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Registered Member #3026
Joined: Fri Jul 23 2010, 02:46PM
Location: Los Angeles, California, U.S.A.
Posts: 54
Gentlemen;
Are there any advantages/disadvantages to choosing a higher or lower resonant frequency for a tesla secondary? I simply wound 900 feet of #28 on a three and a half inch PVC, 18 inches long (no calculations used) and the resonant frequency turns out to measure 248KC. My coil works fine, but should I have aimed for a higher frequency? I’m still learning on my first coil. Great site, thank you, all!
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
radioman wrote ...
Gentlemen;
Are there any advantages/disadvantages to choosing a higher or lower resonant frequency for a tesla secondary? I simply wound 900 feet of #28 on a three and a half inch PVC, 18 inches long (no calculations used) and the resonant frequency turns out to measure 248KC. My coil works fine, but should I have aimed for a higher frequency? I’m still learning on my first coil. Great site, thank you, all!
This question is impossible to answer when you give us very little information to work with, we need to know every little detail about your tesla coil in order to answer the question fulfilled.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
A few random thoughts;
For a typical entry-level spark gap TC using an NST (or OBIT etc.) the primary capacitance is pretty much fixed so as Fres increases the primary current increases, proportionately increasing primary losses/stress/noise. (capacitor, inductor and most importantly spark gap)
For a given secondary winding height and diameter, reducing Fres requires thinner wire, increasing losses. I don't think that secondary loss is as important as primary loss as the secondary rarely gets hot, compared to the primary components.
The 'Q' of the secondary is not important as once the fun begins the 'Q' drops dramatically.
Lightning is not 7 Hz, the Schumann resonance of the Earth's atmosphere is. Slow-motion lightning videos (especially the 4th one across) Schumann Resonance
I believe that the lower the Fres the longer the sparks (for a given NST/primay cap etc.) but the benefit is lost when the TC becomes much larger than the arcs/sparks (12" sparks from a 12" coil is visually more impressive than 15" sparks from a 24" coil) I also think that the quality of the primary components has more influence on 'performance' than Fres, so spend your effort on reducing primary losses and tuning, don't worry too much about the actual Fres.
You can vary the secondary topload capacitance/size to see for yourself what happens with various Fres.
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