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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