Re: Quarter Wavelength Frequency

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FIFTYGUY-at-aol-dot-com 

In a message dated 7/24/04 1:41:58 PM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:

 > Bearing in mind that these are measured values, we do seem to have
 >  the real coils tending to a high velocity factor as h/d increases.
 >
 >  Is there anybody out there with a coil with h/d > 10 ???  If so,
 >  we want your measurements!

     A real-world source for very high h/d coils comes to mind: spiral-core
spark-plug wires. Used to minimize EMI with low-resistance wire, instead of
using straight high-resistance wire. Easy to buy from performance auto 
suppliers.
And conveniently rated for high voltage use.
     Also some uneducated thoughts:
     As the h/d increases, I'm guessing the vel factor and such don't approach
a straight wire because the fields are actually approaching right angles to
their "straight-wire" orientations. An infinitely long zero-radius close-wound
coil will have the magnetic field parallel to wire's axis, not perpendicular
to it as with the straight wire it resembles.
     And in another post:

     >To reach this straight wire velocity factor, our models and
     >calculations would have to allow the pitch to increase to
     >infinity as well as the h/d ratio.  This they do not do.

     So as the pitch increases, you are "stretching out" the coil back into a
straight wire. But doesn't space winding decrease the "Q" of a coil, and
therefore make it less efficient as an inductor, which is what you would 
expect
from effectively unwinding one?

-Phil LaBudde