Topband: GAP Vertical Question

[Ashton Lee]

What I can add from personal experience is that a vertical dipole (center fed half wave) without radials, on a rocky cliff top is an absolute killer antenna on the upper HF bands. My vertical dipole works so well that in contests I often just quit using my yagis because of the hassle of rotating or even switching them. The omnidirectional vertical is only maybe 3 dB down on very good directional antennas.

Center fed half waves on 160 are a lot harder to set up, so I have no experience there. But if I had a used broadcast tower it sure would be fun to try one.




On Dec 17, 2012, at 7:33 AM, "Carl" <km1h at jeremy.mv.com> wrote:

> 
> ----- 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 
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