Re: Spherical vs. toroidal top loads on tube coils

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Shad Henderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi Dave, All!

  The dimensions for your tube coil are about the same as mine.   I recently
tore mine down to re-build it (I got tired of looking at wire nuts and
electrical tape), and it's about 1/2 done.  Painted and clear-coated
everything that needed it, and I am proud of it's appearance so far.  Not
perfect, but a vast improvement over what it was.

   I have found that the toploads I used (2, 3, and 4" spheres), and 1.5x6"
spun toroids, made little difference on tube coil output, but made a world
of difference in tuning and reflected "trash" back into the house.  The tube
coil couldn't break out from a 1.5" toroid or a 2" sphere (flagpole ball) on
it's own without a breakout, but running the coil at 1/2 to 3/4 full power
with no breakout would light up my garage flourescents really well, though
it also dumped a *lot* of RF trash back into my house wiring.  I'd use as
little topload as you can. The whole topload for my coil I'm rebuilding is a
3" length of 10x32 brass rod with a little ball (maybe < 1/4" diameter) on
it, and I'll put a drilled& tapped mouseball on the bottom of the brass rod
(inside the coil) to prevent unwanted breakout inside the form.

Some info I got from the List that has proved helpful,
    Put the grid coil below the primary.  I did that, and the coil worked as
good as ever, minus the corona from the grid coil windings that kept setting
my primary form on fire.
    A variac to run the plate tranny is almost a Must.
->A variable cap is an excellent tool for tuning the coil - if you don't
have one, stay tuned for info on my prototype. <$10, ~300pf to 1.2nf range.
   Good Grounds!  Performance on my coil sucked till I found the poor
connection to the filament tranny's centertap.
   Good quality solder joints and heavy, short conductors for the tank
circuit.  Low inductance is your friend, as is ample room on the conductor
for RF to circulate on.  :)

  Keep us posted on your progress!  Tube coils rock, and are a great way to
get the Ozone fix without all the crash and bang.  Plus the streamer from my
12/30 coil won't melt 20ga wire the way my tube coil can ;)


Shad


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, October 02, 2001 10:30 AM
Subject: Spherical vs. toroidal top loads on tube coils


> Original poster: "David Speck by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<dspeck-at-relex-dot-com>
>
> I'm pondering the construction of a tube coil using a pair of 833As, and a
> roughly 4: diameter
> x 24" long secondary.  I've noted that several current VTTC designs use a
> small toroid on the
> secondary, just like a SGTC.
>
> I don't happen to have a small toroid at the moment, but recently ran
> across a fine spun
> aluminum sphere about 7" in diameter.  Does anyone have any idea how a
> spherical topload would
> compare to a toroidal topload of the same general size?  Is there any
> reasonable chance of it
> working?
>
> Thanks -- I'll look forward to hearing any ideas about this.
>
> Dave
>
>
>
>