Re: [Amps] 10dB and propagation

[David Kirkby <david.kirkby@onetel.net>]

K3BU@aol.com wrote:

> I have noticed this effect and I was glad to see more "proof" in 
> Rich's post.
>
> See my old propagation article at
> http://members.aol.com/ve3bmv/bmvpropagation.htm
> where I speculated (observable phenomena) that we are propagating signals 
> more as refraction/ducting rather than pure reflections from the ionosphere. 

I looked at your 1980 article:

"Electromagnetic Wave Propagation by Conduction - An innovative Theory 
Based on Fibre Optic Analogy"

You make some rather bold statements in that - e.g. 

"The present radio wave propagation theory is based on the assumption 
that radio waves are propagated by
reflections from a mirror-like ionosphere, returning to the earth's 
surface, bouncing off it back to
the ionosphere and so on."

Yet refraction of radio waves was understood well before 1980 when you 
wrote that. A Quick look at 'Cornell University's School of Electrical 
Engineering Publications'

http://rmc.library.cornell.edu/EAD/htmldocs/RMA03333.html

describes several about radio wave refraction in the 1950's, and perhaps if I looked I could find them well before that - I'm no historian. The idea of refraction was hardly new. 


Am I missing something? 

You then say "When light exits the fiber and there are some impurities, it disperses the light at various angles. It is very
difficult to enter the fiber under those conditions" 


There are such things as multi-mode fibres. Even if there were no impurities, these are known to propagate at certain angles - modes. 
A quick look at 
http://www.ciscopress.com/articles/article.asp?p=170740
says:

"By June of 1972, Robert Maurer, Donald Keck, and Peter Schultz
invented multimode germanium-doped fiber with a loss of 4 dB per kilometer and
much greater strength than titanium-doped fiber"

I'm not convinced multi-mode fibers were not known well before 1972 - I 
suspect they were. But multi-mode fibres propagate multiple modes 
without any need for impurities.

Take a bit of glass or transparent plastic rod and you will have a 
multi-mode fibre that will propagate at various angles. It has a 
cladding index of 1 (air) and a core index of whatever the glass/plastic 
you use is. Shine light down it and you will see it is contained to the 
glass. There will be a limit to the angles it will propagate, which (to 
a first approximation) you can compute using Snell's Law and total 
internal reflection.



> In 
> that case it would make a difference how signal gets into the duct. At some 
> threshold it might not make it, at some other it does. That jump in power levels 
> can be seen as not linear or corresponding to power levels at the transmitter. 
Non-linear effects can be seen in many materials, but generally need 
high field strengths - not the sort of E or H field you could produce on 
the iosphere with a transmitter on earth. At least that is my 
"gut-feeling" - I may be wrong.

--
Dr. David Kirkby, 
G8WRB

Please check out http://www.g8wrb.org/ 
of if you live in Essex http://www.southminster-branch-line.org.uk/



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