Re: An internal primary

["Tesla list" <tesla@xxxxxxxxxx>]

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

Ken,

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:
http://home5.inet.tele.dk/f-hammer/7.jpg
and almost at the bottom of this page, there are pictures of the twin coils 
in the prototype stage.
http://forum.4hv.org/index.php?board=7;action=display;threadid=1771;start=30

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