Arc converter

One of the first transmitters that could generate continuous sinusoidal waves, it was one of the first technologies used to transmit sound (amplitude modulation) by radio.

[3] Elihu Thomson discovered that a carbon arc shunted with a series tuned circuit would "sing".

[5] The English engineer William Duddell discovered how to make a resonant circuit using a carbon arc lamp.

After a few years of development the arc technology was transferred to Germany and Great Britain in 1906 by Poulsen, his collaborator Peder Oluf Pedersen and their financial backers.

In 1922, the Bureau of Standards stated, "the arc is the most widely used transmitting apparatus for high-power, long-distance work.

It is estimated that the arc is now responsible for 80 per cent of all the energy actually radiated into space for radio purposes during a given time, leaving amateur stations out of consideration.

"[6] This new, more-refined method for generating continuous-wave radio signals was initially developed by Danish inventor Valdemar Poulsen.

The spark-gap transmitters in use at that time produced damped wave which wasted a large portion of their radiated power transmitting strong harmonics on multiple frequencies that filled the RF spectrum with interference.

Poulsen's arc converter produced undamped or continuous waves (CW) on a single frequency.

There are three types for an arc oscillator:[7] Continuous or ‘undamped’ waves (CW) were an important feature, since the use of damped waves from spark-gap transmitters resulted in lower transmitter efficiency and communications effectiveness, while polluting the RF spectrum with interference.

Sometime around 1921, the Preliminary International Communications Conference[11] prohibited the compensation wave method because it caused too much interference.

The back shunt was a second tuned circuit consisting of an inductor, a capacitor, and load resistor in series.