Topband: Daylight QSO

[Bill Tippett]

SM6CPY:

 >I have followed the "daylight qso" discussion with some interest. Here are
a few european notions: Quite often this winter I have heard (and once
worked) UA9KAA calling CQ well after my sunrise around 7Z (8 local time).
His local time must have been around noon indicating that his waves
travelled in daylight all the way to my rcvr.

         UA9KAA is on the Arctic Circle (perpetual darkness at
this time of year) so "daylight" has little meaning.  Sweden
is also far north so the sun never reaches a high azimuth
angle even at local noon.

         I think the "daylight" discussion is getting a little
"long in the tooth", but if we really want to continue it,
I suggest we look at the actual paths using something
like DX Atlas to see whether we are really talking about
"daylight" or "twilight" with the sun at very low angles.

         Eric K3NA did some work on this in 2005:

"I think distance to the terminator is a more appropriate metric
than the oft-quoted "I worked him an hour before sunset".
Depending on time of year and latitude, a terminator that is
1500 km away could reach the station at widely different times:

     Sep 22 on the equator: 52 minutes.
     Dec 22 in London: 2 hours 28 minutes.  (The terminator is
never more than 1770 km away, even at noon.)"

http://dayton.contesting.com/archives//html/Topband/2005-11/msg00040.html

                                         73,  Bill  W4ZV