Tuned Circuits Article - re: Impedance

If you have a cavity or long tube then the coil of the GDO can be stuffed in a hole and tuned to give a dip at the resonant frequency. This practical for frequencies up to about 750MHz where conventional coils are practical.

When I was testing my NIDO tin resonator I used by GDO coupled into the resonator to determine the resonant frequency of the resonator. I did not want to make a hole in the tin.

A diode probe and generator can be used where there are input and output connectors.

Practically, the method of test can be different, depending on the form of your resonator.

Very best regards from Harry

I have a question about resonance to. I am looking for a circuit that I can build that will give me the resonant frequency of an object like a water pipe or what ever.  As far as coils and capacitors go I should be able to use a diode and look for the highest voltage or use your GDO, right?
 Here is a web page that has a lot of interesting things on it that make a person think maybe we don't know as much about electronic and electricity as we think we do.  I have read a lot about the the things that were removed from the electrical theory and it looks to me like some of those old scientists 130 years ago were on to something.  I think we are ignoring some of these forces because we don't understand them and they could very well have an effect on a lot of things.  
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Hi Greg,
Yes, at resonance the impedance of the capacitor and inductor are equal.

<---- fact 1 ---->

If you therefore test a 100pf capacitor and adjust the frequency you will
find it has an impedance of 1000 Ohms at 1,591,549 Hz.
Similarly
If you therefore test a 100uH inductor and adjust the frequency you will
find it has an impedance of 1000 Ohms at 1,591,549 Hz.

100pF will therefore have a resonance frequency of 1,591,549 Hz when placed
in series/parallel with a 100uH inductor.

<---- fact 2 ---->

If you halve the inductor and double the capacitor then the resonant
frequency will remain a constant.

<---- fact 3 ---->

If you multiple the inductor (uH) by the capacitor (pf) you will get a
constant value for that frequency:

100 x 100 = 10,000, which is the "index" value for 1,591,549 Hz

If you re-calculate for 1,500,000 Hz (1.5MHz) then your "index value" will
become 1,111,111

<---- fact 4 --->

There is a constant "index value" for every frequency but only for one given
impedance.

<---- end of facts ---->

So if you have a table of 1KOhms values, then you can easily calculate an
inductor, if you know the capacitor. For example, at 1.591MHz and a 68pf
capacitor, the inductor required for resonance is 10000 / 68 = 147uH.

In my article I gave the values for 500 Ohms impedance but showed how it is
calculated.

Does this clarify things a bit?

Very best regards from Harry - SM0VPO

Greetings Harry SM0VPO,

I've been looking at your article on Tuned Circuits and I am very curious about where the 1000 Ohm impedance figure comes from (in Method #3) when selecting a capacitor and inductor of "equal" value (in pF and uH) - taken from the square root of the number in the chart... or about "500 Ohms(ish)" in your "Method #1" example. It was my understanding that at resonance (where capacitive and inductive reactance cancel each other out), a tuned circuit (parallel circuit) (using ideal components w/ no R) had infinite impedance, or zero impedance (for a series circuit).  This has sparked some debate among a small group of us here in Carson City, NV. Any help, or a more detailed explanation about where those figures come from would be sincerely appreciated.

TNX and 73, -Greg WB6DAI

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