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Offline rabinoz

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Re: Line of sight communication
« Reply #100 on: June 20, 2016, 02:40:19 AM »
Quote from: Tom Bishop
Again, some ranges are more transparent to the atmosphere than others.

Evidence?

I looked at a very distant mountain in broad daylight and it was somewhat dark and muddied.

Is this a haiku or something?  We are talking about transparency to various radio transmission frequencies. Please get back to us will relevant evidence.

Inb4light=radio

Its a proof of the statement that some ranges of photons are affected by atmospheric opacity.
Oh come on! You are claiming that some microwave links are limited to around 50 km distance and others can cover 360 km due to the differences in "atmospheric opacity" to essentially the same frequency ranges.
Please tell me how the design engineers manage to design these links on the basis of the globe radius.
They even get the expected wave interference (multipath transmission) if the main lobe of the beam gets too close to the ocean waves!

This is getting just too fanciful and removed from the real world!

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Offline Tom Bishop

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Re: Line of sight communication
« Reply #101 on: June 20, 2016, 02:46:49 AM »
Where is your evidence that it exactly matches the globe radius?
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

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Offline Rama Set

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Re: Line of sight communication
« Reply #102 on: June 20, 2016, 04:21:16 AM »
Quote from: Tom Bishop
Again, some ranges are more transparent to the atmosphere than others.

Evidence?

I looked at a very distant mountain in broad daylight and it was somewhat dark and muddied.

Is this a haiku or something?  We are talking about transparency to various radio transmission frequencies. Please get back to us will relevant evidence.

Inb4light=radio

Its a proof of the statement that some ranges of photons are affected by atmospheric opacity.

It does nothing for your claim though.  Your claim is very specific, and so your evidence, in order to be relevant, has to be specific to the radio frequencies we are discussing.  It is well know that different frequencies of light interact differently and your anecdote, not even evidence, is irrelevant.
You don't get races of anything ... accept people.

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Offline rabinoz

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Re: Line of sight communication
« Reply #103 on: June 20, 2016, 04:25:28 AM »
Where is your evidence that it exactly matches the globe radius?
I did not say "exactly matches the globe radius" and in fact it probably does not "exactly match the globe radius"! Whatever you say or fuss about quite variable refraction is a fact of life in microwave link design, celestial navigation, surveying and astronomical observations near the horizon.

You could take a look at Basic Principles for understanding atmospheric refraction phenomena.
Quote
atmospheric refraction
Introduction
Green flashes, mirages, astronomical refraction, dip of the horizon: these are all related phenomena. But there are some basic ideas that are helpful in understanding all of them. The purpose of this page is to point these out. (A more technical page is also available.)
Overview
One principle is to realize how all these pieces fit together:
Astronomical refraction is all the atmospheric refraction between the observer and some point outside the atmosphere.
Green Flashes are caused by the dispersion of astronomical refraction.
Terrestrial refraction is just the part between the observer and some object inside the atmosphere.
Mirages are extreme examples of terrestrial refraction that sometimes occur for objects that are (usually) beyond the horizon.
Dip involves just the refraction between the observer and the apparent horizon (usually, the sea horizon).

Designers of these links commonly make a rough allowance for "typical" refraction by using an effective earth's radius of (4/3) x raduis, but the actual refraction very near the horizon if rarely near its "typical value".
 
I said that the do their designs of the basis of the globe radius, and basically the links work and they also find that if the beam width is too wide the main lobe will get too close the the waves (for a sea crossing) and cause multipath transmission problems.

I have, I believe, given copious references to these designs in the past and don't intend wasting my time with your nit-picking now!