How Walkie-talkies Work


U.S. President George W. Bush speaks on a walkie-talkie during a tour of World Wide Technology, Inc. in 2008.
U.S. President George W. Bush speaks on a walkie-talkie during a tour of World Wide Technology, Inc. in 2008.
© MANDEL NGAN/AFP/Getty Images

Cell phone technology advances at a mind-warping rate. But cell phones are still just really fancy radios, and they have an Achilles heel -- they're completely helpless without a network of nearby cellular towers. Walkie-talkies, though? These old-school radios make short-range wireless communications possible in places where cell phones go to die.

Walkie-talkies are wireless, hand-held radios that are small enough to take just about anywhere. They look a lot like cordless phone handsets, with a body that includes a microphone and speaker, as well as an antenna. Unlike a phone, though, a walkie-talkie's speaker and microphone are placed right next to each other, and the speaker is much louder, so that anyone within earshot can follow the conversation.

Walkie-talkies are battery-powered transceivers, meaning they can both send and receive radio messages. They have a half-duplex channel, which indicates that only one walkie-talkie on a channel can transmit a signal at one time, although many radios can receive that same signal. In other words, unlike your phone, in which both parties can interrupt or add to the conversation in a ceaseless flow of sound, walkie-talkies use a push-to-talk (PTT) system -- you have to press a button in order to speak, and you have to release that button to hear sound coming from other units.

Because you don't have to dial a number each time you want to transmit, walkie-talkies are quick and easy to use. And best of all, they don't rely on finicky cell phone signals. The handsets transmit directly to each other, so they still work when cell networks fail during natural disasters or power outages. They're designed primarily for short-range communications, in which groups of people are within a few miles of each other.

Businesses use walkie-talkies so that employees can chat efficiently in and around their indoor and outdoor structures. Wilderness lovers tote walkie-talkies so that they can keep in touch during hiking or hunting trips out where cell phone cover age is non-existent. Even baby monitors employ one-way walkie-talkie technology, so that you know if Junior is sleeping peacefully or attempting escape.

Keep reading and you'll see how they developed and why they're such vital communication devices.

A Walkie's Inner Workings

All walkie-talkies feature the same basic components. Those include a speaker, microphone, battery, antenna, some circuitry and, of course, the iconic PTT button. These parts work in tandem to create useful radio signals.

Let's say you're whitewater rafting with a group of friends on a remote river, in an area where there's zero cell phone coverage. You depress the PTT button on your radio to chat with group members. As you speak, the walkie-talkie converts your voice into radio signals. Those signals are part of the electromagnetic spectrum, so they travel at the speed of light (186,000 miles, or 299,338 kilometers, per second) to all the other radios that are within range and on the same channel.

If you're not up to speed on radio technology basics, be sure to read How Radio Works. But in short, radios transmit and receive signals on any of millions of possible frequencies, which are denoted by units of Hertz (cycles per second). Those units are most often kilohertz (KHz) and megahertz (MHz). Modern, digital walkie-talkies may work on dozens of possible channels (or frequency bands), so in order to communicate with your buddies, you'll need to make sure you're all using the same channel before hitting the river.

All walkie-talkies are built to work on specific radio frequencies. In the United States, the primary frequencies designated for general public use are called Family Radio Service(FRS) and General Mobile Radio Service(GMRS). FRS or GMRS radios operate at frequencies in the 460-MHz range. The government also sets aside frequencies for corporate use, called Business Band, which includes frequencies between 450 and 470 MHz.

Frequencies are in finite supply, especially at the public level, so the airways are often jammed with too many signals at once, which can result in interference. As you'll soon read, many walkie-talkies come with features designed to filter out unwanted signals from other people. Still, radio signals often bounce around weirdly due to weather or other electromagnetic anomalies, which is why sometimes they pick up other signals inadvertently, such as in the West Virginia case of the baby monitor that spewed foul language from truckers talking on their CB radios [source: NBC News].

You'll learn more about how to filter signals later. For now, let's step back to the advent of walkie-talkies, and how they became so popular to begin with.

Wireless World War

Prime Minister Winston Churchill speaking on a walkie-talkie during a visit to Fort Jackson in June 1942.
Prime Minister Winston Churchill speaking on a walkie-talkie during a visit to Fort Jackson in June 1942.
© Bettmann/CORBIS

As with so many emerging technologies, it was warfare that helped propel walkie-talkies from prototype to mass adoption in a short time. During World War II, the U.S. and Allied forces were the first to put these newfangled radios into widespread use.

There were several groups working on this type of radio in the late 1930s, so it's impossible to attribute the exact genesis of the walkie-talkie to one person or company. Radio engineer Al Gross and Canadian inventor Donald Hings were on the forefront of this technological wave, as were research groups at Gavin Manufacturing Company, which is now better known as Motorola.

Just before 1940, Motorola produced a portable AM transceiver that became known as a handie talkie. This was an AM-based system (on frequencies from 3 to 6 MHz). It worked, but it was prone to degrading signal quality, meaning static and interference often made communication frustrating.

The first design to hit the battlefield in mass numbers, and the first to garner the walkie-talkie label, was the Motorola SCR-300. The SCR-300 was also an FM-based device (40 to 48 MHz), and much more resistant to interference than AM. It also had better range, at around 3 to 5 miles (4.8 to 8 kilometers).

FM-based radio signals offered the advantage of squelch, which just meant that the speaker went silent until an incoming signal arrived. Prior to squelch capabilities, radio operators who monitored AM signals had to endure long periods of mind- and ear-numbing static when no one was transmitting on the channel that they were monitoring.

The SCR-300 wasn't exactly as convenient as your average pocket-sized smartphone. It required a backpack that housed the battery, electronics and a 33-inch (84-centimeter) antenna, all of which totaled more than 30 pounds (13.6 kilograms). Try dodging Nazi bullets and bombs with that load on your back.

In spite of its heft, the unit was rugged and reliable in war zones, and tens of thousands of them were deployed to troops in both the Pacific and European theaters. The end result was forces that could communicate and coordinate their activities much more effectively than ever before.

After WWII, walkie-talkie technology hit the mainstream. Military versions got smaller, lighter and more powerful. Amateur radio lovers adopted walkie-talkies en masse. Consumer-grade versions appeared, too, with affordable price tags that made them perfect for basic communications around the house, in the field, and even as toys.

No matter what purpose you use them for, walkie-talkies all work pretty much the same. Keep reading to see how these wireless talking wonders conjure their magic.

What's the Frequency, Kenneth?

All walkie-talkies are made to work on specific frequencies that the government (in the U.S., the Federal Communications Commission or FCC) reserves for different types of transmissions. Police and firefighters, for instance, have their own frequencies so that business and public signals don't interfere with emergency communications. So you can go ahead and put down that fire hose and the badge you made from tin foil -- the authorities don't want you messing about on their channels.

As you already know, FRS and GMRS frequencies are made for public transmissions. The FRS and GMRS channels overlap at some frequencies, but the actual radios that access these channels have some distinctive differences.

FRS handsets come with fixed antennas and are limited to 0.5 watts, making them very low-powered devices that often only work at a range of a few hundred feet, so it's unlikely that your radio will ever interfere with a neighbor's a few blocks away. Those kinds of walkie-talkies are just personal-use devices, and anyone can transmit on FRS bands for any reason.

GMRS devices can be much more powerful, at up to 5 watts, or about the same power consumption of a smartphone that's using all of its primary features. What's more, GMRS systems can be used with repeaters, which are devices that boost the range of the radio signal. In either case, GMRS devices always feature better range than FRS-only handsets.

Keep in mind that there are plenty of hybrid FRS/GMRS radios available. These walkie-talkies let you transmit on both groups of channels. However, when you're transmitting on FRS, the handset's power automatically drops to 0.5 watts.

There's another critical difference between GMRS and FRS. Although anyone can use the FRS channels, only licensed radio operators are allowed to use GMRS frequencies.

That's because these radios are more powerful and more likely to cause interference with each other.

Licensing is simply a way to reduce congestion on GMRS channels. However, many people use GMRS radios and disregard license requirements because the FCC generally doesn't enforce these regulations.

FRS and GMRS are North American communications standards. In Europe, walkie-talkies mostly use PMR446, or frequencies at around 440 MHz. You can't use a PM446 radio to work on FRS or GMRS, or vice versa. It would be illegal to even try. So when you're traveling abroad, it doesn't hurt to verify that your radios operate on a legal frequency. In extreme circumstances, transmitting illegally on the wrong channels can result in fines or even jail time.

Real-world Radios

The basic components in kids’ walkie-talkies are the same as the ones grown-ups use.
The basic components in kids’ walkie-talkies are the same as the ones grown-ups use.
© Sean Justice/Corbis

With all this talk about frequencies and wattage, you might be wondering about the real-world range of walkie-talkies. Commercial-grade walkie-talkies have enough oomph to give them a range of several miles in ideal conditions. But as with so many product specifications, manufacturers often wildly exaggerate the range of their walkie-talkies, sometimes claiming that they'll work at more than 20 miles (32 kilometers).

But in areas where there are buildings, hills, trees or any sort of obstructions at all, expect the working range to drop in a hurry. In very congested areas, even good-quality radios may max out their range in several hundred feet.

Once you're within range of another handset, there's still the matter of conducting a proper walkie-talkie conversation. Because only one person can speak at a time, each walkie-talkie operator needs to know the rules. For example, saying "over" indicates that you are done speaking and that you're awaiting a reply. Alternately, by saying "over and out," you're telling listeners that you're done with your transmission and that the conversation is over. These so-called voice procedures are necessary to prevent people from talking over each other during transmission.

As walkie-talkie features become more advanced, some of these linguistic acrobatics are becoming less necessary. For instance, some radios send a beep tone when you release the PTT button, in effect replacing "over" with an automatic tone.

Radio lexicon can be a strange language for radio novices. But what's even weirder? The sound of a stranger's voice on your handset.

If another person's radio is within range of yours and it happens to be set to the same channel, there's a chance that you'll hear what he or she is saying, and vice versa. To prevent this, your group can select a different channel, or you can invest in walkie-talkies with CTCSS (continuous tone-coded squelch system) or DCS (digital-coded squelch) encoding.

This encoding isn't encryption at all -- that kind of functionality is found only in military-grade radios. Instead, the encoding is just a type of filtering. In other words, your radio's speaker will only activate when it receives a transmission from another radio that precedes its message with a specific tone combination. Your group's radios, of course, must all be using the same privacy code in order to work with each other.

Even with privacy codes in place, walkie-talkie conversations are anything but secure. Think of these transmissions as publicly-accessible phone calls. Spewing weird rants or private details over the air violates basic radio etiquette and might garner some really unwanted attention from aggravated users.

Walking the Talkie

As sophisticated smartphones continue to proliferate, it's easy to see why some people would think of walkie-talkies as outdated technologies. That's especially true when you consider that many smartphone apps now simulate walkie-talkie PTT capabilities.

But even with said apps, cell phones are nothing like walkie-talkies. Cell phones will always be dependent on cellular towers, and even with those apps, they don't provide the instantaneous communication of a walkie-talkie. For outdoors lovers or anyone else who strays out of range of cell phone networks, there's no substitute for these handheld radios.

What's more, walkie-talkie manufacturers are constantly improving their products and even tying them to the popularity of smartphones. Cobra Electronics, for instance, makes a Bluetooth-enabled handset that works through your cell phone to make and receive calls. So while you're plummeting through rapids, your phone can remain stowed safely away while you call out on your walkie-talkie.

Cobra also equips some models with a rewind button. So if you miss part of a transmission, you can push the button to hear up to 20 seconds of audio, which means you won't have to ask the sender to repeat the message.

Power and sensitivity continue to increase, and prices continue to go down. And if you're willing to spend more? You'll get bigger handsets with a lot more manual controls, and -- just as important -- larger batteries that last longer between charges.

More and more walkie-talkies also come with ruggedized components so that they'll withstand the abuse of the outdoors. Many are water-resistant and some even float. And many models now come with voice activation (VOX) so that you don't even have to press a button to begin speaking.

All of these advances speak to the continuing relevance and usefulness of walkie-talkies. For a decades-old radio technology, that's serious longevity, especially in the face of so many new communications devices. For now, walkie-talkies and their radio-based brethren are here to stay. Over ... and out.

Author's Note: How Walkie-Talkies Work

I had a pair of Spider-man walkie-talkies when I was kid. We used to run around the yard with them, pretending we were coordinating epic battles happening right there in the dandelions. Usually, though, those games ended abruptly because we couldn't hear each other speaking over the ever-present static. These days, walkie-talkies are so much more sensitive and powerful that with a good-quality pair (and of course, the proper GMRS license) you'll be able to execute tactical maneuvers from miles away. They just won't have the cool Spider-man logo on them.

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