Re: 1/4 lamda and intial sec design parameters (fwd)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: Tesla List Moderator <mod1-at-poodle.pupman-dot-com>
 >
 > ---------- Forwarded message ----------
 > Date: Fri, 16 Jul 2004 23:10:56 -0600
 > From: Gerry Reynolds <gerryreynolds-at-earthlink-dot-net>
 > To: Tesla list <tesla-at-pupman-dot-com>
 > Subject: Re: 1/4 lamda and intial sec design parameters
 >
 > Hi Ed,
 >
 > In view of previous posts, could you define your 1/4 lamda point?  Also, the
 > "minor" resonances you refer to, are these harmonics of the fundamental or
 > other spurious frequencies?  If not harmonic, then could you describe the
 > spurious mode (maybe an example)?
 >
 > Gerry R
 >
 > > Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 > >
 > > "Using a large top load capacitance, ie 2-4 x the dia. of the sec coil,
 > > helps
 > > force the best resonant point near the 1/4 lamda point.  Also, the large
 > > top
 > > load, sphere or toroid, reduces considerably the values of the minor
 > > resonances and allows the experimenter to get maximum gain and
 > > performance
 > > at a single frequency.
 > >
 > > German experimenters first published these ideas in the 1930's--- most
 > > of
 > > the publications are written in German but one can clearly see the large
 > > toroids they used on resonance transformers.  Tesla of course using some
 > > toroids to keep his ceiling exit point (his high antenna) from setting
 > > his
 > > wooden pole building on fire, but the German group was the first to see
 > > it's
 > > value to control the electrostatic field of the sec. inductor and reduce
 > > unwanted resonances."

-------------

 > > I think it's simply that the top loading made the equivalent circuit
 > > approach that of a single lumped LC.  Of course, it lowered the surge
 > > impedance as well which was almost certainly beneficial.
 > >
 > > Ed

	There are actually two separate messages there, the part above the line
is the original for which I take no credit and the one below the line
was my answer.  As for the "1/4 lambda point" from the discussions here
I would assume it to be the parallel resonant point.  I prefer to use
"self-resonant frequency".  I don't know whether "harmonic resonances"
are really observable with any significant capacitance across the
circuit since the losses for those modes are probably pretty high.

Ed