More comments.
Radio Arcala – My only experience with them is in CQ WW CW a couple years ago.
There was another OH up that a way running a vertically polarized antenna (I
don't remember at the moment if it was a vertical or a 4-Square). This other OH
had a stronger signal than Radio Arcala for the several times I checked. Note
that this is not an extensive comparison. As a side comment, when Radio Arcala
announced this project, I expressed my concern to them – but by then it was too
late. Regardless of the results, we're going to learn something (as GM3POI
pointed out).
HFTA – Those 1.8 MHz elevation angles likely came from IONCAP/VOACAP as the
program does give results below 2 MHz. The real issue is there is very little
(if any) validation data on 160m.
Elevation angles on 160m – I believe useful elevation angles on 160m fall into
three categories. With the nighttime E region critical frequency around 0.35 to
0.5 MHz, elevation angles below about 10 degrees are refracted by the E region
(in other words, E hops). The importance of these extremely low angle E hops is
not well understood. Higher angles can result in ducting at night as long as
the electron density valley above the E region peak is well formed. My guess
for these angles (from ray tracing work with Proplab Pro) is something like 10
to 20 degrees. Above 20 degrees, the wave passes through the E region and is
not refracted enough to get into the duct – so we get F hops. Please realize
this is a very general summary, as “stuff” happens.
160m differences – When considering propagation on any band, one has to
consider refraction, absorption, and polarization. With refraction by a given
electron density profile inversely proportional to the square of the frequency,
160m is bent the most and results in shorter hops. Due to 160m being close to
the electron gyro-frequency (one of N0AX's favorite words), absorption is more
than on our HF bands. This results in shorter hops with more loss. In fact, the
extraordinary wave (one of two characteristic waves that propagate thru the
ionosphere) is usually considered out of the picture on 160m due to
significantly more absorption than the ordinary wave. And again due to 160m
being close to the electron gyro-frequency, polarization tends towards highly
elliptical as compared to circular polarization on our HF bands. And vertical
polarization couples the most energy into the ordinary wave at the high
latitudes.
Carl K9LA
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Topband reflector - topband@contesting.com
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