Build a Tesla Coil (the way Tesla built them)

Calculations and Preparations

Starting guide: wind a coil with a height-diameter ratio around 1:1 with an air-gap between turns of at least half the wire diameter.

Calculating Wire Length https://Hakasays.com/DollardTeslaCoilCalculator
or:
297/F = L
F = frequency in Mhz
L = wire length in feet

Note that due to dielectric effects, a Tesla Extra coil has a higher frequency than is predicted by normal 1/4 wavelength formulas. We call this the ‘velocity factor’ and it is directly related to the height-to-width ratio of the coil.

Framing Material Selection

Best: UHMW, HDPE, LDPE, PTFE(Teflon), PP
OK: Polystyrene
Meh: Polycarbonate, Acrylic, Epoxies, PVC, Wood

Sadly, this means that hardware store plastic sheeting just aren’t going to cut it. But HDPE buckets from the paint section…….

3/16″ to 1/4″ thickness works good for coils 3-12in in diameter
Plastic sheeting is usually sized in 12×12″ sections, so cost-efficient diameters are around 5-5.5″ and 11-11.5″
White/light plastic have lower loss characteristics
Material selection has a higher impact at higher frequencies

Wire selection:

The general goal here is to get the lowest resistance practical.

Obviously few people can afford 100ft of 0 gauge copper bus-bar to wind a coil, so compromises must be made. Generally we recommend not going below 20awg though as the loss characteristics begin to compound making a very high Q coil difficult to achieve.

Silver-coated Teflon wire
Silicone-coated wire
Litz wire
Coax cable can also be used to create a large effective diameter coil by using the outer ground conductor (per Eric Dollard)

Coax cabling can also be used to create a large effective diameter coil by using the outer ground conductor (per Eric Dollard)

Construction

‘Jigsaw method’

Cheapest/simplest tools required:

Drill + drillbit set
Jigsaw / router / hand saw
Hand files

Cutting the top+bottom disks. Best practice is to use a circle-cutting jig on a jigsaw/router, but many techniques could be used to do this.

Notching the disks. Notch width = thickness of your material. Depth is not critical but should be at least 2x the thickness of the notch.

Notching+grooving the vertical risers. This is the best time to cut the wire grooves, which can be done with a hand saw in a pinch.

Now you’ve finished your first Tesla Coil. What do I do with it?

Testing and Tuning (coming soon)

6 responses to “Build a Tesla Coil (the way Tesla built them)”

jeff walkerw says:

August 11, 2022 at 3:47 pm

Now that I can make the described coil, what else do I need to have a compact power supply?

Reply
- hakasays says:
  
  August 24, 2022 at 6:52 am
  
  For testing you can use a function generator or HAM radio transmitter (if it is on the right frequency).
  
  The most efficient power supply would be a class E amplifier, which would look like this:
  https://www.researchgate.net/figure/Schematic-of-69MHz-Class-E-amplifier_fig2_320623200
  
  The inductor on the right would be your Tesla Extra coil,
  instead of a filter cap and resistor you would have a bridge rectifier and capacitor filter.
  
  Feel free to email me @ bakahsay@gmail.com or discord @ Hakasays#7694 and I can try to help you get something together. 🙂
  
  Reply
Breck Alderson says:

August 16, 2022 at 12:07 pm

Hi Hakasays (I don’t know your name). I am utilizing your TeslaCoilCalculator to build my first tesla coil. There are two spacing parameters listed in the output: Wire Spacing and Ideal Wire Spacing. The Ideal Wire Spacing is much closer than the Wire Spacing parameter. Which parameter should I use to wind my coil?

Where are the detailed calculations for the calculator output stored? May I have access to these formulas and the associated references?

Thanks and have a great day,

Breck.

Reply
- hakasays says:
  
  August 24, 2022 at 6:48 am
  
  The equations were pulled from Eric Dollard’s “crystal radio initiative” project, which I believe is an Ebook and a couple videos.
  Some useful bits here: https://kupdf.net/download/crystal-radio-initiative_5af89140e2b6f5131fd54e23_pdf
  
  Ideal wire spacing is 62% of the wire diameter. So a 1mm wire would be 1.62mm from center-to-center. (Wire spacing has a bug that I haven’t patched-out yet, sorry about that)
  
  I do intend on posting the formulas driving the calculator online at some point, just been busy with other side-projects like the telluric work.
  
  Reply
Partha Sarathi Mishra says:

January 29, 2023 at 4:14 am

Hi

I tried winding a coil over a normal mailing tube instead of plastic chassis, with quarter wave length (approx 4m). I connected the positive end of function generator to the bottom end of the coil and the negative end left free.

But unfortunately even changing frequency +- many times, I failed to establish any standing wave with resonance.

Is it good to connect the signal generator directly or any amplifier needed?

Reply
nicholas skelly says:

February 1, 2023 at 4:52 am

just seen your video presentation and it fills me with a new hope that an original design will allow the magic we are looking for. I will post me example and results. I have made various experiments with the bifilar coils and i beleive this will give us what we are looking for. It could also give us the power needed to replemish the run battery or capacitors?

Reply

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