Re: [TCML] Tuning primary to secondary with a scope

[Jason Dunphy <jason.dunphy@xxxxxxxxxxx>]

I have never used a scope to tune a coil, but I have used my Fluke 
multimeter.  I have a secondary coil wrapped around some PVC and I have 
a number of primaries built in different sizes and different 
configurations.  The two are built separately so that I can quickly 
change them around and test things.  I hooked my voltmeter between the 2 
ends of the secondary and was able to read a voltage.  My input voltage 
on the primary is 3.5v from a PC driven function generator(Hantek).  
Yes, only 3.5v at 50 ohms resistance.  After sweeping for a frequency to 
get the highest possible voltage, I managed to get about 130v.  Now, I'm 
no genius or anything, but if an input at 3.5v gets me 130v, then an 
input of 15,000v should get 557,142V.
The most interesting things I learned about this experience:
1)  You can use off the shelf measuring equipment to get a better 
understanding of cause and effect between primary and secondary.  As 
long as you use low input voltage on the primary.
2)  You can physically manipulate the position between primary and 
secondary to see if it makes any difference.  With real time feedback on 
my meter I was surprised how little I had to move the primary to get 
differences of up to 25% in my secondary output voltage.  I was also 
surprised about the best position of the primary in relation to the 
secondary.  For instance, normally the primary is located at the very 
bottom of the secondary.  The secondary being wrapped on a PVC pipe 
mounted vertically.  Well, I moved my primary up about 1/5th the way of 
the secondary and obtained a 20% increase on the secondary voltage.  I 
had no idea.  The low input voltage makes it possible to handle the 
primary safely and with a lot of flexibility.
3)  You can compare on different styles of primaries and different 
lengths with great ease and speed.
4)  The best secondary length to frequency relationship came out to 
18%.  Tesla suggests an estimate of 25%  (Pretty good estimate for a man 
working in the 18th century)
5)  My Fluke meter has a frequency reader.  The frequency between the 
ends of the secondary are exactly the same as the input on the primary.
Admittedly, I only have had about 6hrs to play around on the above 
topic, but it is of extreme interest to me.  I would appreciate any 
thoughts or experimental results from other members.

Jason Dunphy

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