[Elecraft] dipole antenna efficiency

[Ron D'Eau Claire]

David wrote:
I'm also fairly sure that the amount of wire to wind on the helix is 
significantly different from the amount that would be used in a straight 
line.  My gut feeling is that it should be less, but I haven't 
researched that, either,

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I have experimented with continuously-loaded antennas (those with the
radiating element a long space-wound coil) and found Doug DeMaw's estimates
quite close: a half wavelength of wire space wound with spaces equal to the
wire diameter on a small diameter form will resonate against ground like a
1/4 wave linear Marconi antenna. For example, I space-wound 135 feet of #12
wire on a 2X2 inch wooden form. The antenna was about 12 feet long.  Working
against ground, it was self-resonate in the 80 meter band. So it takes
roughly twice the amount of wire that would be needed if it was stretched
out in a straight line. 

Ron AC7AC