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Re: Guide to Primaries rev 1.01



Hi Tom,

<huge snip>
Correction (1):
> The question usually comes up as to how far apart from the outside 
> of the
> secondary should the primary begin. Malcolm Watts has made coils in which
> the flat pancake spiral was made of flat bar material and close wound about
> itself. The inside diameters of some of his coils have been less than the
> diameters of his secondary coils, and he reports good results from this
> arrangement. 

The coil was made in usual pancake style using 3/8" pipe. The inner 
diameter was about 5", outer diameter about 20". Resonator diameter is 
about 17".
    I have noticed no substantial difference between performance of a 
helical primary and spiral primary of the same inductance, using same 
cap and transformer, and coupled to the secondary with the same k. I
submit that the gap losses (reduced with higher values of k and/or
higher primary surge impedance) determine system performance if all 
other components are of good quality and unchanged in value. I think 
Bert's SPICE simulations bear this out.

<more snip>
Correction (2)
> Some people wind the secondary wires further apart. That usually lowers the
> Q of the circuit, but there are cases where space winding can reduce
> winding losses by reducing the proximity effects in the winding. One thing
> you do lose is inductance for the same wire gauge.

Reducing winding losses increases the Q, both in theory and practice 
according to my measurements.

Malcolm