[TowerTalk] Monoband Yagi stacking heights

[Al Williams]

This is a timely subject for me as I plan to install them at 85' and 53'
(70' tower + 15' mast and highest overlap section of crankup).  I have never
had a yagi higher than 45' (TA33) so no experience but a lot of reading and
EZNEC modeling.

There seems to be a difference between what EZNEC and antenna books say and
what Towetalk postings most often say.  The postings usually have specific
heights in feet and desired communication destination, most often Europe and
the Caribbean/South America.  The books and EZNEC usually reference
wavelength height (frequency) and elevation angle (from which path hop
distance can be determined).

Because higher yagis have multiple elevation lobes at the higher
frequencies, I would think that the heights should be selected so as not to
duplicate the elevation angle lobes if one wants to spread the distance
path.  On the other hand, the heights should be (?) selected to duplicate
the elevation lobes if maximum gain is desired at the expense of not
spreading the distance path.

Further, I suspect that optimum antenna heights for Sweepstakes activity
from Midwest locations would be different than from coastal locations
whereas the optimum height for
worldwide paths may not be so different.

I have selected 85' and 53' not because of analysis but rather it "fits" the
70' crankup tower. I am planning to be able to switch to use U/L/B and am
hoping for a significant improvement from my previous trapped TA33 at 45'.
Comments will be appreciated

k7puc




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