Neon Bulb Oscillators

Neon Tube Oscillators 

Fig. 1 High voltage to headphones, don't do this in modern times. Very high impedance headphones are implied.

A neon bulb is useful in many ways in an amateur station, but there are undoubtedly many amateurs who are not aware of the fact that the device can be made to oscillate at either audio or radio frequencies.

Fig. 1 shows how a single bulb may be hooked up as an audio frequency oscillator. The L-C circuit is formed by the headphones and a condenser, and by varying the capacity the circuit can be made to oscillate at frequencies from a few cycles per second up to the highest audio frequencies. 

The variable resistor in series with the bulb and battery controls the strength of oscillation, and also controls the frequency to some extent. A 1 nf variable condenser will be sufficient to cover most of the audio range. 

Fig. 2

The circuit in Fig. 2 may be used when an RF oscillator is to be modulated at audio frequencies. The transformer may be an ordinary audio transformer, the primary being connected to the RF oscillator circuit.

Fig 3.

The push pull circuit in Fig. 3  for operating at radio frequencies. With the constants given in the diagram the oscillator will work over the broadcast band. The 1/2 watt sized neon bulbs are used. In getting the oscillator started the series resistance in the circuit should be slowly increased until the bulbs just start to glow. Too much current will cause he oscillations to stop. It is possible that the audio and radio oscillators could be combined to make a modulated oscillator for the broadcast band. The advantage of such a set is that no expensive tubes are required and no filament power needed.