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Re: An internal primary

Original poster: Finn Hammer <f-h@xxxx>


I have successfully used internal primary`s in 2 OLTC`s and also in 2 identical SSTC twins. So I have got 6 internals under my belt.

In OLTC`s, Solid state disruptive, there is no reason to use any precaution. The single turn primary fits elegantly and snugly into the base of the secondary coil.

I have had one problem with the internal primary in the SSTC. During one unintentionally long burst, the insulation on the primary wire toasted. I thought I had experienced a breakdown trough the secondary former material (1/4" PVC) but after stripping the sec. wire off, inspection showed no zoot under the windings. So the sec. was ok, still the pri. was toast.
I am going to use the internal of RG213 coax as primary wire in the future. In pulsed mode, with bursts up to 3mS and rep rates up to 500bps, I have no problems with internal primary even in SSTC.

Go for it! It`s sweet, easy to adjust coupling on the fly (which has been a great asset to learning about the effect of different coupling in twin coils, it being non intuitive) I have a nice design of an OLTC which you can see here:
and almost at the bottom of this page, there are pictures of the twin coils in the prototype stage.

Cheers, Finn Hammer

Tesla list wrote:

Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

Who was it who implemented an internal primary? Successfully, as I recall. I'm thinking of trying that but perhaps that someone, or someone else, would warn me off.

Ken Herrick