Hi Doug, Hi Gary,
Doug, you have realized, what was only meant as “my 2 cents”, in my posting, in a perfect way, while I was making only the following kind of “halfwave resonator TC’s”:
on my YouTube channel (hvchbs):
https://www.youtube.com/user/hvchbs/videos?view=0
... one can see my small flexible TC, in bipolar=1/2wave & 1/4wave mode:
https://www.youtube.com/watch?v=_GlSynTBlhY&t=1s
it has no variable coupling, i.e. of the kind mentioned in my posting
but a description of the “EBM-Museum Bipolar TC” can be had at:
https://hvchbs.zeitgenossen.ch/Downloads/EBM-Museums-TC-2.pdf
...On the other hand, I made a Twin, the Uni-Bern-Tesla-Twin:
https://hvchbs.zeitgenossen.ch/Downloads/UBTT-Betrieb.pdf
in which the primary is halfed in two flat spirals, positioned below
each of the 2 secondaries, and connected in series. By that way the
coupling can be adjusted for best coupling to each of the secondaries.
In the first of the 2 reports, at page 16 and pp. 18…&…19+ I’ve tried documenting, how one might look at the bipolar TC, in order to calculate it. The way I’ve taken is to assume the symmetry-plane in the middle of the system as a groundplane, and calculating one half of the bipolar only, as an ordinary quarterwave TC, as characterized by Paul Nicholson on TCML:
https://www.pupman.com/listarchives/2005/Mar/msg00573.html
This view leads to useful results in my case, and also lets me believe the proposed way of adjusting coupling is working –> a fact, Doug has demonstrated. I "think", in this case of a horizontal bipolar, there is no need or advantage for 2 primaries, but only for the secondary cut in 2 halves. I understand and concur with you, Gary, about some detuning of the TC will happen, when moving the 2 secondary halves, in order to change the coupling.
Best regards, Kurt
-----Ursprüngliche Nachricht-----
Von: Tesla <tesla-bounces@xxxxxxxxxx> Im Auftrag von Gary Lau
Gesendet: Samstag, 17. Oktober 2020 01:43
An: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Betreff: Re: [TCML] Coupling
Hi Kurt,
Splitting and separating the secondary seems like a great way to vary the coupling, but one must also bear in mind that doing that will vary the Lsec inductance and tuning. I can't think of a way to vary only the coupling on a bipolar coil, but I have never built one.
Regards, Gary Lau
MA, USA
On Fri, Oct 16, 2020 at 7:15 AM Kurt Schraner <k.schraner@xxxxxxxxxxx>
wrote:
> ...just my 2 cents: cutting the bipolar secondary in 2 independently
> movable halfs could enable the control of the coupling (see the
> ASCII-sketch):
>
> oooooooooooo
> __________________ __________________
> I__________________I I__________________I <---->
>
> oooooooooooo
>
> ...the primary can be either of a solenoid or a flat spiral.
>
> Regards, Kurt Schraner
>
> -----Ursprüngliche Nachricht-----
> Von: Tesla <tesla-bounces@xxxxxxxxxx> Im Auftrag von jimlux
> Gesendet: Freitag, 16. Oktober 2020 02:15
> An: tesla@xxxxxxxxxx
> Betreff: Re: [TCML] Coupling
>
> On 10/15/20 6:50 AM, Douglas Johnson wrote:
> > Thank you both, I think I know where to go from here on my current build.
> > My project is a larger bipolar than I have built to date. Secondary
> > is
> 3.5"
> > dia. X 24" with .015 mag wire. By the time I built the primary it was 6"
> > long and I was getting "runners" on the secondary. I think my fix
> > will be going to a flat spiral primary.
>
> On a bipolar, it's hard to control the coupling on a solenoidal
> primary sliding it one way or the other doesn't change the flux
> distribution very much.
>
> I'm not sure a flat is any better.
> _______________________________________________
<snip>
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