Re: Half wave/ bipolar coil

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Original poster: jdwarshui@xxxxxxxxx 

Hi: Lee

Jared again, with advice on a primary for your half wave:

 The only gain you would get by splitting your half wave secondary in
two is that you would be able to independently adjust the coupling.

 Our first half wave was designed this way and it was a mistake. When
you split your secondary into two parts you are begging for flashover
near the current nodes, as the exposed edge of the solenoids now
represents a sharp edge with a minuscule radius.

Solenoid primaries are easy to make by winding fresh copper tube about
round objects. You can change the coupling by stretching this spring
out  a bit. It will change the inductance as you stretch it so you
would need to re tap afterwards.

I would recommend a 20inch form for your primary and keep the winds
about 1/8 inch to 3/16 inch apart. The more primary winds you can
squeeze in the better off you will be.

 It is easy to tune a primary with a lot of turns. If you have 20
turns and you are off by one turn you will hardly notice. But with six
turns you will be struggling to find the sweet spot.

 The leads to the primary become a big hunk of the inductance when you
only have six turns, very difficult to tune around this.

We have built a few coils with 18  to 20 turn primaries, and have very
much liked the results.  I suspect that larger primaries cut down on
current density and thus reduce resistive loss.


Good luck from Jared