Short Wave Therapy

Ref. M5

“Shortwave” refers to electromagnetic radiation in the frequency range 2 to 100 MHz. Short wave therapy is the application of electromagnetic energy to the body at shortwave frequencies. At these frequencies the electromagnetic energy is converted to thermal energy by the induction of tissular reactions. Shortwave therapy units may produce output power levels of up to 500 W providing significant heating to the area of the body being treated. For this reason the treatment is often called shortwave diathermy (i.e. through heating). To avoid shortwave therapy units interfering with radio communications, certain frequency ranges are designated by international agreement as ISM (Industrial, Scientific and Medical) bands.

These short waves are unmodulated radio waves, produced in a special machine containing an oscillator circuit. The heart of of this circuit used to be a heavy duty triode valve, presently replaced by a “solid state” design. The radio-frequency waves produced are applied to the patient’s body by special applicators. The frequency of the waves could be controlled by a variable condenser. (From the Internet)

The pictures below are show two huge triode valves, respectively made by Siemens and by Philips, used in the oscillator circuits of old short wave therapy machines and dating probably to the forties of last century.