Jim Lux wrote:
>>the professionals have
>>known about this for generations, and now we have those tools on our
>>desktops. Most of the work has already been done for us in the HFTA
>>program and its propagation data files.
>
[...]
>Providing you have a horizontally polarized antenna (but many amateurs
>DO have horizontally polarized antennas, so that's ok).
>
Extending HFTA to vertical polarization has to be top of everybody's
wish list... but the whole problem is much more affected by ground
conductivity and permittivity a long way out from our antennas. To do it
accurately to be worthwhile, it might require more information than we
can ever know.
>VOACAP is also free, and a wonderful program to fool with.
>
It certainly shows that wave angles are a game of statistics, varying on
several different timescales at once: hour to hour, day to day, month to
month and year to year around the solar cycle.
The Handbook shows wave angle statistics averaged across a complete
solar cycle, but I'm sure there's more to be gained by running VOACAP
oneself and digging into the detail.
>There's been some fascinating work from Chris Coleman in Australia on
>using propagation models and lightning maps to work out the spatial
>distribution of atmospheric noise, which is almost as important in
>antenna pattern design as where the desired signal is coming from. In
>fact, on the receive side, where the antenna isn't sensitive is
>probably more important than where it is.
>
That's a well known effect on 6m, where vertical stacking distance can
have a big effect on the total noise power received from very high
angles that have no value for communication:
http://www.ifwtech.co.uk/g3sek/stacking/stacking2.htm#50mhz
--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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