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Re: radio propagation



This is a distinct example of the danger of appealing to authority, I suspect.
An amateur could do worse than consult the ARRL Handbook which offers this:

"An ionospheric layer is a region of considerable depth, but for practical
purposes it is convenient to think of it as having finite height.
A simple reflection from the layer would give the same effects as those
resulting from the gradual bending that actually takes place."
[there follows some discussion of variable frequency ionosondes, and their
range sensing...]

On the other hand, this is not a Feynman talking about his mythical
100% efficient screw jack.

Brian



At 11:16 4/17/01 -0400, you wrote:

Go to Feynman, Vol II, 7-3 "Plasma oscillations".
The discussion is short and not mathematically taxing - I'll tease you with
part of the concluding remarks:

"[So]if one tries to propagate a radiowave through the ionosphere ... it can
penetrate only if its frequency is higher than the plasma frequency.
Otherwise the signal is reflected back . . ."

Bob Sciamanda
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: Ben Crowell
To: PHYS-L@lists.nau.edu
Sent: Monday, April 16, 2001 11:31 PM
Subject: radio propagation


I was looking through some of my father's ham radio books
recently, and came across something I didn't understand.
They describe how radio signals (we're talking
about 20-40 meters typically) propagate over long
distances by multiple reflections from the ground
and the ionosphere.


brian whatcott <inet@intellisys.net> Altus OK
Eureka!