Re: Helical Antennas (was Self Capacitance formulas)

>>From will-at-eletex.elec.ryukoku.ac.jp Fri Jan 12 20:20 MST 1996
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<tesla-at-grendel.objinc-dot-com>; Fri, 12 Jan 1996 16:58:43 -0700
>Date: Sat, 13 Jan 96 08:56:57 JST
>From: William Reiken <will-at-eletex.elec.ryukoku.ac.jp>
>To: tesla-at-grendel.objinc-dot-com
>Subject: Re: Self Capacitance formulas
>	Ok this is good news.  I seem to be on the right track.  Just lucky
>I guess.  However, for the best reference on Antennas and esp. Helical Antennas
>you should read the Antenna Bible;
>	Antennas
>	John D. Kraus
>	2nd Ed.
>	McGraw-Hill
>	ISBN:  0-07-100482-3
>	Dr. Kraus was the inventor of the Helical Antenna.  I don't know much
>about this subject since I am just starting out here.  However, I guess a
>bible is a bible?
>							Will...
Hello Tesla fans,
        Your are correct that Kraus was one of the pioneers in helical
antenna theory.  Helical antennas can operate in a "normal mode" or an
"axial mode", depending on the operating frequency (wavelength).  Tesla
coils operate in "normal mode" as helical antennas.  "Normal mode" is a very
inefficient method for operating a helical antenna.  As a result, tesla
coils are quite inefficient at radiating RF energy, especially if the
wavelength is long (where tesla coils are normally operated).  Helical
antennas work best in "axial mode", which occurs when the operating
wavelength is comparable to the length of a single turn of the coil.  This
occurs at very high frequencies and is quite useful for space
communications, etc.  Kraus's text provides a nice explanation, but most of
the text concerns axial mode operation, which is of interest to antenna purists.
Mark S. Rzeszotarski, Ph.D.