[BC] Directional Antenna Proofs

[James B. Potter]

" The thing is, tree roots and the like can break the wires. How many of
yours are still intact?"

All of them are.  

The 5-tower array is a parallelogram with an odd tower thrown-in for night
pattern; is situated on a 15 acre grass field which is mowed by a nearby
farmer for hay production. It's flat as a pancake with no other vegetation.
The surrounding area is a semi-rural community having undergone little
improvement/growth over the past 20 years; mostly agriculture, dairy, and
horse farms.  Ozark, 7 miles to the north on US 65 and Branson 26 miles to
the south have expanded over the years; but there are no major new nearby
industrial, commercial, or residential developments of any consequence
constituted since the array was first planted in that field.  The earth is
hard around the towers and there is no evidence of any destruction of
radials.  The area surrounding each tower is fenced and covered with plastic
mulch topped with white pea gravel -- no weeds.  Except for fading paint on
the towers, the place looks almost like it did in the original pictures 2
decades ago.  The white paint on the cinderblock tower buildings and
transmitter shack is peeling, but that's about the extent of the evidence of
ageing.  Big hairy spiders and a few rats and snakes here and there feeding
on each-other.  

Right now it's hot and dry -- worst case for MW propagation.  The soil
conductivity is horrible, but probably no different from the day the array
was commissioned: it's rock just beneath the surface; can't put a spade down
into it.  

There is one minor clue, but I don't know what to do with it.  Tower #4 is
our reference tower, and the only one that is top-loaded using the guy
wires.  For some reason, we can't get an impedance reading with our in-line
bridge; but we can on the other 4 towers.  But the base current, current
ratio and phase are what they are spec'd to be.  If that tower really was
out of the range of the impedance bridge, I would expect real trouble with
the current and phasor, but not the case.  It remains a mystery. 

Thanks for everyone's very helpful comments and literature references.

Regards/J