Re: [TCML] Secondary Coil: Wire Gauge and Number of Turns [FIX]

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

On 7/4/13 8:18 AM, Phil Tuck wrote:
> Q Factor:
> A unitless number which you can use as an indication of how efficient a
> tuned circuit is (my 'off the top of my head' defination - others will do
> much better with that)


Not bad in a qualitative sense.  Q comes from "quality"

It's the ratio of the stored energy over the energy lost per cycle, and 
as noted, the higher the Q, the longer the bell rings (because you're 
not losing as much each cycle).

In a practical TC system, you lose energy from two places: one is the 
internal losses (resistive losses in the coil), the other is conducted 
or radiated away (sparks!)

A typical Q for a TC is in the 10-15 range


You can calculate the Q of a component, e.g. an inductor, as the ratio 
of reactance/resistance.  That results in a number with the same "scale" 
as the Q of a tuned circuit having that Q, and for situations where 
either L or C is lossless, that makes it nice. For most RF situations, 
like tank circuits or antenna traps, the C is often air dielectric and 
essentially lossless, so the inductor Q is everything.  At VHF and up, 
dielectric losses start to get bigger.


For some circuits (RLC resonance) there's a relationship between the 
bandwidth and the Q.. Q = center Frequency/half power bandwidth.

However, that ONLY applies for fairly simple 1 R, 1 L, 1 C type 
circuits.  It catches antenna designers, for instance, because complex 
antennas have many R, L, and C, especially if you have a multipole 
matching network.  A simple dipole near resonance is well modeled by a 
RLC. Get away from resonance, or near a higher order resonance (2x or 3x 
frequency) and it doesn't work as well.





_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla