Resonance Circuits and Resonance Systems

[Belfior]

Hmm I am searching for the resonant freq on my secondary. Can I just plug a function generator to my primary and crank up the frequency, or do I need some circuitry to protect the func generator? I mean that prim coil is just a short circuit.

What I was thinking is that I control the slayer exciter's transistor base with that function generator. Would that work?

[citfta]

Hi Mags,

Your posts about acoustical resonance reminded me of something my brother and I did back in the 1970s.  We had both just gotten into Ham Radio and lived about 200 miles apart.  At that time you had to learn Morse code and had to use it until you passed a higher level of license.  The band we needed to use because of our distance was usually pretty noisy especially in the summer time with storms and the static they caused.

Of course in those days there was no digital signal processing although there were such things as band-pass filters.  Neither of us could afford the expense of the added filters so we looked for an alternative.

We found an article in one of the Ham radio magazines that told how to make an acoustic filter.  All we needed was a cardboard tube from a roll of paper towels and a small speaker that would just fit at the end of the paper tube.  We cut some slots in the sides of the tube an inch or so from one end of the tube.  I don't remember the exact distance.  We mounted the tube with the end where the slots were down and the speaker on the top end.  This created a chamber that was resonant at a frequency that made the dits and dahs of the code nice and clear and rejected almost all the noise.  It was amazing to hear how much clearer the signal was with such a simple device.

Take care,
Carroll

[Magluvin]

Hi Mags,

Your posts about acoustical resonance reminded me of something my brother and I did back in the 1970s.  We had both just gotten into Ham Radio and lived about 200 miles apart.  At that time you had to learn Morse code and had to use it until you passed a higher level of license.  The band we needed to use because of our distance was usually pretty noisy especially in the summer time with storms and the static they caused.

Of course in those days there was no digital signal processing although there were such things as band-pass filters.  Neither of us could afford the expense of the added filters so we looked for an alternative.

We found an article in one of the Ham radio magazines that told how to make an acoustic filter.  All we needed was a cardboard tube from a roll of paper towels and a small speaker that would just fit at the end of the paper tube.  We cut some slots in the sides of the tube an inch or so from one end of the tube.  I don't remember the exact distance.  We mounted the tube with the end where the slots were down and the speaker on the top end.  This created a chamber that was resonant at a frequency that made the dits and dahs of the code nice and clear and rejected almost all the noise.  It was amazing to hear how much clearer the signal was with such a simple device.

Take care,
Carroll

Nice. Reminded me of a time we had a 12ft long piece of 6in pvc pipe and if you put a speaker at one end and slowly sweep audio freq there are points that the freq just jumps over some freq to an upper freq. Like it would not play that particular band of freq. Instead of a continuous freq increase there is a jump at that point and at other octaves and harmonics.

I am showing all this as proof of positive gain using resonance. Ive played with resonance circuits and I dont believe that I was going about it the proper way that took advantage of the gains of resonance. So I have to think differently on it all now. The speaker resonance gain needs to be examined as to why we can make really good use of the resonance gain there but we havent with resonance circuitry. Like a tesla coil. If it is resonant then it will put out more than a non resonant coil by great margins. There are many that dont take great notice of this gain in that transformer. What if resonance was added into our power grid transformers? Would we see the gain, input vs output, like we can see in a tuned tesla coil??

If our grid system is just running like a out of tune tesla coil, then what can we say about the eff of those grid transformers in comparison to say a tuned grid transformer? There has to be something to it and I believe we have to possibly try things differently somehow than we have been. So Im delving into the audio example to get a better feel for it all and hopefully something good comes out of it.

Mags

[itsu]

Hmm I am searching for the resonant freq on my secondary. Can I just plug a function generator to my primary and crank up the frequency, or do I need some circuitry to protect the func generator? I mean that prim coil is just a short circuit.

What I was thinking is that I control the slayer exciter's transistor base with that function generator. Would that work?

Belfior,

that prim coil is NOT just a short circuit, at a fairly low frequency it starts to be an inductor which has impedance (reactance) ontop of its DC resistance.
Surely at the frequency your slayer / kacher / tesla like sec. coil will resonate which will be around the upper hundreds of KHz.


So you can use that prim coil (disconnected from the circuit) to feed it with your FG and scan for the resonance frequency of your secondary coil (scope probe to
this unconnected sec. coil).

Or you can leave the prim coil connected and just use a cliplead wire and wrap that loosely 1 or 2 turns around the sec coil and feed that with your FG.
Depending on the number of turns on your sec. coil it will show a single high sine wave peak at resonance, even when feeding in a square wave.


But knowing the resonance frequency will not help much as the circuit you are using is an auto resonance circuit, it should automatically start resonating
at the resonance frequency of that sec. coil.
On the other hand, if it turns out that your sec. coil resonance frequency is above 3Mhz, then you have a problem as the 2n3055 has its limit there.

Using your FG to drive the transistor is not to be recommended (nor needed) as it probable WILL blow your FG frontend.
A buffer inbetween your FG and transistor would be needed, but again, this is not the way to go.


Regards Itsu

[Belfior]

But knowing the resonance frequency will not help much as the circuit you are using is an auto resonance circuit, it should automatically start resonating
at the resonance frequency of that sec. coil.
On the other hand, if it turns out that your sec. coil resonance frequency is above 3Mhz, then you have a problem as the 2n3055 has its limit there.

Well I kinda moved on already when I saw some Don Smith documents and circuits. So no more autoresonating. I used Smith's methods of calculating the secondary. If 16 MHz is the target freq I get 75,25 / 16 = 4,705m for the secondary length. I spent a day to get my secondary to 4,705m and primary to 1,176m like Smith.pfd tells me. Then some other dude says you don't need 1/4 wave length secondary and primary can be what ever...

So I sweeped my my 3 different primaries with my FG and oscilloscope shows 2,44MHz is the peak secondary voltage.

Now that I know this I might go back to the autoresonating version, since that freq is below 2n3055 specs and should work. Only thing I have gotten so far with the slayer exciter autoresonator is that if I turn the pot too low the transistor gets hot. I can't get anything on the scope no matter where I put the probes. I get some DC values and I thought the MHz is just out of my scope's range