The clock on an inexpensive radio in my bedroom ran so fast that I had to reset it at least monthly. In the end, I moved it to a less-used spare bedroom and bought a replacement. The first one now seems to keep time just as well as the new clock. Why? How?
Thanks to Jeremy Greenway of Bacup, Lancashire, UK, for his suggestion that we should have looked across the page to Feedback for the answer to this. He wonders if our correspondent has recently 鈥渂ought a set of Pyramidal Memories Transmutation tubes, or something similar, to fully hydrate your waters and optimise your tachyonic flow?鈥� Nice try Jeremy, but no cigar 鈥� Ed
鈥� Cheap clock radios plugged into the mains electricity supply tend to count the number of cycles in the supply and use this to keep time. However, any interference to these cycles or to the clock can make them speed up. In our bedroom we have two identical clock radios. The one on my side of the bed gains 20 minutes a month, the other doesn鈥檛. If we swap them, the one on my side still gains and the other doesn鈥檛.
Advertisement
鈥淎ny interference to the mains-electricity supply cycles can make a cheap clock radio speed up鈥�
The reason for this is that my side is less than a metre from a dimmer switch that produces enough electrical noise to cause a problem. I鈥檇 hazard a guess that your correspondent has a dimmer switch near the radio in the bedroom but not the spare room. If there is no dimmer or other obvious source of noise, such as an automatic tea-maker, you should get the wiring checked.
Tom Potts, Holsworthy Beacon, Devon, UK
鈥� If it has a digital display, the aberrant clock probably uses the as its timing reference, detecting the number of times the sine wave of the frequency passes through zero volts. It may be connected to a supply that has something else on the same branch circuit, which introduces an electrical disturbance that generates multiple extra 鈥渮ero crossings鈥�, causing the clock to run fast.
If the clock has an analogue display, the cause may be similar but the electrical disturbance distorts the sine wave, causing harmonic frequencies that confuse the motor. The supply to the spare room is probably on a separate branch that suffers no disturbance. The new clock either has better immunity to disturbance or uses a crystal oscillator for its timing reference, independent of the mains supply.
John Woodgate, Rayleigh, Essex, UK
鈥� This question came from Australia, a country with a hot climate. It is possible that one room is air-conditioned, but the air-conditioning is switched off in the spare room, so it鈥檚 hotter there. Battery-powered clock radios are regulated by vibrating quartz crystals. These expand and contract depending on the temperature and can cause clocks to run faster or slower.
Ralph Hancock, London, UK