[Elecraft] EH Antenna Patent

[John, KI6WX]

Tony
>
> But seriously. I don't think anyone has ever claimed EH has more gain than
a
> regular dipole. I believe the claims I've seen in print, is that a good
EH,
> mounted at the correct height *approaches* the gain of a well-erected
dipole
> whilst having a very small size compared with a full-size dipole.
>
> This is a very important point, because how many people can erect a full
> size 80M or 160M dipole in their backyard? Even a full size EH antenna for
> 136KHz can be built by obsessives in larger backyards. Personally I think
it
> is a waste of time to compare a 20M EH with a good 20M dipole. Moe
> importantly, lets compare a 160M EH with a compromise 160M dipole. That
> would be a more significant test.

This really is an impedance matching issue.  A wide impedance range antenna
tuner can match a physically short antenna, or a non-resonant antenna.  The
E-H antenna patent describes a matching network to broadband match a
physically short antenna, but you will be limited to one band.  A KAT2
antenna tuner might do just as well with the same antenna, but you could use
the antenna on many bands.  The key to the gain relative to a full size
dipole is the loss in the matching network and I see nothing in the patented
matching network that would be lower loss than other possible matching
networks.
>
> There are two other claims in the patent which I think are very important
to
> test. Firstly on RX the antenna is supposed to be deaf to E-only radiation
> and H-only radiation. Therefore the ant is supposed to have good immunity
to
> man-made electrical interference. Some testers have reported that fact.

For far field noise, the E and H field strength are always related by the
impedance of space.  For near field noise, the E and H fields may differ
from this, but the power in these components always fall off faster than
distance-squared, so they don't propagate very far.  Polarization
discrimination is important; most local noise is transmitted by power lines
which preferrentially transmit a horizontal E-field; a vertical E-field
antenna will respond less to this noise.  Finally, your transmission line
and its connection into your radio can also have a large effect on noise
sensitivity; the mismatch at the antenna can effect this sensitivity.
>
> The second claim is that by use of some kind of "dish" behind the antenna,
> it will be possible to "focus", or at least sheild from directions other
> than the intended path, the outgoing and incoming radiation. Again the
> focussing/shielding of radiation in this way very problematic in most
> backyards, particularly on 40, 80 and 160M. The implications of this type
of
> working are enourmous - including the possibility of EME HF transmission &
> reception.
>
This won't work because of diffraction.  The reflector would have to be a
significant fraction of a wavelength to have any effect.  You would be
better off using several of these compact antennas in a phased array to
provide gain in a specific direction.  Just because a patent makes a claim,
doesn't mean it will actually work.  My favorite patent illustrating this
principle is 6,025,810 "Hyper-light-speed Antenna".  This is for an antenna
that transmits a signal faster than the speed of light.

-John
 KI6WX