The measurements by the Wheeler Cap method, the accepted efficiency test for
small antennas, show greater than 90 per cent for the 13 inch high cone,
using 12 inch slant height, and 16 inch diameter at wide end, with four
folded quarter wave parallel lines (folded monopoles) wound around the cone.
This compares to high 90's for a full size half wave dipole. This was on a
ten meter model.
Because of the interaction of the four folded monopoles, each must be made
between 20 to 30 per cent longer than half a dipole to get in band resonant
point you want. It is suggested you wind on one cut longer than formula for
half a dipole, (234 over f Mhz), and see what its frequency is, and adjust
and wind others by the percentage you are off where you want to be.
The ten meter prototype easily worked East Coast stations with 25 watt rig,
on an average propagation day, from the open garage door of a lab in Central
Tx. Most testing has been on antenna range with spectrum analyzers, s
parameter testing and so forth to date. Same size models down to 8 MHz have
been made, and a ten meter model only 6 inches high using smaller wires have
been tested.
73, Stuart K5KVH
73,
Stuart K5KVH
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