Microwaves Everywhere

Peter Gibson – 14th February 2006

The so-called Peace Dividend from the once secret military uses of microwave energy was amply illustrated in the first third of this talk by way of a PowerPoint slide show (courtesy of Ken Wheller). They range from the esoteric command, control, and communications at 3,000 million miles for the New Horizons space probe to Pluto to the mundane mobile phone in your pocket, and from the domestic microwave oven to traffic light control at country road works; taking in EGN (electronic news gathering) and medical LINACS (linear accelerators) along the way.

The second third of the talk was taken up with the properties of microwave radiation. Holding up a pocket radio in the left hand and a torch in the right he explained that microwaves and the infrared shared the territory in between. Current everyday uses for microwaves (TV, satnav, rfid tags, etc.) are all crammed into the 1,000 to 12,000 MHz atmospheric window which also, alas, includes the astronomers’ 21cm neutral hydrogen line which he illustrated as an aside with slides of the constellation Cassiopeia in both the visible and the microwave spectrum.

The third part of the talk dealt with the engineering breakthroughs that led to the release of these radiations, for good or ill, on domestic populations all over the world. Holding up his (still painted yellow) spanner the speaker recalled that microwave engineers are called plumbers in the USA because of their propensity for erecting long runs of ‘waveguide’ from masthead to radar cabin, down mast and through cabin walls without so much as a ‘say so’. The breakthroughs came with the almost simultaneous development of digital radio, the discovery of the Gunn diode effect, thin film printed circuit technology, very inexpensive and reliable methods of producing substrates, and beam-lead diode technologies. The use of a doughnut and pencil was left to the end of the talk.

Peter Gibson