People occasionally post here examples of the 'violet wand' radio-frequency therapeutic devices they've acquired. Most of these are really nothing more than showy placeboes.
At a car-boot-sale a while back I bought a book - see frontispiece - which though generally aimed at the commercial short-wave communications world [lots of talk of multiple-diversity receivers, directional antenna-arrays occupying a few tens of acres, and frequency-compensation at the interface between telephone-lines and short-wave transcontinental relays] it has an intriguing section on 'proper' medical RF-devices as were current in the mid-1940s.
These meant business: the descriptions include
"a model employing two water-cooled valves operating over a wave range from 2 to 8 metres, giving an H.F. output from 1.8kW at 2.5 metres up to 3.4kW on wavelengths of 6 metres and above".
"It is designed to give an output of 300 Watts at a fixed wavelength of 6 metres (50 megacycles)"
"This set operates on a wavelebgth of 6 metres (50 megacycles) and fives an output of 450 Watts".
The circuits shown all use self-excited power-oscillators with raw AC on the valve anodes. The RFI/TVI potential of these things must have been truly horriffic, being coupled to the patient [I'd prefer the term 'victim'] by unscreened wires.
I guess they got away with it because they'd generally be using these things during the day and at the time there was no daytime TV!
Anyone else got examples of these sorts of things??
Of course, in the early stages of WWII, similar diathermy-machines working around 27-30MHz were repurposed by Air Vice Marshal Edward Addison and '100 Group' as noise-generators to jam the german 'Knickebein' blind-bombing beams.... so perhaps medical-RFI had an excuse...
https://en.wikipedia.org/wiki/Edward...e_of_the_Beams