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Condenser and a Van De Graaff (Spark Gap Transmitter).

Joe Labs

A primitive transmitter with primitive parts.!

I gave myself the challenge of building a most simple form of transmitter. Needling no or very little input power to possibly work the world on the Ham Radio HF bands.
For the sake of science and experimentation. Not to be used in real world on an external antenna today of course, As these Spark type of radio transmitters have been
banned world wide long ago because the simplicity comes at a cost. This type of circuit produces wide band harmonics across the radio spectrum. How ever. As far as
getting the job done as of being a simple fail safe method of communicating world wide. The spark transmitter does indeed get the job done. No Tubes and no
Transistor. Not even a tunnel diode. This is a very interesting method of moving radio frequency energy into the air.

Here is the typical circuit diagram of a simple spark gap transmitter.
Looking at this. It is simple to observe that all I really need is
a source of high voltage and a spark gap (interruption) setup. When you do this in a Tesla like system. Adding an external antenna will cause the RF to radiate away.

Following the circuit diagram. We now have a very crude high voltage CW wireless transmitter.

I reasoned that I could build a very simple high voltage generator to drive the transmitter stage with. First and most simple method that came to mind was an electrostatic
generator. So I moved on to build one with parts I had laying around the house.

Parts For Electrostatic Generator

-Elastic as rubber band.
-Stainless water bottle for top capacitor.
-Plastic toy frame as holder and insulation.
-Copper wick.
-1.5 volt toy DC motor to spin rubber band.
-Two 1.5 volt AA batteries to operate belt motor.

Here is the basic inner workings of the Van De Graaff.
Van De Graaff A rather simple process to replicate.

The interesting aspect of this kind of transmitter is. The RF is not being produced by the energy stored in the AA battery. Those batteries are simply to spin the belt. Inside the
 Van De Graaff. This produces an electrostatic charge potential.  We are able to charge high voltage condensers and short them out like any other regular high voltage experiment.
I was able to use this as my high voltage source. Able to produce a spark gap within a Tuned L/C circuit. This is very much like a "Tesla" coil. With the addition of a radiating
antenna. The L/C circuit oscillates and radiates radio frequency just fine with "electrostatic" And can in theory communicate with the world on Ham radio HF bands.


                   Van De Graaff

                              All I have to do is feed this spark gap HV into the radio L/C circuit, Such as the one seen in the circuit diagram I provided on the top of this page.

Moving on:

I wanted to build a better version. I wanted to use the same two AA batteries. But with a different method. This Time I wanted to drive the high
voltage with a tiny flyback oscillator. The most basic joule thief one transistor free running circuit. such as the one seen in the photo below.

I built a small high voltage version of this. By replacing the transformer
with some high voltage flyback high frequency transformers I found on ebay. It saved me the time to wind all those high inductance with tiny wire
in a place that is not really setup as a shop. My home.

Have you ever had one of those Radio Shack 150 in one electronic kits or similar? I decided to use the internal parts of this kit as part of my
transmitter. Since the all in one kit has an AM "loopstick" antenna and L/C circuits. It was easy for me to direct the high voltage spark gap
oscillations into this kit and use the internal parts to tune all around the AM and Shortwave bands!


What your looking at is the spark gap
in the front of the unit.


        High Voltage

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