Message-ID: <001c01c294ca$75536720$205d063e@main>
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: "LF-Group" <rsgb_lf_group@blacksheep.org>
Date: Mon, 25 Nov 2002 21:30:01 -0000
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Subject: LF: HBG de W1TAG
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Hi John, your plot continues to be interesting. The little (well 10dB !!)
peak at 1500z looks like it roughly corresponds to the time when the sun is
due south (i.e. radiation strongest) at the mid point of the path. To my
thinking this indicates that there is perhaps a one-hop mode operating. We
have sometimes seen this when there has been daytime transmission of CFH due
to geomagnetic storms. I believe that DCF39 which is stronger than CFH shows
this effect often......certainly John VE1ZJ mentioned it several times.

I think , although I have not checked it on geoclock, that the dip at 0915z
this "morning" might correspond to the dawn at the mid-path point (at 90kms
altitude, rather than at sea level) I have not normally seen a deep dip on
East<>West paths so I am not sure about that one. It will be interesting to
see if it occurs every "morning". I believe it could be the sun illuminating
the D-layer from underneath (as described in a Bob Brown paper in QEX ) and
building up a thick absorbing layer. As later the sun's altitude increases,
it pushes up the electron density still further but from above and forces
the "reflection level" down reducing the thickness of the absorbing layer
that the waves must tranverse.  Don't take this a gospel.....I am just
trying to make sense of it in my own way.......and waiting for someone to
say  "that is rubbish because....".  You sometimes have to stick your neck
out to get a good discussion going !!

Cheers de Alan G3NYK
alan.melia@btinternet.com