[TowerTalk] 15 meter yagi height for 6000 miles

[Jim Lux]

On 3/3/12 12:59 AM, Steve Hunt wrote:


  sometimes it might be more important to avoid a null falling
> at an elevation where there is a significant chance of signals arriving,
> than to squeeze the last fraction of a dB out of the long-term Figure of
> Merit!
>

YES..
Especially since the angle of arrival statistics don't say anything 
about the strength of the signals.  Just because you have a high 
probability of signals arriving doesn't mean they are weak, and you want 
maximum gain there..

But if you have a NULL where signals are coming in, that's what you 
don't want.

Another factor to consider is where the noise comes from.  If you're 
looking at working Oceania from California at local early afternoon in 
the summer (not that this is a good idea.. it's an example), there's 
thunderstorms generating noise behind you in the midwest.  Suppressing 
the noise from behind (particularly if you have something like a dipole) 
might be a better way to choose the height than the forward path.

The whole topic of optimizing antenna patterns for expected propagation 
and desired links is a fascinating and non-trivial problem.  It's why 
programs like IONCAP (and its children) were written.