Topband: GAP Vertical Question

[Carl]

----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <topband at contesting.com>
Sent: Monday, December 17, 2012 9:07 AM
Subject: Re: Topband: GAP Vertical Question


>> Right, typically a couple hundred ohms.  Modeling the base Z of a thick 
>> broadcast tower is very difficult with MoM software.  Changes in 
>> thickness can result in large base Z changes.
>
> Just to be clear, since the discussion drifted to half-wave radiators, my 
> comment above was specific to the modeling of thick v. thin half-wave 
> radiators, including the 180-195 degree radiators of some well-known 50KW 
> AM stations.  The results when modeling the base Z of approx. 1/4-wave 
> radiators is less affected by thickness, probably due to a lower base Z to 
> start with.
>
> Paul, W9AC

In the 1920's several BC towers were half waves without radials on hilltops. 
Performance was poor due to the height plus the lack of a decent ground on 
solid rock limiting the ground wave signal to a low value.
As a side note tapered towers were also in vogue but that presented other 
problems.

It wasnt until the educated scientific studies of the 30's and published 
papers/books that resulted that broadcasters began to standardize.....along 
with some push from the FCC.

Here we are over 70 years later still arguing the subject and embroiled in 
myths and some folks are very protective of their alternate beliefs.

Did the 100mpg carburetor ever exist? Is this planet only 9000 years old (-; 
?

Carl
KM1H