From: WarmSpgs@aol.com
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Date: Fri, 6 Aug 1999 12:34:24 EDT
Subject: Re: LF: eclipse
To: rsgb_lf_group@blacksheep.org
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If it may be any help in knowing what to expect from the eclipse, I can 
summarize some of the effects of the 1995 total solar eclipse over North 
America.

That one entered the US from Mexico over western Texas, tracked through 
Oklahoma, over southeast Kansas, through Missouri, then on up across the 
northern Midwest.  Given that I live in the southeastern US, this put the 
path of totality about 450 km to my northwest.  Extending that same line 
beyond the ground track another 450 km (give or take), one finds Fort 
Collins, Colorado, the home of time station WWV at five convenient spots in 
the HF bands, plus WWVB at 60 kHz.

Hence, totality fell dead-center between my QTH and a stable source of 
signals at several frequencies of interest.  I entered each of those in my 
receiver's memory, along with one of the (formerly) clear-channel MW 
broadcasters from Dallas, a few shortwave broadcasters (whose paths didn't 
cross the eclipse track) for reference, the CHU shortwave time signals from 
Canada (on the opposite side of the eclipse, but at a later time), and a few 
aeronautical beacons from the central states in the 200 - 400 kHz range that 
I can normally pick up at night.

I found that I could scan all of these, logging S-meter indications and any 
audible effects, in less than three minutes.  (This proved to be the source 
of considerable writer's cramp once the actual loggings were underway.  If I 
ever do this again, I will dictate into a tape recorder.)  I decided to 
perform the scans on a five-minute cycle during the main event, which would 
allow me to return to any frequencies of particular interest twice or more 
during that time on a case-by-case basis.  I began logging at 10-minute 
intervals from roughly two hours before totality reached the midpoint of the 
WWV/WWVB propagation path, to two hours after, switching to five minute 
intervals as soon as it appeared anything was happening.

And indeed it did happen!  The 2500 kHz and 5, 10, 15, and 20 Mhz WWV signals 
went through an approximation of sunset, night, sunrise, and daytime signal 
levels again, all in the space of just over half an hour.  The relative 
strengths of 15 and 20 Mhz were different for an extended period after the 
eclipse, although not having had another eclipse with which to repeat the 
experiment makes it impossible to say whether there's any significance to the 
observation.  Later, the CHU time signals underwent a similar night and day 
reversal.

On MW, there was distinct audible enhancement of the Dallas station, but it 
didn't move the S-meter into a useful part of the scale.  The LW aerobeacons 
were even less productive.  None of the reference shortwave broadcasters' 
signals appeared to be affected.

However, 60 kHz yielded quite dramatic results.  Well before and well after 
the eclipse, the WWVB signal was at its normal daytime level here, marginally 
above noise.  Almost 40 minutes before center-path totality, though, it faded 
out entirely!  It later returned, rising to nighttime levels (over 10 db 
above daytime levels) when totality was over the center of the propagation 
path.  After totality, it again faded to oblivion for a time, finally 
returning to daytime levels.  This seems to parallel the fade we normally 
experience from WWVB here at sunrise and sunset.

My guess would be that the longest, most profound effects will be seen below 
about 100 kHz.  Above that frequency, effects do occur where the eclipse 
track crosses the propagation path; but the higher one goes in frequency, the 
less change I'd expect to see in signals not directly crossing the track.

We'll see how it turns out in practice.  Good luck to all.

73,
John  KD4IDY