1. 1989. This is a spark gap Tesla coil running on a 12-kV 30-mA neon sign transformer. The neon transformer is located several feet away from the coil, beyond the left side of the photo. The primary spark gap uses a blast of compressed air for quenching.

2. 1989 - Spark gap Tesla coil driving an experimental top load designed to reduce eddy current losses. The idea has some merit but the top load would need to be designed much better than this (smaller conductors and closer together to simulate a solid smooth surface).

3. 1989 - A collection of several different Tesla coil resonators. Numbers 1, 2, 3, and 4 have the same length of wire (the surface areas of the coils are the same). This was to evaluate the various coil parameters with different aspect ratios. There are two number 2 coils to conduct experiments with running two coils at the same time and with the same frequency (the phase of each coil changing though). Number 5 is wound with Litz wire. Number 6 is a figure “8” coil (wound with two turns on one former in one direction, followed by two turns on the other former in the opposite direction, continuing for the entire length of the resonator). The figure “8” coil worked as good as any other coil when being base driven. Numbers 7 and 8 have the same dimensions as number 3 but being wound with larger diameter wire (number 7 is close-wound while number 8 is space-wound). The antique radios include: 1 - Norden-Hauck Super 10 (s/n 66) from 1926 (TRF), 2 - RCA Radiola Super-Heterodyne AR-812 from 1924, and 3 - Golden-Leutz Super-Pliodyne 9 (s/n 123) from 1924 (TRF).

4. 1989 - Vacuum tube Tesla coil system with two coils being base driven. The two coils are driven 180 degrees out-of-phase with each other, resulting in the corona discharges/streamers attracting each other.

5. 1989 - Vacuum tube Tesla coil system with two coils being base driven. The two coils are driven with the same phase, resulting in the corona discharges/streamers repelling away from each other.

6. 1990 - Solid state base driven Tesla coil designed for 53 kHz. This was one of my first solid state Tesla coils and it was described in some detail in my 1991 book Modern Tesla Coil Theory. The driver was originally an LH Research 5-volt 200 amp full bridge power supply. This driver would put out 1 kilowatt average power continuously and several kilowatts peak running in pulsed mode. I designed it with Automatic Frequency Control because I thought that it was important to drive a purely resistive load. Afterwards I found out that AFC was not that important. The power for the full bridge was +/- 160 volts DC with two 4000 microfarad capacitors for filtering. The output high frequency of the driver could be pulsed at a variable repetition rate and duty cycle. First light in CW mode was June 10, 1989. First light in pulsed mode was June 12 and June 13, 1989. My vacuum tube base driver is in the background. The vacuum tube driver used two each Eimac 250-TL tubes in parallel.

7. 1991 - This is the Corona Coil Model 1 Tesla coil. This Tesla coil was featured as a construction article in the September, 1991, Radio-Electronics magazine. It was also featured as a construction article in the 1993 Electronics Experimenters Handbook. This photo shows the Tesla coil sitting on top of a counterpoise. The counterpoise is constructed with many wires radiating out from a central point, the wires being connected only at the central point to help eliminate eddy currents. The current in the counterpoise was a good percentage of the current in the resonator and this was helping to reduce the external electromagnetic field. The peak output voltage here is approximately 94,000 volts. First light was December, 1990. Here is a schematic diagram.

8. 1991 - Close up view of the Corona Coil Model 1 Tesla coil driver. The heart of the circuit is the SG3524 pulse width modulator chip, hard wired for a duty cycle close to 45%. This is a half bridge circuit using two bipolar power transistors. Somewhat outdated for today’s standards, but this was state-of-the-art in the late 1980’s! If the PC board was purchased from me it would be identified on the solder side by “Corona Coil Model 1 Tesla Coil 11-29-1990.”

9. 1991 - The Corona Coil Model 2 Tesla coil. This is the big brother of the Model 1, utilizing a full bridge circuit and higher output voltage of the driver. The corona discharges/streamers in this photo are around 15 inches long, yet the resonator peak voltage is only about 58,000 volts (lower than the resonator voltage of the Model 1 shown above). Why is this? Because the output voltage is controlled by the type of discharge electrode. In this case it is a pointed rod. Corona starts at a relatively low potential, and any additional energy forced into the resonator goes into the discharge instead of increasing the stored energy. The resonator acts like a series lumped circuit when operated at the 1/4 wave frequency. L = 165 mH, C = 12 pF, producing a resonant frequency of about 113 kHz. Xc = Xl = 117 k ohms. The output voltage equals the current forced through the reactance multiplied by the reactance, and in this case it is .5 amp peak times 117 k ohms, equaling approximately 58,000 volts peak. A visual clue to the actual voltage is the streamers. Note that the streamers are only attracted to the grounded rod above the resonator when they get within just a couple of inches of the grounded rod. Most of the streamers are longer than the distance between the discharge electrode and the ground electrode. First light was February, 1991. Here is a schematic diagram.

10. 1991 - Tesla coil winding machine for making the Model 1 and Model 2 Tesla coil resonators. The wire is 30 gauge and it is close-wound on a 5-gallon bucket for a length of about 10.5 inches. I manufactured somewhere around 100 of these resonators to fill orders generated by the two construction articles (the September, 1991, Radio-Electronics magazine, and the 1993 Electronics Experimenters Handbook).

11. 1992 - This is a schematic diagram for a 3-phase Tesla coil system controller. The phase of one to six resonators can be controlled from this circuit. The phase data for the resonators is stored in the 2532 EPROMs. The 7414 forms the clock oscillator and the clock is divided down by the 7492 and 7473 counter, which selects the memory addresses of the EPROMs. The output data of the EPROMs is fed into 7407 open-collector circuits to drive the main solid state resonator drivers (the SG3524 is removed from the Model 1 or Model 2 drivers and the open collector outputs from this controller takes over).

12. 1992 - This is a truth table for some of the data programmed into the EPROMs. Several different phase modes can be controlled (the different modes are selected by DIP switches). In this table the six coils are programmed for 3-phase rotary fields in a clockwise direction (three coils can also be controlled with rotary fields with this program). Other modes included 3-phase rotary fields in a counterclockwise direction, driving all six coils with the same phase, driving 3 coils with one phase and the other three coils 180 degrees out of phase, etc.

13. 1992 - First light of the 3-phase Tesla coil system using six resonators - July 4, 1992.

14. 1992 - This is the physical setup of the first 3-phase Tesla coil system. The yellow resonator, not part of the 3-phase system, was on the cover of the September, 1991, Radio-Electronics magazine.

15. 1992 - Here is a photo of me holding a florescent light near the 3-phase Tesla coil system.

16. 1992 - My son, Taylor, and me standing under a bunch of freshly made resonators. Most of these resonators were built for orders generated from the article in the 1993 Electronics Experimenters Handbook.

17. 1992 - My son, Alex, and me near the Model 1 Tesla coil with a top load. The base driven solid state Tesla coil is the most versatile Tesla coil ever built. The driver frequency can be changed instantly over a wide range of frequencies with the adjustment of a small potentiometer, which can immediately accommodate a wide range of resonators and top loads.

18. 1992 - Another photo of the Model 1 Tesla coil with a different top load. L = 165 mH and C = 19.4 pF, producing a resonant frequency of 89 kHz. 1.5 amps peak is forced through a reactance of 92 k ohms, producing a peak voltage of approximately 138,000 volts.

19. 1992 - Another photo of the Model 1 Tesla coil, this time with a pointed rod as the top load. The peak output voltage here is approximately 50,000 volts.

20. 1992 - This is a 5-gallon bucket resonator with small sockets mounted in series with the wire about every inch across the length of the resonator. Incandescent lamps or back-to-back LED’s can be inserted in the sockets for the purpose of monitoring the average current at different locations in the resonator. This photo has LED’s in the sockets. The resonator is being base driven (low power) at the 1/4 wave resonant frequency and the LED’s indicate that the average current is linear throughout the length of the resonator. What does this mean? It means that at the 1/4 wave resonant frequency the resonator acts like a series lumped RLC resonant circuit! The high current at the top of the resonator is flowing throughout the air surrounding the resonator. This is how all Tesla coils work when operated at the 1/4 wave resonant frequency (including base driven resonators or magnetically coupled resonators). High voltage is produced by forcing a high current through a high reactance. For best results, you want maximum current through every single turn of the resonator!

21. 2000 - The 3-phase Tesla coil system was fired up again after eight years in limbo. Hear is a close up view of the 3-phase controller and three solid state drivers.

22. 2000 - The complete 3-phase Tesla coil system setup with three resonators. For a rotary field the resonators are driven at 120 degrees phase difference from each other.

23. 2000 - Three resonators riven with 3-phase. The power for the drivers in this photo was 1/2 wave rectified 140 volts AC. When a discharge starts to appear in a multiple resonator system like this the total energy from all the resonators tends to get dumped into the single discharge. Even though the resonator with the small sparks looks like it is wimpy, it is contributing energy to the larger sparks.

24. 2000 - Similar to the photo immediately above, but now the sparks are between different resonators.

25. 2000 - Three resonators with larger top loads being driven with 3-phase. The source of power for the drivers is 1/2 wave rectified 140 volts AC.

26. 2000 - Three resonators being driven with 3-phase. The source of power for the drivers is a 20,000 microfarad capacitor charged to 200 volts. There are several bursts of CW energy in this photo. Here is a similar photo.

27. 2000 - Three resonators being driven with 3-phase. The source of power for the drivers is a 20,000 microfarad capacitor charged to 200 volts. This photo shows one burst of CW energy.

28. 2000 - Photo of me with the 3-phase controller driving two resonators. In this photo the two resonators are being driven with the same phase. There is a single burst of CW energy. Power source for the drivers was a 20,000 microfarad capacitor charged to 200 volts. The energy from both resonators is being fed into the single discharge.
     No great things have ever been discovered with my phase experiments. Perhaps the most significant observation was the fact that the resonant frquency of a multiple resonator system changes slightly between different modes, even though nothing physically was changing.