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Re: Flat coils & undamped waves (was Wire Length)

Original poster: "Gav D" <gdingley@xxxxxxxxx>

Hi Ed,
I am probably splitting hairs here, but is it more likely that the
inductance of a cylindrical coil is greater than a spiral employing
the same amount of copper, rather than Q; the ac resistance perhaps
remaining the same?

Also I think I am right in saying that a spiral coil provides less
magnetic coupling, and so in the case of TCs this provides a better
condition for free resonance (i.e. less quenching required on the
static gap)?


On 1/17/07, Tesla list <tesla@xxxxxxxxxx> wrote:
Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Why is flat coil geometry significant in this or any other context?  Is
there any electrical or functional difference between using a flat
secondary and a helical secondary, beyond one being much more difficult
to fabricate?

Perhaps I'm not understanding something correctly, but my understanding
of an "undamped wave" is just a waveform that stays at a constant
amplitude, as is the voltage coming out of an AC socket, an RF
transmitter, or CW oscillator.  A "damped wave" is what you get in a
disruptive Tesla coil, where the amplitude begins at some peak value and
diminishes exponentially with time.  Aren't all of these references to
undamped waves just referring to the output of a very high frequency
mechanical CW alternator - a high frequency variant of what powers our
power grid?

Vacuum tube Tesla coils and some non-disruptive solid-state coils do
generate CW, or undamped waves, but Tesla lacked the technology to do
this using active devices.  Did he couple a mechanical high frequency
alternator into a matching resonant transformer, to boost the voltage
and produce a true CW Tesla coil?  Was resonant-rise involved?  While in
theory he had the technology to do this and could have built a CW coil,
the only coil topology he used that I'm familiar with is with disruptive
spark gap technology.  I can't figure out just what he was doing from
the text you cited.  Perhaps vagueness was his intent?

Gary Lau

 > Original poster: "Gary Peterson" <g.peterson@xxxxxxxxxxxx>
 > Ed, Bill, and Mike,
 > It's good to know we are all in agreement that Tesla's 1898
 > flat-spiral type transmitter is, in fact, a spread spectrum Tesla
 > coil RF transmitter.  The unanswered questions are 1) is the
 > transmitted energy spread out in the intervening portion of the RF
 > spectrum between the upper and lower frequencies, and, if so, how
 > much of the transmitters RF energy appears in this region?  2) If
 > there is RF energy in the intervening portion of the band, does this
 > energy contribute to the operation of the wave complex receiver?
 > As for my comment about Tesla being able to "generate practically
 > undamped waves," I was giving him benefit of the doubt in regards to
 > one of his methods, which had been used, and still is, for creating
 > damped waves.  A search for "undamped" in "NIKOLA TESLA ON HIS WORK
 > WITH ALTERNATING CURRENTS and Their Application to Wireless
 > Telegraphy, Telephony and Transmission of Power : An Extended
 > Interview" produces results directly related to the 1898 flat-spiral
 > transmitter.  For example,
 >      "In the meantime, as I was developing all this, I had
 > already struck a new line of effort toward producing vibra-
 > tions; namely, I had developed a system permitting me
 > to take the ordinary current of any main and transform it
 > into any kind of vibrations I desired, either damped or
 > undamped." [p. 11]

<massive snip (please see original post Subj: Re: Wire Length)>