Radio wave, wavelength, frequency—you’re sure to hear these terms tossed around when discussing two-way radios, but do you know what they mean? The following two-way radio terminology can help you better understand how two-way radios operate. After all, discussing two-way radios can start to feel like a lesson straight out of your college physics book. To simplify things, here’s an introduction to some of the basic terminology behind two-way radio systems.
Radio communication is all about radio waves. Similar to ocean waves, radio waves flow up and down and can alter in how high they peak. But unlike ocean waves they are not visible to the human eye.
Radio waves are measured by the distance between one peak to the next—the space in between is known as the wavelength. A short wavelength relates to closely packed peaks, while long wavelengths are used to describe peak waves that are farther apart.
Radio waves follow a specific pattern known as a ‘cycle.’ The pattern or cycle continues to repeat itself over and over.
The number of cycles that occur every second is defined as the frequency. Radio engineers refer to “cycles per second” in “hertz,” or Hz for short. If someone says the wave frequency is 12 Hertz, that means there are 12 cycles occurring every second. Radio cycles generally repeat thousands of times each second. Engineers use kilohertz (KHz) to represent 1,000 cycles per second, and megahertz (MHz) to represent 1 million cycles per second. Additionally, gigahertz (GHz) translates to 1 billion cycles per second.
The higher the frequency the shorter the wavelength, and visa-versa. Interestingly, the wavelengths between super high frequencies (over 30 GHz) are so small that not even a single drop of water could fit in between the invisible peaks. Better coverage usually relates to lower frequency. VHF low band is credited with the most “effective radiated power” (ERP).
Larger antennas are often required on lower frequency radios to improve communication.
Spectrum is used to define any range of frequencies that could potentially be used for radio communication purposes. Audible frequency range is typically somewhere between 20 and 18,00 cycles per second.
To make frequencies easier to comprehend, radio engineers group them into different categories or ranges, known as bands. Examples of bands include High Frequency (HF), Very High Frequency (VHF), Ultra-High Frequency (UHF), Superhigh Frequency (SF), Extremely High Frequency (EHF), and infrared.
The Federal Communications Commission (FCC) created their own categories to group frequencies, these are known as channels. The FCC is tasked with licensing out channels, and the specific center frequency or carrier frequency of that channel is identified. Radio communication is transmitted over multiple frequencies contained within one channel. The more frequencies contained within one channel, the larger its bandwidth and the more information it can transmit at one time.
The FCC provides an excellent example of this by comparing it to a highway. The wider a highway is, the more vehicles it can transmit at the same time. Think of larger bandwidth like a wider freeway—it can transmit more messages because it has a larger channel to work with. This is slowly changing though as technology advances; the latest microprocessors and software techniques require less bandwidth to transmit the same number of messages compared to 10-years ago. The FCC compares this concept to carpooling.
UHF frequencies that have shorter wavelengths, generally in the 200 to 2,000 MHz range, provide better communication behind closed doors. That’s because they are better at penetrating building openings, like doors or windows, as opposed to VHF frequencies under 200 MHz. Low band VHF offers poor building penetration, while High Band VHF is slightly better.