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Re: Big tc article

   Brad,

       MANY people here are familiar with 'Big TC'.  I fist built this
       coil 15 years ago, with miserable results.
After a combined effort from everyone on the list, I FINALLY got
EXCELLENT results.
       The default configuration works great except for one component --
       the primary coil.  The helical
wound coil they promote has horrible coupling characteristics with the
tall skinny secondary.  I wound a replacement primary with 3/8" copper
refrigerant tubing in a 30 degrees archimedes spiral.  However, since
you have not constructed yours yet, and are not yet obligated to use
the secondary they recommend -- Change it!!  The secondary they promote
has an aspect ratio in excess of 8.  If this coil were cut in half, it
would probably produce better results.  If you are after the aesthetic
beauty of this coil, and the tall intimidating secondary, then go for it!
... just be prepared for the headaches!
     The glass plate capacitor works great, I believe it has a value of
     around .027mfd.  However, I switched
to a bank of beer bottle cpacitors for greater tunability.  Also, the
stock capacitance usually dicatates a very large inductance, and you
often find yourself 'tapped out' completely at the outtermost turn of
the primary.  Also, a coil this size would LOVE a liitle more power than
9kv... I am running mine with a 15kv 60mA neon.   Of course the gap MUST
be replaced at this power, and I would highly reccomend it for yours.
The gap they reccomend has terrible quenching characteristics; in fact, my
gap was -impossible- to quench once I switched to the bigger transformer.
I recommend the cylindrical static gap with a muffin fan.  It's design
can be found on the FTP site.  Also, the addition of a toroidal discharge
terminal to the coil boosts performance greatly.
    Gee... I guess I am saying that the coil is an absolutely horrible
    design.  If you are satisfied with 24"
streamers, build the coil per specs and change the primary.  If you
want to get closer to 48" to 60" discharges, dump the design completely.
My struggle of upgrading components one at a time did teach me a great
deal about coiling -- but I feel you would be better to observe the list
for a couple of weeks, absorb all of the wonderfull info, and then design
a coil yourself!!

    Just my opinion, I'm sure the others will have comments on the
    coil also!!

George Dodworth
gpd104-at-psu.edu