[Elecraft] E-H Antenna Simulation in NEC

[Stuart Rohre]

Tony, the FLEX antenna will probably offer you all the compactness you
desire and still decent bandwidth, (70 kHz at 7 MHz), all in a size that is
no more than 8 feet tall at 160m, and proportionately smaller at higher
bands.  Now these are one band antennas at this time, but our R&D group is
working on multiband models.   We have working models of 60 per cent
efficiency only 6 inches high for 20m.  If you go up to 14 inches high you
can get up in the 90 per cent ranges for total efficiency.  And this is the
antenna alone radiating over a ground plane 6 by 6 feet, not the feedline
radiation, as a balun is used or a cable choke.

Papers have appeared in Antennas and Propagation of IEEE USA, and in IEEE
Antennas Symposium proceedings, June 2002.

The secret is a folded unipole element, which is replicated a total of four
elements in parallel around a cone shape.  The feedpoint is the point of the
cone, the wide end has the shorted side of the quarter wave lines that make
up elements.  The angle of the cone support is typically 40 degrees.  This
for the 14 inch slant height model.

The inventor is Robert Rogers, a local K5.  Applications to date have been
for ship to ship communications and ship to shore, as well as ocean research
buoy telemetry to ship or shore.  These are all HF ground wave and sky wave
experiments, but the ground wave is much better than the typically helical
short vertical on fiberglass rod.
73, Stuart K5KVH