Two-way Radios: How Do They Work?

In simplest terms, two-way radios convert your speech into radio waves and transmit them through the air. When those radio waves are picked up by another radio, they are converted back into audio. A two-way radio system can be as simple as two radios connecting directly to each other, or as complex as a network that covers an extended area. 

Because this type of communication relies upon radio frequencies, when individuals desire to talk to each other, their devices must be tuned to the same frequency (or channel). The term radio frequency means the number of oscillations in that radio wave, the electromagnetic forces that contribute to radio communication. A tuner is also included in each two-way unit to allow the sorting of different frequency signals, allowing the user to send and receive messages from a particular frequency.  

Like how two people need to be in the same room to talk, two-way radios rely on specific frequencies, or "channels," to communicate. These channels act as a unique wavelength that allows the devices to both send and receive messages. The built-in tuner that helps it find and understand the right signal, much like how a car radio finds a particular station to play music. 

This conversion of radio waves can be transmitted as either an analog or a digital signal. With modern digital radio, it is possible to also send other types of data over the radio waves—such as text messages, status updates, or other applications. With digital radio, it is even possible to encrypt data, helping to prevent third parties from intercepting your communications or using your network without your permission. 

Transmission Considerations 

Transmission power is measured by wattage, and the FCC (Federal Communications Commission) has regulatory limits on the wattage of both FRS and LMR frequencies. Some channels have low power requirements (typically 0.5W) and many FRS frequencies are limited to a maximum output power of 2 watts. Most LMR channels have a 5W limit (handheld), and repeater channels and mobile units have a 50W power limit.  

The transmission power of handhelds is also limited by other factors such as battery life and radio frequency exposure restrictions. More battery is used to transmit at a higher power, so demanding users will require a handheld with the battery capacity to communicate longer on high power settings, in addition to a simple and easy battery charging option like a dock or a generic USB cable. 

Line of Sight and Obstructions 

Without a repeater, a two-way radio’s range is determined by a clear and unobstructed line of sight. With a direct line of sight, you can be sure your range will be the best it can be given your transmission wattage. For areas without terrain obstructions, the curvature of the earth can even impact line of sight. In certain cases, transmission between two different altitudes can also improve range. 

The radio’s line of sight can be inhibited by any solid object: topography, vehicles, foliage, and even buildings. Using an exterior antenna when transmitting from your optimizes range since your own vehicle can act as an obstruction to your line-of-sight.  

Repeaters  

A repeater acts as a relay, and effectively “bounces” a signal between two-way   radios. Because it acts as a relay, it can be used to dramatically improve two-way radio range.  

Since two-way radio operation relies on direct line of sight, the addition of a repeater increases the area of coverage, since they amplify and re-broadcast the signal. This can be particularly useful when a repeater is placed at elevation (on top of a tower, building, or peak) because line of sight is maximized for both the transmission and receiving ends.  

This means that if repeater-capable two-way radios are within range of a repeater but not each other, they can still communicate with one another. This effectively enhances radio coverage, even in remote locations with environmental obstructions or large altitude variations. Strategically placed repeater units can extend range significantly and offer an enormous benefit for any group or business utilizing them over a large coverage area.  

Weather Interference 

Weather can also affect your radio’s range. Atmospheric conditions, such as rain, fog, snow, and temperature fluctuations all can scatter radio signals and can cause intermittent reception, a reduction on your range, or both. Weather events like thunderstorms can also introduce electromagnetic interference that can cause static or signal degradation. 

Where do two-way radios shine? 

Since two-way radios utilize Frequency Modulation for all their transmissions, their sound quality will not be quite as good as a cellular signal. However, in cases where instant group communication is necessary, especially in circumstances in which there is poor or no cellular coverage, they are the perfect tool.  

What fundamentally sets two-way radios apart is their ability to function even when other infrastructure goes down. Unlike cell phones or internet-based communication systems that rely on networks of cell towers, satellites, and power grids, two-way radios can communicate directly between devices when other communication systems may fail.  

In emergency situations like natural disasters, power outages, or remote locations where traditional communication infrastructure is damaged, inoperable, or nonexistent, these radios become essential tools. When cellular networks go down and internet connections are severed, two-way radios can still enable critical two-way communication—as long as the devices are within range of each other, requiring nothing more than their battery power and a clear line of sight.  

Two-way radios also offer increased durability and better battery life than most cell phones, so they can be used in extremely harsh environments—those in which emergency communications would be particularly critical. Without a reliance on external networks and their simplified push-to-talk function, they are a unique and proven communication alternative for a variety of contexts, both personal and professional.