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Old 23rd Dec 2010, 1:48 pm   #1
Skywave
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Question Ionosphere layers: names?

As we all know, the propagation of radio waves makes extensive use of the ionosphere for reflection & refraction: the D, E, and F (F1 and F2) layers.

Hence, my questions: why does the so-called D-layer have the 'D' suffix? Did it simply acquire this letter on account of its daytime properties? (The E and F logically following, of course). And what happened to the letters A, B and C? Were these originally assigned for the three types of ground-wave propagation? If so, my question is thus answered.

Despite a thorough search in my extensive technical library, I could not find an answer - so I thought I'd ask here.

Just curious: I'm sure that there is an obvious answer; such questions fascinate me!

Al. [Skywave]
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Old 23rd Dec 2010, 3:00 pm   #2
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Default Re: Ionosphere layers: names?

Seems they start at A http://www.arrl.org/files/file/ETP/A...EarthAtmos.pdf
 
Old 23rd Dec 2010, 4:19 pm   #3
Skywave
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Arrow Re: Ionosphere layers: names?

Thanks.

However that data seems to relate to the physical structure (temperature and density) of the Earth's atmosphere; it doesn't appear to apply to regions of ionised layers that we refer to in radio. The data for the various heights of the named layers does not match the generally recognised heights of the D-layer for example: 60 - 80 km. approx. (Source = Radio Communications Handbook, 6th. edition, RSGB). Your source also make no reference to the F-layer.

Mind you, I was somewhat taken aback by the remark:
"Tiny particles called meteoroids travel at very high velocities & can easily penentrate the human skin"

Al.
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Old 23rd Dec 2010, 4:31 pm   #4
Skywave
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Arrow Re: Ionosphere layers: names?

Actually, there is a C-layer: reflections as low as 20 km. height:

http://www.vigyanprasar.gov.in/scientists/SKMitra.htm

Al.
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Old 23rd Dec 2010, 4:45 pm   #5
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Default Re: Ionosphere layers: names?

I think I read that during or following the work done by Heaviside, Kennelly and Appleton to determine the structure of the ionosphere in the 1920s and 1930s, someone had the presence of mind to start at D (or E - I can't remember now), just in case future research revealed lower layers, which it did.

There is indeed an ionospheric C layer, but not an A or B as far as I know...

Regards,

Ian
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Old 23rd Dec 2010, 5:43 pm   #6
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Default Re: Ionosphere layers: names?

Quote:
someone had the presence of mind to start at D
Bloomin' brilliant.
 
Old 23rd Dec 2010, 5:59 pm   #7
Skywave
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Thumbs up Re: Ionosphere layers: names?

"Brilliant" - agreed!

It's interesting to speculate as to the choice of the 4th. letter of the alphabet: it's almost suggestive that there was some suspicion that there may well have been 'active layers' closer to the Earth - but perhaps not that many, i.e. three.

Seems to me then that this choice was simply another classic example of the insightfulness & cautiousness of the thoroughly-trained scientific mind: "we're not altogether sure about this at the moment, so we are going to give ourselves a little breathing space".

Al.
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Old 23rd Dec 2010, 6:37 pm   #8
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Default Re: Ionosphere layers: names?

I went to Polytechnic so long ago they actually taught us something about RF!

The telecoms lecturer, Brian Shaw (who later turned out to be a fellow amateur enthusiast too), gave us this way of remembering the layers:-

D amn good attenuator
E rratic
F airly (or another F) good reflector

Merry Christmas

73 Fred
A65BD
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Old 24th Dec 2010, 1:11 pm   #9
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Default Re: Ionosphere layers: names?

When I worked at Chelmsford Marconi, on the roof of Marconi House a large radio dish was built and that was a Tropospheric Scatterer, this being the lowest layer. Now sadly Marconi New Street is derelict with just feral graphiti spray on the historic buildings, due to inept security and uncaring council who's job it should be to stop the place being vandalised.
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