[Elecraft] E-H Antenna Simulation in NEC

[John, KI6WX]

Just for fun, I ran the E-H Antenna described in the patent 6,486,846 in
NEC-4.1.  I used the antenna and matching network described in Figure 1.
The antenna consists of two aluminum cylinders that are 12" long and 4.5" in
diameter.  The operating frequency is 7 MHz.  I assumed that the Q of the
parts in the matching network were 1000.  The calculations were done with
the antenna in free space.

The input impedance of the antenna is 0.036-j2114 ohms.  This is a very low
radiation resistance with lots of reactance that needs to be removed in the
matching network.  The efficiency of the radiating elements in the antenna
is 98.9%.  This is expected since the radiating elements have a large
diameter.

The very low resistance and high reactance are a real challenge in the
matching network.  The simulations show that the matching network will
dissipate most of the power.  Less than 1% of the power will get through the
matching network to the antenna.

Finally, the matching network does not force balanced currents to flow
through both terminals of the transmission line.  This means that the
transmission line will radiate.  I would expect that most of the radiation
will occur from the transmission line if it is longer than a few feet.  If
it is longer than a 1/4 wavelength, the overall efficiency of the antenna
and transmission line could be pretty good even though the antenna is
radiating less than 1% of the power.

-John
 KI6WX