Re: Resonant Frequency?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mddeming@xxxxxxx 

In a message dated 11/17/06 2:07:46 P.M. Eastern Standard Time, 
tesla@xxxxxxxxxx writes:
Original poster: russell dischar <hightechredneck2005@xxxxxxxxx>

I built my first coil only a few days ago. I am attempting to build
another (them sparks sure are addicting) I was just wondering is a
higher or lower resonating frequency better. I am thinking about
making an 8" round by 24" tall secondary. but in the tesla designer
it has a very low resonant freq. im still just getting the hang of
this stuff, so any help is greatly appreciated.

Thanks
Russ


Hi Russ,

    There isn't really a "better" frequency. It's a matter of 
balancing component geometry:

 Bigger sparks require more power.
 More power means larger wire.
Larger wire means bigger coils.
Larger coil also means more inductance (L) and more inter-turn capacitance(C).
To store more of the energy in the topload, it must be larger.
Larger topload means larger total secondary capacitance.
Resonant frequency is inversely proportional to SQRT(L*C) so
Bigger L and Bigger C means lower frequency (f)
For voltage gain, you want L(sec)/L(pri) high, but if L(pri) is too 
low, primary currents get too high and heating losses increase. High 
currents can also kill caps and variacs.
Likewise, you want C(sec)/C(pri) to be low, but too small a C(sec) 
means small topload and poor streamers.
Very small coils can operate ~ 1+ MHz and very large coils ~50 KHz. 
If you're in between, you're probably OK. It's a balancing act.

Matt D.