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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
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