Radio controlled clocks
A radio controlled clock corrects itself continuously against an atomic reference instead of drifting the way an ordinary quartz movement does. Most of the clocks here receive the MSF signal broadcast from Anthorn in Cumbria; some, including several German-made models, receive the DCF77 signal from Mainflingen near Frankfurt instead. Either way the clock is accurate to the second, and it moves itself forward in March and back in October without you touching it.
One thing worth knowing before you buy: a DCF77 clock arrives set to Central European Time, so in the UK you enter a time zone offset of minus one hour once during setup and then leave it alone. There is more on this below.
The range covers wall clocks, bedside alarm clocks and weather clocks with wireless outdoor sensors. For clocks of every type see the full clock range, or wall clocks and weather clocks for those categories specifically.
How radio controlled clocks work
A radio controlled clock contains a small long-wave receiver. Once or several times a day it listens for a time broadcast transmitted from a national standards laboratory, decodes the time and date from it, and corrects its own timekeeping to match. Between updates it runs as an ordinary quartz clock, so a missed update overnight changes nothing you would notice.
The practical consequences are the ones that matter. The clock is accurate to the second rather than to the minute or two a quartz movement drifts to over a year. It handles the seasonal clock change on its own. And it needs no setting beyond inserting batteries — no hour buttons, no seconds to line up.
These clocks are often sold as atomic clocks. Strictly they are not: the atomic clock is at the standards laboratory, and yours is a receiver. The accuracy you get, though, is genuinely atomic-referenced.
MSF or DCF77, and the UK time offset
Two long-wave time signals cover the United Kingdom, and which one your clock uses determines whether you need to do anything at setup.
MSF is transmitted from Anthorn in Cumbria on 60 kHz, carrying time and date derived from the atomic clocks at the National Physical Laboratory. It broadcasts UK time, so an MSF clock shows the right time straight out of the box and switches between GMT and British Summer Time by itself. Nothing to set.
DCF77 is transmitted from Mainflingen, near Frankfurt, on 77.5 kHz by the German national standards institute. It reaches the UK perfectly well, and many European-made clocks use it. But it carries Central European Time, which is one hour ahead of us. A DCF77 clock will therefore show 4pm when it is 3pm in Britain until you tell it otherwise.
The fix takes seconds. Every DCF77 clock sold for the UK has a time zone or offset setting — usually marked ZONE, TZ or OFFSET — which you set to −1. The clock then applies that offset to every signal it receives from then on. You do it once and never again.
The offset also stays correct all year, which surprises people. Central European Summer Time begins and ends on the same Sunday as British Summer Time, so both zones shift together and the one-hour gap between them never changes. There is no need to adjust the offset in spring or autumn.
Among the clocks here, the Bresser Jumbo LCD wall clock in black and the white version are DCF77 models, so set them to −1 when you first fit the batteries. If you are unsure which signal a particular clock uses, the manual will say, or call 01243 558280 and we will check it for you.
Wall clocks that set themselves
This is where radio control earns its keep most obviously, because a wall clock is the one you least want to take down. The Yarnton radio controlled wall clock is the traditional analogue option, with a conventional face and hands driven by a radio-corrected movement.
For a large digital display, the Bresser Jumbo LCD wall clock in black and the white version combine radio controlled accuracy with day and date on a screen readable across a room. Both suit a kitchen, office or workshop where the time needs to be right and visible, and both are DCF77 models needing the −1 offset described above.
Alarm clocks
A radio controlled alarm clock removes the one real risk of a bedside clock, which is that it has quietly drifted or that you forgot the clocks changed. The Technoline WT486 dual alarm clock with FM radio offers two independent alarms, useful where two people in the same room get up at different times, plus an FM radio.
The Technoline WT549 projection alarm clock takes it further by projecting the time onto the ceiling, alongside indoor and outdoor temperature and a weather forecast. See projection clocks for more on that format.
Radio controlled weather clocks
Several models combine radio controlled timekeeping with a wireless outdoor temperature sensor, which is a genuinely useful pairing: the time is always right and the outside temperature is always current.
The Technoline WS 9767 gives you indoor and outdoor temperature with an alarm clock, and the WS9140 presents the same information in a clock-led layout. For fuller forecast displays with barometric pressure and humidity, see the weather clock range and home weather stations.
Reception, and what to do if it fails
Both signals cover the whole of the UK comfortably, but they are low-frequency and they can be blocked locally. The usual culprits are thick stone or concrete walls, steel-framed and steel-clad buildings, basements, and proximity to electrical noise — a router, a television, a monitor, an LED driver or a fridge motor.
If a new clock has not synchronised, three steps solve almost every case. Give it a full night: reception is best between midnight and six, when atmospheric conditions favour long-wave propagation and household electrical noise drops away. Move it temporarily to a windowsill facing the transmitter — north-west towards Cumbria for an MSF clock, south-east towards Germany for a DCF77 one — let it sync there, then return it to position. And keep it at least a metre from anything electronic.
One more check worth making before assuming a fault: if the clock has synchronised but reads exactly one hour out, it is a DCF77 model receiving perfectly well and simply needs the time zone offset set to −1. That accounts for most of the calls we take about radio clocks showing the wrong time.
If it still will not receive, the clock is not faulty — it will keep time as an accurate quartz clock and simply needs manual setting twice a year. Every clock here supports manual setting as a fallback.
Batteries
Radio reception draws a little more power than plain timekeeping, so a radio controlled clock will not run quite as long on a set of batteries as a basic quartz movement. Use good-quality alkaline cells indoors, and lithium cells in any outdoor sensor, which is where cold weather causes most dropouts. A weak battery in the outdoor sensor is by far the most common reason an outdoor temperature reading disappears in midwinter.
Related ranges
See wall clocks for indoor and outdoor wall models, weather clocks for forecast displays, projection clocks for ceiling projection, and the full clock range for everything else. For clocks with full weather measurement including rainfall and wind, see home weather stations.