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I have read the article in the post above and agree with it. The EH antenna is the classical discone that goes back to at least 1940.
Antenna radiation is composed of two basic parts. One is that the total radiated power can never be more than the input power. The other is that in order to have gain you have to radiate power in some angles and not others. This is done by having different phases at different points. If the antenna is small compared to a wavelength you will get no gain. The inventors claim that there is a circulating current. This cannot exist because it would radiate power and ther is no input power driving a circulating current.
The theory of the discone is described in the famous antenna book by Kraus which should be available in libraries. It starts with a dipole made from cones of infinite length having constant input impedance over an infinite frequency range. The lengths are cut off to a convenient length and the impedance is constant over a large but fininte range. From here the development goes two directions. One is to flatten the cones in one dimension to produce the sheet metal bow tie antenna. The other direction is to replace one half with an infinite conducting plane. From here the infinite plane is made finite.
When the earth is used as the plane the cone is above it with the point down. When the antenna is elevated it is mechanically more convenient to have the plane on top.
**broken link removed** will give you some details on how to construct one and the attached program will do a design for you.
In general you approximate a solid sheet of metal with many wires. The angel of the cone controlls the impedance and the size (length) controls the lowest frequency. You feed the antenna where the cone and the disk come together. The outer conductor of the coax goes to one and the inner to the other. You select which by whichever is closest to where the coax comes in gets the outer.
Ham operators are building a different kind of antenna allso called EH antenna. For 27MHz I found good enough instructions for building it on site:
**broken link removed**
You can find a lot of sites describing circuitry and tunning of such antennas.
This other antenna site is an April Fool site. Note how they do not give any explanantion that can be used for construction, "apply metal, wind coils".
Their technical details are all false. The radiation resistance of a short antenna goes down with the square of the fraction of the wavelength. This is why HF antennas on motor vehicles are such poor radiators.
I haven't read site thorowly. On basis of other sites dealing with such a projects there must be a lot of missleaded people among Amateur Radio people.
It is not that they are intentionally dishonest, it is that they have a limited knowledge of physics and come up with what is consistent to their knowledge but not with the physical world. If you dig into the history of science you get the same thing with the top people in the past. Maxwell's equations were condemned by the top physicists of the day.
The problem with many hams is the false god of SWR. They do not realize that loss makes for low return loss. You might have noticed that the antenna you gave the link to was measured for SWR and not for field strength.
I am reminded of the old story of the fellow looling for his lost wallet by the street light and not where he lost it because the street light was where he could see things better.
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