight paths experience strange
things.

Isotropic material has the same characteristics along any axis. Kraus
left himself an out by saying:
"It is assumed that the emfs are of the same frequency, and the medium
is linear, passive, and also isotropic." I think he implies that
reciprocity may not rule when the medium is as screwed up as it often is
in the ionosphere.

I had one nonreciprocal microwave path among a countless total in my
experience. It connected a rooftop in downtown Houston with the
company`s aircraft hanger at Houston International (now Bush) Airport.
The path ran from the company headquarters northward right up the street
in a canyon between skyscrapers, several of which had more than our 33
floors. The signal at the airport was stronger than that at headquarters
by several dB. As we had more than 40 dB fade margin in both directions,
I scratched my head but lost no sleep.

I have HF radio experience between Germany and Portugal while working in
shortwave broadcasting. We used HF for an order-wire between locations.
Signal strengths and path losses seemed to be nearly identical in both
directions. Transmitters were 3.5 KW Collins Auto-Tune all-purpose
AM/CW/MCW with a rotary phone dial to select mode and frequency.
Receivers were Hammerlund SP 600Xs.

Best regards, Richard Harrison, KB5WZI