Message-ID: <001d01c1a978$cb5fafe0$a537073e@default>
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: "LF-Group" <rsgb_lf_group@blacksheep.org>
Subject: LF: Propagation
Date: Wed, 30 Jan 2002 10:10:24 -0000
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Hi Rich, I am afraid that in my opinion the propagation conditions on 160m
and LF are completely different. There may be some features that are the
same but (and I may be wrong here) I believe that long distance 160m is
mainly propagated by F layer reflection whereas LF does not penetrate the
E-layer. Most LF propagation seems to be by 'reflection' from the bottom of
the E-layer (at night) or from the lower regions of enhanced ionisation in
the D-layer (daytime).

Since early December, there has been evident in Brian's (CT1DRP) plots of
DCF39 that there has been enhanced daytime signals (6 to 10dB above the
average for early September ), and depressed night-time signals. These have
been confirmed by occasional plots of CFH from my location, when It has
appeared. The usual cause of the conditions described has been ions injected
into to D-layer by the big geomagnetic storms. The after-effects of the
storm can last up to 20 days, before, I presume, these energetic ions decay.
The strange situation at present is that there has been little geomagnetic
activity since late November to early December and yet the conditions at
night has stayed depressed. There is a sign this morning that things are
getting back to normal as I logged a carrier on 137,010 or there abouts
which I assume is CFH. The overnight levels were better than they have been
recently but there is still a lot of deep fading. These condition usually
indicate the end of a propagation even and a return to 'normal' conditions.
The fact that the carrier is still strong here at 1000z suggests that we are
not fully clear of the ions that give enhanced day-time conditions yet. This
enhacement of ionisation in the D-layer would also give increased absorption
of 160m signals, but I guess the Hawaii station was talking about night-time
paths.

Cheers de Alan G3NYK
alan.melia@btinternet.com