Q, Coupling and things

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Q, Coupling and things
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 4 Nov 1997 20:58:42 -0600
Approved: tesla-at-stic-dot-net

From: 	Vivian[SMTP:V.C.Watts-at-btinternet-dot-com]
Reply To: 	Vivian
Sent: 	Tuesday, November 04, 1997 2:13 PM
To: 	Tesla List
Subject: 	Q, Coupling and things

Hi all,
        I joined the list back in May and just watched what was being said.
I read and read again Malcolm Watts article of 1995 in Wireless World.  In
September I left the list as I must admit I couldn't cope with all the email
and build my coil.  Well a few days ago I fired it up and it worked.  I'm
sorry to say I got big white sparks about 18" first time.  No breakout of
the secondary, nothing going bang.  I have yet to open up the gap to see if
I can get them longer but rain has stopped play as my earth spike is
outside.  So why am I writing?  Well you've got to tell someone haven't you.

Spec,

Neon Transformer    240v 50Hz,  10,000V 50ma
Primary Capacitor 15nF flat plate, polythene sheet (37Kv breakdown)
Primary coil 8" start, 10 turns  taped at 7.5, 1/4" copper pipe 1/4"
spacing.
Primary Inverse conical 30 degrees
Secondary coil 4.25" diameter, 20" long 24 A.W.G (0.54mm)
Secondary turns 870, Inductance 16uH
Toroid two stainless steal dishes, creates 16" by 10" toroid
Resonant frequency 270kHz

I have access to a Scope, signal generator and Meters so I was able to tune
it spot on before firing it up.  An interesting observation was the
secondary top load.  With the first dish in place you get a certain
capacitance.  With the second dish on top inverted the capacitance increases
significantly showing how isotropic the toroid and seemingly unaffected by
how close to the floor it is.

So now a few questions for the experienced.
I have read that the Q of the secondary should ideally match that of the
primary.  In Malcolm's  article It tells you to measure the frequencies at
the 70% of Max points of the resonant freq..  But not what to do with them!
Guessing is it Fres/(Fupper-Flower)?  I can't find my old electrical books.
My values are
Secondary 70% points 272 and 278Khz
Primary 70% points 271.3 and 273.5, centre 272.4

When the secondary is in place, the coil has a double humped response of
253Khz and 298 kHz.  Can anyone explain how this is?  Is it the two coils
now having different resonant frequencies?

I hear about coupling.  Is this akin to matching the source impedance to a
load?  If so take the two extremes.  No coupling = no power transfer.
Overcoupling is equivalent to what?

Has anyone ever tried to focus the sparks from TC.  I have some powerful
magnets and was wondering if they can be formed to focus the sparks like the
guns in a TV tube.  Or will the AC nature of the spark screw it up?

Regards

Viv Watts UK