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Welcome to the list...
On 6/5/18 7:47 AM, James Janota wrote:
After watching Chris Boden with Billy and Trevor on their Geek Group
Youtube channel, and the opportunity that Chris directed me to this
group. As a first time builder of these types of devices, I'm hoping
that I can get assistance to direct me to the supplies I need and the
formulas to determine how to tune and understand the interactions
better. Hopefully, I can make a wireless transmission source to
experiment with. I'm not looking for a free lunch as I intend to do the
work, I just need to learn how to do the work. I've got my Amateur Extra
Radio Operators license, so I know antennas and a few things in regards
to radio operations. What I have seen so far on other TC builds, Tesla
coils are a different animal. So I'm a scoach out of my elements(pun
Intended).
Well - tesla coils are resonant circuits and terrible antennas...
Anyway, So far I have made a secondary coil with 2" pvc with 20"
length of coils of 26ga magnet wire hand spun without a jig. I've
counted @ 1000 turns.
This is good.
If this is like a 1/4 wave ground plane antenna,
the resonant frequency I have on the secondary is about 144Mhz. If I
take the formula of 468/frequency in mhz I should have 20" if I was to
make a 1/4 wave antenna. However, I may be over simplifying this or
altogether wrong.
yep - totally off base. The length of the wire is immaterial - it's
basically a lumped inductor with a fair amount of distributed
capacitance. You'll see, in some older literature, a contention that
the length of the wire (500 some odd feet, in your case) might be 1/4
wavelength, but that's just happenstance.
I'm thinking the primary coil and the secondary have
to be on the same resonance to be able to be dance partners. Hopefully,
I can make the primary out of 10 AWG solid wire, as I have an abundance
at my house.
or one of the many spreadsheets (I use one from Ed Sonderman that's
probably 30 years old by now).
The C of the secondary is a combination of the self C of the coil plus
your topload (some sort of toroid) - you want a toroid (dryerduct and
aluminum pieplate is common) so that the E field along your secondary is
reasonably even. And to help bring the resonant frequency down a bit.
Once you know that, and you've chosen some primary capacitors, you can
wind your primary. A flat spiral seems to be popular - good field
distribution and it's easy to adjust the coupling between primary and
secondary by raising and lowering the secondary, relative to the flat
primary.
Shoot for around a dozen turns on the primary, spaced about 1/2" apart,
with a 4-6" hole in the middle (1-2" clearance so you don't get arcs
between turns or between primary and secondary).
Other than that I was thinking of a NST output of 15kv may be
overkill for the secondary or does it matter? I did want to start off
small at first to get the basics down, then go bigger as my confidence
builds. I know I have a lot of homework on my hands and I hope y'all can
guide me through the process.
Your 15kV NST is perfect to start with. Going significantly smaller is
harder because things like spark gap losses are constant, so less power
means everything else has to work just right.
What are you using for a spark gap? I'm a fan of 3 pieces of copper
tubing in parallel with a fan blowing on it. I wouldn't suggest the "two
carriage bolts" approach. You want a large surface area for your spark
gap, so that you don't get hot spots.
