MHz stands for megahertz, and it measures frequency: how many times a radio wave oscillates per second. One MHz equals one million cycles per second. When you see a number like 98.7 MHz on your car stereo, it tells you the station’s signal is vibrating 98.7 million times every second.
How Radio Frequency Works
A radio wave is a type of electromagnetic energy that travels through the air in a repeating pattern, similar to ripples on water. Each complete up-and-down cycle counts as one oscillation. The number of oscillations that happen in one second is the wave’s frequency, measured in hertz (Hz). Since radio waves oscillate millions or even billions of times per second, using plain hertz would mean writing out enormous numbers. Megahertz simplifies this: instead of saying a station broadcasts at 101,500,000 Hz, you say 101.5 MHz.
The unit is named after Heinrich Hertz, a German physicist who conducted the first experiments with radio waves in 1887. His work laid the foundation for radio communications and radar. Radio waves were originally called “Hertzian waves,” and the International System of Units later adopted his name for the standard unit of frequency.
What the MHz Number Tells You
Every radio station is assigned a specific frequency so its signal doesn’t overlap with neighboring stations. In the United States, the FM broadcast band runs from 88 MHz to 108 MHz, divided into 100 channels. Each channel is 200 kHz (0.2 MHz) wide, which is why FM stations always end in an odd decimal: 88.1, 88.3, 88.5, and so on. That precise spacing prevents two stations from bleeding into each other.
AM radio operates at much lower frequencies, typically between 540 kHz and 1700 kHz (0.54 to 1.7 MHz). Because AM frequencies are so much lower, they’re usually expressed in kilohertz rather than megahertz.
How Frequency Affects the Signal
Frequency and wavelength have an inverse relationship: the higher the MHz, the shorter the physical length of each wave. FM radio waves in the 88 to 108 MHz range have wavelengths roughly 2.8 to 3.4 meters long. AM radio waves, at their lower frequencies, can stretch hundreds of meters from peak to peak.
This difference has real consequences for how far and how clearly a signal travels. Lower-frequency waves (fewer MHz) tend to bend around obstacles and bounce off the upper atmosphere, which is why AM stations can sometimes be heard hundreds of miles away, especially at night. Higher-frequency waves travel in straighter lines and generally need a clear path between the transmitter and your antenna.
The tradeoff is sound quality. Higher frequencies can carry more data per second, which is why FM radio sounds richer and clearer than AM. AM’s longer wavelengths sacrifice audio fidelity for raw distance.
MHz Beyond Broadcast Radio
The megahertz scale covers far more than your car stereo. Different slices of the radio spectrum are reserved for different purposes, and the MHz number gives you a rough idea of what a signal is designed to do.
- High frequency (HF), 3 to 30 MHz: Used for long-distance shortwave radio, amateur radio, and aviation communication. Wavelengths range from 10 to 100 meters, allowing signals to bounce off the ionosphere and reach across continents.
- Very high frequency (VHF), 30 to 300 MHz: Home to FM radio, television broadcasts, marine radio, and air traffic control. These waves propagate well through the air and pass through many non-metallic materials.
- Ultra high frequency (UHF), 300 to 3,000 MHz: Used for cell phones, Wi-Fi, Bluetooth, walkie-talkies, and GPS. The shorter wavelengths at these frequencies have slightly reduced ability to pass through walls and other obstacles, but they can carry much more information.
Two-way radios like FRS walkie-talkies operate around 462 MHz. Wi-Fi routers commonly use 2,400 MHz (2.4 GHz) and 5,800 MHz (5.8 GHz). Even your microwave oven operates at about 2,450 MHz. In each case, the MHz value defines where on the electromagnetic spectrum that device lives and how its signal behaves in the real world.
Why MHz Matters When Choosing Equipment
If you’re shopping for a scanner, ham radio, or two-way radio, the MHz range determines what you can listen to or transmit on. A VHF radio tuned to 136 to 174 MHz will pick up marine and aviation bands but won’t receive UHF signals used by many businesses and public safety agencies. Dual-band radios solve this by covering both VHF and UHF ranges.
Antenna length also ties directly to frequency. An efficient antenna is typically a fraction of the signal’s wavelength, so higher-MHz radios use shorter antennas. A handheld UHF radio at 460 MHz needs an antenna only about 16 centimeters long, while an HF antenna for 7 MHz might stretch over 20 meters. Matching your antenna to your operating frequency is one of the simplest ways to improve reception and range.