# Re: How to tune? (fwd)

---------- Forwarded message ----------
Date: Sat, 30 Jun 2007 22:47:26 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: How to tune? (fwd)

Hello Drake,

The guy sitting in the statue of Tesla at Niagara Falls is our
illustrious ex-moderator, the famous Terry Fritz! You also gave a
half-name (Gary Lashus?), I can only imagine is intended to read Gary
Lau. It's very possible Gary or Terry had a document with a step by step
tuning procedure, but I can't seem to find it.

With that said, there are various methods. There is of program
prediction where you insert your coil dimensions and out pops the
primary tune tap position for your coil.
http://www.classictesla.com/java/javatc.html

There are also tuning via measurement of signals and trial and error
(which is actually quite good).

Here is a method noted by Antonio Carlos M. de Queiroz:
-------------------------------------------------------------------------------
The method that I use is:
Connect a 1 Ohm resistor across the output of the signal generator, to
have a low-impedance signal.
Connect the signal generator where the spark gap would be, with a
low-frequency (1-10 kHz) square wave of maximum amplitude.
The secondary coil and top load shall be in place. Ground can be at the
oscilloscope ground.
Look at the voltage over the primary capacitor, or over the primary
inductor, at the transitions of the square wave.
Tune the system until you see full notches, like in this photo:
http://www.coe.ufrj.br/~acmq/tesla/tefpreg1.jpg

This is the ideal tuning without breakout. To account for streamer load,
connect a wire to the top load with the length of a reasonable streamer
and tune
in the same way. Mark the two positions found. The best point will be
somewhere between these.
Note that the waveform shows also the resonance frequency of the two
tanks, and allows the measurement of the coupling coefficient.
-------------------------------------------------------------------------------

You can also tune by trial and error. This typically indicates that you
tap a bare wire primary at various positions along the winding of the
primary which changes it's inductance and thus, the fundamental
frequency of the primary coil to math the fundamental frequency of the
secondary resonator. When this procedure is used (the trial and error
procedure), the cap is usually a fixed value and only the primary is
varied (because it is mechanically the easiest variable).

There are a couple setup procedures which help this process. First,
run the coil at about half power. There are two easy ways to do this:
1) Using a variac, adjust the variac to 1/2 power.
2) Use 1/2 the number of gaps in the static gap setup to lower the

As you tap the primary winding (if your other parameters are now way off
base), you'll find the longest spark lengths near the optimal tap
position. Some coils (small L primarys) are more finicky than others
(large L primarys). You'll find out how finicky your coil is by tuning it.

So, lets say you've tuned to the long spark length. Now you need to
observe the coil running. If your getting any arcs along the secondary
or from primary to secondary, there are problems. If primary to
secondary, you'll need to increase the proximity between coils. If
racing arcs, you'll need to raise the secondary (or lower the primary)
to again increase the proximity in that particular direction of the two
coils.

If it's running fine without those pesky problems, you may want to lower
the secondary down into the primary until you "see" those problems
occur, and then raise the secondary to just get outside the racing
sparks. Once you've done that, your tuned for low power.

Yes, I said "low" power. Now you'll need give the coil all it's got
without limiting the power. You may find that the coil is having racing
arcs at high power. So, definitely go through the tuning process one
more time regardless. The low power tuning helps us in the long run. If
something is connected wrong, or whatever, it may prevent the coil from
serious damage.

Longer sparks often load the coil causing a frequency shift during
normal running and likely the primary will require a little added
inductance to offset the frequency shift. This can be often times termed
as running "high on inductance" a few percent (maybe 5% to 8%, sometimes
more if the primary coil is several turns). What this means is that from
when it is detuned high on inductance to offset streamer loading. You
might be surprised at the number of coilers that actually run high on Lp
(and some without realizing it). But, many do realize this. I was very
surprised to find out during some TSSP testing that everyone else
testing was also tuning the coil high on inductance for "best coil
output" and "a nice running coil". I'm not even sure if they all
realized it. It was eye opening to me. Following this realization, I
threw into Javatc a detuned output in the primary table to identify if
the coil is high or low on inductance and how much via a percentage.

Not sure if any of this will help. Hopefully someone will post the page
you lost.

Take care,
Bart

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Fri, 29 Jun 2007 22:03:22 -0500
>From: Drake Schutt <drake89@xxxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: How to tune?
>
>Hey everyone- I'm getting to the point where my coil is almost done and
>realized that I lost a very important webpage link.  It was a tutorial on
>how to set up and properly tune your coil and it was great!  now it's lost
>:(   If anyone knows where I can find this or a similar step by step guide
>to setting up my coil I would be obliged.  I think it might have been on
>gary lashus' (can't really remember his name) page but I really can't find
>it.  All I remember is the first page on his site was him sitting on some
>huge statue.
>
>thanks a million
>drake
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