[EIDXA] more sunrise chat

[David J. Schmocker]

This stuff is just too fascinating to pass up.  (see below).
Incidentally, if any of you get to meet K9LA (from Indiana) either at 
Dayton or at the W9DXCC convention in Chicago in Sept (each year), 
Carl's a very intelligent propagation source.  He's a great conversation 
if you want to discuss propagation ideas/traits.

I don't know him personally, but have talked with him briefly at 
W9DXCC..and I've seen a number of articles he's written on the subject 
of propagation..

73 enjoy

(are my BS7H distractions working)?  My strategy is to keep all of you 
studying sunrise until after I've worked BS7H and then you can join in 
the pile-ups..   ... are we having fun yet?

Dave KJ9I


-------- Original Message --------
Subject: 	Re: Topband: sunrise
Date: 	Sun, 22 Apr 2007 09:52:03 -0400
From: 	Carl K9LA <k9la at gte.net>
To: 	topband <topband at contesting.com>



There appears to be two issues with sunrise and propagation on the low 
bands.

First, the signal enhancement around sunrise that W7LR mentioned is 
believed to be due to tilts in the E and F regions at sunrise, bringing 
signals out of the duct in the electron density valley above the E 
region peak in the nighttime ionosphere. See Nick VE7DXR's feature in 
the July/August 2001 QEX, which includes plots of medium frequency 
enhancements and a side-view look at the ionosphere around sunrise.

Second, the D region ultimately limits daytime propagation on the low 
bands (to roughly 1500km on 160m CW for good stations), which is mostly 
due to solar radiation at 121.5nm ionizing nitric oxide at D region 
altitudes. When this starts is not only dependent on when the D region 
"sees" the sun, but it also is affected by the ozone layer delaying this 
radiaton in reaching the D reigon. Bob NM7M has written several articles 
about this issue.

Carl K9LA


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