> But more importantly, 100 km is too
> low to provide much help to us
> Topbanders. This is far below the E
> and F layers of the ionosphere that
> we rely on for DX.
The peak of the nighttime E region is around 110 km, so 100 km is not too far
below the E region. The lower E region is also where most absorption at night
occurs on 160m.
More to the point, refraction is inversely proportional to the square of the
frequency. An electromagnetic wave at 1.8 MHz bends more and doesn't get as
high into the ionosphere as our HF (3-30 MHz) energy.
At night, with the E region critical frequency around 0.4 MHz, energy at
elevation angles lower than about 5 degrees is refracted back to Earth by the E
region.
Thus the E region may be more important than we normally think.
Carl K9LA
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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