Radio Frequency (RF) Explained

Radio frequency (abbreviated RF, rf, or r.f.) is a term that refers to alternating current (AC) having characteristics such that, if the current is input to an antenna

What is Radio Frequency?

Radio frequency (RF) refers to alternating current with characteristics such that, when fed to an antenna, it generates an electromagnetic field suitable for wireless broadcasting or communication. Every two-way radio, GPS tracker, and satellite communicator MSL supplies relies on this same underlying physics, just tuned to different parts of the spectrum for different jobs.

These frequencies span a huge portion of the electromagnetic spectrum, from 9 kHz (the lowest allocated wireless communications frequency) up to thousands of gigahertz. When an RF current is supplied to an antenna, the resulting electromagnetic field propagates through space, commonly called a radio wave. Any RF field has a wavelength inversely proportional to its frequency: if f is the frequency in megahertz and the wavelength is measured in metres, wavelength ≈ 300 / f.

At 9 kHz, the free-space wavelength is roughly 33 kilometres. At the highest radio frequencies, wavelengths shrink to around one millimetre. Push the frequency higher still and you move out of the RF spectrum entirely, into infrared, visible light, ultraviolet, X-rays, and gamma rays.

Two-way radios, GPS systems, satellite communications, cordless devices, and broadcast services all operate somewhere in the RF spectrum. A few devices, like TV remotes, operate at infrared or visible-light frequencies instead, with shorter wavelengths than RF.

The RF Spectrum Bands

The RF spectrum is divided into bands, each generally representing a tenfold increase in frequency over the last. The two highest bands, SHF and EHF, are often referred to as the microwave spectrum.

Designation	Abbreviation	Frequencies	Free-space Wavelengths
Very Low Frequency	VLF	9 kHz - 30 kHz	33 km - 10 km
Low Frequency	LF	30 kHz - 300 kHz	10 km - 1 km
Medium Frequency	MF	300 kHz - 3 MHz	1 km - 100 m
High Frequency	HF	3 MHz - 30 MHz	100 m - 10 m
Very High Frequency	VHF	30 MHz - 300 MHz	10 m - 1 m
Ultra High Frequency	UHF	300 MHz - 3 GHz	1 m - 100 mm
Super High Frequency	SHF	3 GHz - 30 GHz	100 mm - 10 mm
Extremely High Frequency	EHF	30 GHz - 300 GHz	10 mm - 1 mm

Why This Matters for Choosing Equipment

For most MSL customers, the practical takeaway sits in the VHF and UHF bands. VHF (30-300 MHz) travels further over open ground and water, which is why it's the standard for marine radio and rural or farm use. UHF (300 MHz-3 GHz) has shorter wavelengths that handle buildings, vehicles, and dense terrain better, which is why it's the standard for construction sites, forestry, and urban operations.

Understanding where your application sits on this spectrum helps explain why a marine VHF radio and a construction UHF radio aren't interchangeable, and why the right choice depends on your environment, not just the price tag.

Not sure whether VHF or UHF suits your operation? The team at Mobile Systems Limited can talk you through the right frequency band and equipment for your specific environment. Get in touch with our team.