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William Howard wrote:
> It is disappointing that Tesla is used a basis for so many
> conspiracy theories and related pseudo science.
Not so much these days, there's lots of up to date reliable
info out there now to balance things out. This mailing list
is firmly moderated which helps a great deal.
The '1/4 wave myth' that others mention refers to an obsolete
notion that the length of wire wound into the secondary
continues to resonate at the frequency it used to do when it
was a straight length of wire.
For example, take 1000 metres of wire. In a straight line
its 1/4 wave frequency would be 300e6/(4 * 1000) = 75kHz.
Wind that wire into a coil with length/diameter ratio of say,
4:1, and the 1/4 wave resonance rises to around 120kHz, no
longer 75kHz.
A variation on the myth recognises that the frequency rises
when you turn the wire into a coil, but goes on to suggest
that you should then add enough topload C to pull the resonance
back down to equal the original frequency of the straight wire.
However nothing special happens when you do that, although
it does lead to a large topload which is usually good for a
classic TC. Perhaps that explains the persistence of the myth.
> Secondary and primary work best when they are the same length
> or a at least 80% of the secondary length.
A helical primary 80% of the secondary length is unusual
I think. Might be wrong here but 10% or 20% could be more
typical. Where did the 'spot heating issues' occur that led
you to such a long primary?
--
Paul Nicholson
--
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