It seems to me that ducting between the E and F-layers would
provide an explanation for the "searchlight" effect observed recently.
The landfall of the searchlight would relate to finding stations with
appropriate launch angles such that the RF could enter or exit the duct.
Too low an angle and you'd never get in! This would only occur for
certain relationships of solar flux (read "critical frequency") and launch
angle.
In times of higher flux, when the E-layer reflection is nearly total, a
low launch angle would be desireable to minimize the number of hops. With
minimum flux, the launch angle would again need to be low to minimize
hops, but this time off the F-layer. At intermediate conditions, such as
being experienced now, the higher launch angle would provide a greater
chance of entering the duct.
Because so many of the Big Guns have efficient, low-angle radiators, the
searchlight effect will be much more pronounced. Us Little Pistols with
broader vertical lobes will be less affected. But only until things quiet
back down ;-)
Not a stringent analysis, but seems to fit the picture.
See you in the Stew.
73, Ward N0AX
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|