The end of the vacuum tube era... If you're not an electronics geek, you can be forgiven for believing vacuum tubes disappeared quite a few years ago, with the advent of flat screen TVs. In fact, millions of vacuum tubes are still being manufactured every year, and bought by consumers worldwide – including, quite likely, you. Every microwave oven manufactured since the 1940s contains a vacuum tube called a cavity magnetron – the gadget that produces hundreds of watts of microwave radiation to heat your food.
I've long been fascinated by cavity magnetrons, less for their technical attributes than for their contribution to the Allies victory in WWII. Their invention by British scientists, and mass production by American industry, led directly to small, lightweight, high resolution airborne radars – and gave the Allied air forces a huge advantage over those of the Axis. That same device is what cooks your food in today's microwave ovens.
But this is about to change. As this article describes, recently introduced high frequency, high power transistors are about to revolutionize the world of the microwave oven. The transistors are better in many ways, but what the consumer will notice is infinitely variable power, and no loud noise.
My electronic career got started with devices that used vacuum tubes as their active components. It's been many years since I last designed something using a vacuum tube, but I've still got a fond place in my engineer's brain for them. Once the microwave industry has converted (which I expect will happen extremely quickly), there will be no more high volume vacuum tube production – just low volume boutique production for the crazy people (some of my friends amongst them :) who think vacuum tube audio amplifiers sound better than solid state ones...