I think this is a wording issue. We all understand the difference between VF in
the transmission line and VF in free space.
What caused difficulty was the term "arriving at". I took this to mean "at the
antenna" not free space, as there's no need to mention the antenna if the
desired meaning was "free space".
Chuck
> From: w8ji@w8ji.com
> To: charlesh3@msn.com; donovanf@starpower.net; topband@contesting.com
> Subject: Re: Topband: BOG question
> Date: Thu, 1 Oct 2015 18:57:09 -0400
>
> > I believe there is a large influence of height above ground on VF.
> > From a theoretical basis, this has been "known" since Wise's classic paper
> > "Propagation Of High Frequency Currents In Ground Return Circuits" (1934).
> > This was experimentally verified in the Litva and Rook report from the CRC
> > (Canada), and compared with theoretical results.
> > These guys didn't extend their calculations to right-on-the-ground
> > antennas. The attached (if it gets through the server) is from a
> > spreadsheet of mine based on the Wise equations. The influence of height
> > on VF is very very pronounced.
> > Chuck
>
> Frank is absolutely correct in what he said.
>
> The velocity factor decrease in the Beverage has nothing to do with the
> arriving wave velocity that affects the required phasing spacing. The wire
> looks longer because the earth slows the wave ***in the wire's transmission
> line mode***. The required spacing and stagger is set by the wave, not the
> wire. It is the same in a BOG, a normal Beverage, or in a vertical.
>
> The broadside spacing, to increase directivity a useful amount, has to be up
> around 1/2 wave or more. The end-fire or echelon spacing has to be the same
> as a normal Beverage, or vertical, to have useful directivity increase.
>
> The only thing the earth does is slow the velocity in the transmission line
> formed by the wire and earth image. The antenna cannot be a long as a
> regular Beverage because of the slowed propagation in that "transmission
> line". It is little different than loading the wire with any lossy
> dielectric.
>
> While the antenna is limited to less length because of velocity factor in
> the wire's transmission line mode, the fact it is a BOG has no bearing on
> the wave velocity, or the required spacing or stagger.
>
> 73 Tom
>
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