Topband: nonlinear attenuation along signal path

[Wolf Ostwald]

Hi reflectees !

Another frustrating experience led me towards some more thinking about why
some signal seem to take a deep dive on the "last mile" and become
inaudible.

There are three major examples from EU. That is FK,FW and ZL7  . all are
some ten thousand miles away and we have numerous experiences when these
stations were copied in eastern EU and not a beep in western EU. The last
FW-DXped is another good example. It is not possible that a signal
travelling 10.000 miles becomes inaudible after 10.250 miles. Given linear
absorption along the path of course. As field strength would follow the
inverse law of the square in a linear environment. I am suspecting, that at
the "sundown"-end of the path the D and E-layers did not have enuff time to
disintegrate and therefore the last miles suffer from more attenuation than
miles in darkness further east. I have no idea of how long the absorptive
layers take to vanish. It sure leads to the frustrating effect to hear
stations a two hundred miles east, work the far away DX and having not the
faintest trace of it further west. It sure would be nice to get an estimate
of how more ERP needs to be launched to make up for the extra attenuation at
the western end of the path, future DXpeds may profit from that for sure !
Any geophysicists around with an answer ?

73 de wolf   df2py