[Prev][Next][Index][Thread]

Re: Self Capacitance formulas

Hi Will,

	I should have been more specific. Kraus was certainly not the first
to use a helix as an antenna. But before him everyone was trying to use the
helix in the NORMAL mode, which as we know and Tesla probably knew, is not
an efficient radiator of power. However, it pretty certain that Kraus WAS
the fisrt to recognize that if you pump a helix with much higher 
frequencies that it becomes a very directional and efficent radiator. In
fact, it shares many attrributes with a phased-array antenna.  The 
multiple peaks and nodes on the helix act like a bunch of little antennas
which are in phase in certain directions in space (along the axis) and are 
out of phase in all other directions. Another cool thing about the axial 
mode (Kraus) is that the radiation tends to be circularly polarized --
this can never happen in a normal mode helix which acts more like a simple 
1/4 wave antenna with linear polarization(they have very similar 
radiation resistances too).

	Kraus does deserve a lot of credit for having the intuition to 
guess that a helix might have other interesting modes besides the NORMAL 
mode.

-Ed HArris