Portable radios needlessly waste most of their batteries’ energy, according
to Duncan Grant of the University of Bristol. Although the amplifier needs a
3-volt power supply, the tuner needs only 1.5 volts. Feeding it 3 volts is
wasteful, but voltage converters are also inefficient and using a different
battery to power the tuner means the batteries go flat at different times.
Instead, Grant’s radio uses a digital amplifier (GB 2 314 474). Digital
amplifiers create rapid alternating pulses, and by skimming off half of these
pulses, Grant supplies the tuner with 1.5 volts. The batteries of a conventional
radio go flat in 200 hours—just 20 days at 10 hours a day. But with
Grant’s design, they work for 7400 hours—or over two years.
