BIll (AA7XT),
There's some (but not much) measured data at HF of arriving elevation
angles (for example, Wilkins et al, Epstein et al, Utlaut et al,
Wilkins again et al, and Hallborg et al).
But I've never seen any measurements at MF. The only paper that comes
close (at least that I'm aware of) is by LaBelle. He measured arriving
polarization from 50 KHz to 5 MHz.
The only thing I can add are results of doing ray traces of the
ordinary wave (the extraordinary wave is heavily attenuated on 1.8
MHz) with electron-neutral collisions and the magnetic field included.
There appears to be three ranges of angles for propagation on
160-Meters at night. Low angles (roughly 0 to 15 degrees) give E hops.
Medium angles (roughly 15 to 20 degrees) can give ducting. Higher
angles (roughly above 20 degrees) give F hops. Whether ducting on
160-Meters occurs likely depends on the factors tied to the magnetic
field.
For a picture of these ray trace results, go to http://k9la.us. Click
on the "160m" link on the left, and look at the "ray tracing on 160m"
file at the top.
As for E hops, it's tough for most of us to put lots of energy at very
low elevation angles - but guys like VE1ZZ with take-offs over salt
water may be able to take advantage of these very low angles.
Carl K9LA
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|