At 12:58 AM 12/9/2005, Ian White GM3SEK wrote:
>Jim Lux wrote:
> >
> >
>
>If Bob (who started this thread) buys the ARRL Antenna Handbook to get a
>copy of HFTA, he'll find that author N6BV approaches the whole problem
>in a radically different way.
>
>Instead of jumping straight into antenna engineering, N6BV is much more
>strategic about it.
>
>1. Which band? Where do you want to work to? So, what takeoff angle do
>you NEED?
>
><snip>
>What we've been neglecting is that terrain, antenna height and your
>strategic goals (the parts of the world you want to be "big into") are
>all EVEN MORE important.
>
>The idea of engineering the whole antenna system to meet the needs of
>propagation is a relatively new one for amateurs. Until recently we
>didn't have the tools for propagation and terrain analysis, so we have
>tended to downplay how important they are. But 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).
VOACAP is also free, and a wonderful program to fool with.
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.
Jim, W6RMK
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