Clocks That May Be Operated Through Radio Or Atomic Power

Even if you’ve got the most expensive watch in the world, it’s of little use to you if it’s set to the wrong time. Despite the fact that quartz clocks have an incredible 99.998% accuracy, even the best of them have a hard time keeping time to within a second a day; if they drift off by only a few seconds in 24 hours and the inaccuracies don’t cancel out, that could mount up to over a quarter of an hour a year. As a result, the vast majority of people make it a habit to double-check their watches against a recognized time signal, such as the one heard before radio newscasts. You know, if your watch could listen to such broadcasts and automatically adjust the time, wouldn’t that be great?! Radio-controlled clocks and watches, which use ultra-accurate atomic clocks to determine their time, work on this principle. Now that we know what they are and how they operate, let’s take a closer look!

Radio-synchronized watches and clocks make it possible for everyone to possess a timepiece as precise as an atomic clock. It was in the 1980s and early 1990s that radio-controlled clocks and watches began to gain popularity, thanks to businesses like Junghans. There are now a wide variety of manufacturers producing them, and they are in use across the world.

What is an RCC?

When you use a clock or watch to keep track of the passage of time, you’re accumulating seconds, minutes, hours, and days. In reality, the clock doesn’t know the time unless you set the clock to the correct time in the first place: it isn’t a time-keeping device. There are advantages to using a radio-controlled clock (RCC). An antenna receives up radio signals, and a circuit decodes them, making it identical to a regular electronic clock or watch. Using radio signals, the circuit tries to figure out what time it is and then updates the time on the clock or watch to match that result. Unlike a regular clock or watch, an RCC is always aware of the current time.

What is RCC?

Ordinary time-counting devices such as a clock or watch are used to record the passages of time. Unless you tell it, it doesn’t know the time unless you set it to the correct time in the first place. There are advantages to using a radio-controlled clock (RCC). An antenna receives up radio signals and a circuit decodes them, making it similar to a standard electronic clock or watch. Using radio signals, the circuit tries to figure out what time it is and then updates the time on the clock or watch to match that result. Unlike a regular clock or watch, an RCC is always aware of the current time.

Do you know what atomic clocks are?

Quartz clocks, like the ones you use every day, are the basis for atomic clocks. Unlike a normal quartz clock, a digital clock uses a combination of the movement of the clock’s hands and the movement of its crystal to count seconds. We’ve previously established that factors like temperature influence the rate at which quartz vibrates, so even while quartz clocks are normally quite accurate, they may not provide the level of timekeeping you want. As opposed to a conventional quartz clock, an atomic clock employs pulsing atoms as an additional mechanism to preserve accurate time.
The accuracy of quartz clocks like this one served as “time standards” for other timepieces until atomic clocks were invented. In the United States, this 1941 Quartz Crystal Time Standard was utilized until 1949, especially during World War II to coordinate military troops all across the world. Photos by National Institute of Standards and Technology, Gaithersburg, MD 20899, Digital Collections.

Atomic clocks made out of cesium

Electrons in certain energy levels are thought to exist in atoms, and this process is predicated on this. To put it simply, electrons are unstable when an atom absorbs energy. Returning to their original or ground state, they release the same amount of energy as photons of light (or other electromagnetic radiation, such as X-rays and radio waves). In many atomic clocks, the cesium atoms are utilized because of the atom’s 55 electrons, which are organized into orbitals. The outermost electron has the ability to fluctuate between two different levels of energy by spinning in two slightly different directions. It emits a photon with a frequency of precisely 9,192,631,770 Hz when it transitions from the higher to the lower of these states (roughly 9.2 billion hertz or 9.2 gigahertz). That means that the same microwaves may be used to stimulate it from a lower state to a higher one. This interesting characteristic may be used to maintain a very accurate quartz clock.

The NIST-F1 Cesium fountain atomic clock, which is used to set nearly every other clock and watch in the United States, may be seen in this photo. According to the NIST Physics Laboratory, this image was provided by them.

There is a quartz oscillator tuned to 9,192,631,770 Hz in a cesium atomic clock that generates microwaves and launches them towards a group of cesium nuclei. In this case, assuming the microwave frequency is proper and hasn’t wandered at all, these microwaves will have just the required amount of energy to move the atoms’ electrons to their higher energy states. The clock’s magnetic detector counts the atoms at various energy levels. In order for the majority to be in a higher condition, the quartz oscillator must have aroused them. So the quartz oscillator must be keeping accurate time if those waves have the correct frequency. It’s possible that an oscillator has strayed away from its correct frequency and isn’t sending out the necessary amount of energy to encourage electrons in the cesium atoms if the majority of the atoms are in the lower state. Detecting this, the clock’s feedback mechanism changes the oscillator frequency so it’s once again accurate. As a result, the quartz oscillator is regularly controlled to ensure that it is always set at 9,192,631,770 Hz. With this precise frequency, an electrical circuit may be utilized to control a quartz clock mechanism with incredible precision. A second in 1.4 million years, or 2 nanoseconds every day, is an incredible amount of precision for an atomic clock.

Atomic clocks of a different kind exist.

Different gases are used to govern the quartz oscillator in other atomic clocks in a similar manner. A microwave-frequency laser (maser) stimulates hydrogen atoms in a hydrogen clock, however, this is less practical due to hydrogen’s difficulty in containment. Simpler rubidium clocks employ microwaves to activate the atoms in rubidium glass, making them smaller and more portable than their more complex and bulkier counterparts. Some of the most modern timekeeping devices on Earth employ what is known as an “atomic fountain,” a type of atomic clock. Lasers hold cesium atoms, cool them to near-absolute zero, bounce them upward, and then let them fall back down by gravitational forces (hence the name “atomic fountain”). This causes them to bounce between two exact energy levels that may be measured, in a manner similar to how a quartz clock maintains its accuracy.

Is it possible to explain the workings of an atomic clock?

A lump of cesium metal is heated in a red oven until the cesium atoms begin to boil out of it at one end of the clock. Both unexcited and excited states are possible for the atoms (yellow).

One end of the oven is equipped with a magnetic filter that only enables orange atoms to pass through.

A microwave cavity is where the unstimulated atoms enter. A quartz oscillator (green, 6) generates microwaves that are theoretically adjusted to a magical frequency of 9,192,631,770 Hz.

Most of the cesium atoms will be excited if the quartz oscillator is set to this frequency precisely. Otherwise, only a tiny minority will be enthused. The energized atoms are allowed to pass via a second magnetic filter.

A detector counts the number of atoms that have been stimulated.

The microwave oscillator (green) receives a signal from the detector, which it uses to alter its frequency in order to excite as many atoms as possible. This guarantees that the oscillator’s frequency remains as near to 9,192,631,770 Hz as feasible.

This high-frequency signal is lowered in frequency by an electronic divider circuit (blue) so that it may be used to power a standard quartz clock mechanism.

The accurate atomic time is displayed on a digital display (gray) attached to the circuit.

Radio-controlled clocks were created by whom?

“There is no clear consensus on who created the first RCC that could synchronize to a wireless signal,” states NIST’s Michael Lombardi, a world authority on radio-controlled clocks. Frank Hope-Jones (1887–1950) created the Horophone, which was offered by his Synchronome Company of London, England, beginning in 1913.

Using the US Patent and Trademark Office database, I learned that the first RCC patent was submitted by Thaddeus Casner for the Radio Electric Clock Corporation of New York City on March 24, 1921 (granted on February 5, 1925). His innovation includes “… a device by way of which a clock may be regularly adjusted by electrical impulses conveyed over space… [by] Hertzian waves (what we now call radio waves]…” Casner says. If you’d want to learn more about this invention, you can check out US Patent: #1,575,096: Mechanism for Synchronizing Clocks (via Google Patents).

Artwork: A sketch of the first radio-controlled clock by Thaddeus Casner. While the typical gear mechanism (blue) is used to keep time, radio signals drive electromagnets (red) to ensure the accuracy of the device. The US Patent and Trademark Office provided the artwork for this piece.

Does it really make sense for clocks to be so precise?

We are now able to tell the time within a millisecond or two every single day. That may sound like a great idea, but it’s actually simply a trade-off. When it came to timekeeping in the past, the difficulty was that we couldn’t keep up with “natural precision” in actual life. Consequently, human clocks were unable to keep up with the natural timekeepers in the sky, despite the planets and the heavens turning.

Ironically, the situation has now flipped. Instead of using the movement of planets when defining the passage of time, we now focus on the atomic oscillations. Cesium-133 oscillations between two energy levels have defined the second since 1967. (for reasons we saw up above). You’ll see that the planets and stars eventually drift out of sync if you use an atomic clock, as many national standards agencies throughout the world now do. For example, the Earth’s rotating speed fluctuates, with sporadic blips and a progressive deceleration. As a result of all this, we must “correct” our atomic clocks from time to time to keep them in sync with the world around them. Adding “leap seconds” to the official, scientifically measured global time (International Atomic Time, TAI) ensures that it always matches the official time that people use (Coordinated Universal Time, UTC).

History of atomic time in a few sentences

U.S. Dunmore Bureau of Standards developed this radio-controlled clock synchronization system in the early 1980s. The Library of Congress has provided a copy of Harris & Ewing’s photograph.

• Around the year 1879, British physicist Lord Kelvin (William Thomson) proposed using sodium and hydrogen atom energy transitions to tell the time.
• Isidor Rabi, an American scientist, developed the atomic beam magnetic resonance (ABMR) technology in 1937, which employs magnetism to evaluate the characteristics of an atom. For his efforts, he is awarded the 1944 Nobel Prize in Physical Sciences.
• 1945: Rabi proposes a design for a workable atomic clock.
• ABMR approach developed by Rabi’s student and partner Norman Ramsey leads to the construction of the cesium atomic clock in 1949. The Nobel Prize in Physics is later awarded to Ramsey for this discovery.
• It was in 1949 that the US National Bureau of Standards (officially known as the National Institute of Standards and Technology (NIST) in 1988) constructed what is now known as the world’s first atomic clock using ammonia gas and a maser (microwave laser). Even though it was far from perfect, it served as proof that atomic clocks can be constructed.
• The NBS-1 cesium atomic clock prototype is built in 1952, but further development is halted due to political issues.
• Louis Essen and Jack Parry begin work on atomic timekeeping in the UK at the National Physical Laboratory (the UK counterpart of NBS/NIST). 1953.
• Cesium-1, the world’s first ultra-reliable cesium atomic clock, is built by Essen and Parry in 1955.
• The first commercial atomic clock, the Atomichron, went on sale in 1956 or 1958.
• 1959: Cesium-2, the improved clock from Essen and Parry, with a timekeeping precision of one second in a thousand years.
• To reflect this new definition, the SI was updated in 1967 to read “the length of 9,192,631,770 cycles of radiation,” or “the transition between two hyperfine levels of ground state” of the cesium-133 atom. As a result of this shift in human history, time is no longer measured according to the movement of the planets and stars.
• It was built in 1993 by the National Institutes of Standards and Technology (NIST) as a cesium beam atomic clock that was used in the United States until 1999.
• In 1999, NIST develops NIST-F1, a ten-times-more-accurate successor to NIST-7. It has an accuracy of one second in 100 million years because to the use of cesium fountain technology.