Re: LF: Effective antenna height?

[Andy Talbot <andy.g4jnt@gmail.com>]

I now see that same text is repeated on page 52 of the   LF Experimenter's Handbook, so the pages I just copied don't give any extra info .

There was no further detail to be found in either of the two earlier LF Source Books

Oh well

Andy  G4JNT

On 23 September 2017 at 11:37, Andy Talbot <andy.g4jnt@gmail.com> wrote:

I have the very book in front of me.  The LF Source Book

There is a littel bit of justification for those values, but not much.   They seem to be experimental

Photo of the two pages covering LF Verticals can be found here

http://www.g4jnt.com/DropF/lfsourcebookpg210.jpg

http://www.g4jnt.com/DropF/lfsourcebookpg211.jpg

Andy  G4JNT

On 23 September 2017 at 11:18, Mike Dennison <mike.dennison@ntlworld.com> wrote:

Knowing the effective height of a Marconi antenna is essential in the
calculation of radiated power /antenna efficiency at LF/MF. The
formula for this includes figures for the capacitance to ground of
the vertical and horizontal wires. The result being somewhere between
50% and 100% of the actual height.

As long as I have been interested in LF - over 20 years - I have seen
(and used) a figure of 5pF/m for the capacitance of the horizontal
wire and 6pF/m for the vertical wire. However, I have recently been
asked how this figure originated, and must admit that I don't
remember. Was it amateur experimentation, or a professional source
such as the Admiralty Handbook? The very first amateur UK LF book, a
slim spiral bound volume by Peter Dodd, may have the answer but I
don't have a copy. Peter's bigger follow-up book, The Low Frequency
Experiemnter's Handbook, published in 2000, already takes these
figures as understood.

Can anyone help, please?

Mike, G3XDV
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