Editing Continuous wave (section)

===Transmissions before CW===
Very early radio transmitters used a [[spark gap]] to produce radio-frequency oscillations in the transmitting antenna. The signals produced by these [[spark-gap transmitter]]s consisted of strings of brief pulses of [[sinusoid]]al radio frequency oscillations which died out rapidly to zero, called [[damped wave]]s. The disadvantage of damped waves was that their energy was spread over an extremely wide band of [[Frequency|frequencies]]; they had wide [[bandwidth (signal processing)|bandwidth]].  As a result, they produced [[electromagnetic interference]] ([[radio frequency interference|RFI]]) that spread over the transmissions of stations at other frequencies.

This motivated efforts to produce radio frequency oscillations that decayed more slowly; had less damping. There is an inverse relation between the rate of decay (the [[time constant]]) of a damped wave and its bandwidth; the longer the damped waves take to decay toward zero, the narrower the frequency band the radio signal occupies, so the less it interferes with other transmissions. As more transmitters began crowding the radio spectrum, reducing the frequency spacing between transmissions, government regulations began to limit the maximum damping or "decrement" a radio transmitter could have. Manufacturers produced spark transmitters which generated long "ringing" waves with minimal damping.