Re: 1/4 wave TC (fwd)

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Date: Fri, 27 Jul 2007 04:07:47 -0400
From: Dave Pierson <davep@xxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 1/4 wave TC (fwd)

>> Unpowered, the resonant frequency of the secondary with no top load is
>>  about the same as the 1/4 wave frequency of the wire length in the secondary.

>>My intention with this coil was to build a secondary that would resonate
>>at the 1/4 wave frequency of the wire length used in the
>>secondary. Indeed, with no top load, the overall excited resonant
>>frequency of the secondary is only slightly below the non powered
>>resonant frequency

>Have you considered the following:
>
>1) You have made a coil whose resonant frequency has a quarter wavelength
>that is equal to the straight wire quarter wavelength, but as soon as you put
>the first bend in the wire, the "EM distance" between the two ends is no longer
> that of the straight wire. Once you have put ~380 bends in it such that the
>straight-line distance in three dimensions from end to end is  only ~19
>inches, then that quarter wave number really seems to lose any  significance.
>
>2) As the streamers form, they drop the resonant frequency of the  secondary.
>The streamers themselves become a constantly growing and shrinking  topload,
>as they form, grow, disappear, and new ones re-grow. When there is no  other
>topload, the percentage by which the streamers affect the  frequency is
>greater. Since, when anything is happening, the frequency  is constantly changing,
>what is the relevance of the wavelength at which nothing  is happening?

Good points, i believe.
Consulting the usual antenna design books, for the related case of the
'continuosly loaded' anttenna, turns up the following:
for 'long skinny' coils, the observed resonance shows a roughly
1/2 wave lengths of wire, once wound, looking like a 1/4 wave.

for 'short fat' 'coils' a 1/4 wave of wire more or less looks like
a 1/4 wave.

Each of thse will be modified (lowered....) by presenc eof a top load.

best
dwp

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