[BC] Engineering Advice

[Peter Moncure]

Mark Humphrey wrote:
> It's probably a binomial feed.
>   
and Glen Kippel wrote:
> I see no reason to blast any power down the side of the hill (OK --
> it's 1600 feet high so you easterners would call it a "mountain") and have
> it ricochet off out of phase with the main lobe.
Binomial feeds are somewhat less efficient for the vertical aperture 
they use, but that cost is more than repaid by the elimination of 
locally induced multipath, as Glen suggests.  There is a *lot* more of 
this going on than many suspect.  I can think of several installations 
built to improve RFR toward the base of the tower for various reasons 
which ended up with a far better fringe signal, as the standard 
deviation is in many cases much reduced.  One tale involved the major 
metro B's calling the FCC to take the newly penetrating A to task, only 
to discover that they were exactly making rated ERP--it just didn't vary 
so much at distance while traveling radially away from the binomially 
fed antenna.  And when sigma is 3 dB instead of 10, that matters.  They 
can, for reasons not entirely clear to me, also exhibit less variation 
in axial ratio when side-mounted.  (anyone care to comment on that, RF?)

As always, YMMV.

</soapbox>

Best regards,

-- 
Peter Moncure, VP RadioSoft
706.754.2725 -2745 FAX
PMoncure at RadioSoft.com
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