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Author Topic: Clarification on grayline propagation...  (Read 326 times)
KT5MR
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Posts: 34




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« on: Yesterday at 07:38:43 AM »

Hi all,

If I am understanding the grayline properly, it is the area around the Earth's terminator in which the E and F layers are still relatively highly ionized by the sun, but the D layer is not; basically twilight.

I've learned that propagation is not always nice and neat, but is working a station with grayline propagation generally require both stations to be in twilight, or can one station be in twilight and the other in the range of full sunlight or darkness?

The reason I am asking is that last night I was on JT65 on 20 meters.  A station in French Polynesia popped up and I, unsuccessfully unfortunately, tried to work them.  They faded out rather quickly after 3 am UTC (10 pm local).  JT65 records all signals it hears, so I looked back and noticed that I first started hearing them around 2 am UTC (9 pm local).  During this hour, the station started out weak, became strong, then went weak again and finally faded out completely.

I happened to look at a day/night map and noticed that during this brief window in which I could hear them, French Polynesia was in twilight. 

So I'm unclear....to what extent was my hearing the station due to grayline propagation?  Do both stations have to be in twilight, or does only one need to be in twilight like my French Polynesian station while I was in full darkness?

--Michael / KT5MR

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N3QE
Member

Posts: 3932




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« Reply #1 on: Yesterday at 03:18:36 PM »

Some tell me that "true grayline", requires both ends to be in twilight.

That said there can be a real enhancement for many paths, even those not really on the low bands, when just one end or the other is in twilight.
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KB8GAE
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Posts: 151




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« Reply #2 on: Today at 08:41:26 AM »

Michael,

This link corresponds to what I have experienced.

http://www.ng3k.com/Misc/n4kgprop.html

Hope it helps.

73's Rich KB8GAE
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