Hz, MHz, GHz — the frequency ladder from AM radio to WiFi
Every wireless technology sits somewhere on a single continuous scale from 3 kHz to 300 GHz. Once you memorise the ladder, every spec sheet becomes readable.
The ITU divides the radio spectrum into eight decade-wide bands and assigns each a name. Consumer wireless spans four of them, and the boundaries between them explain why WiFi cannot penetrate walls as well as FM radio, and why 5G mmWave needs a base station on every block.
The bands
VLF (very low freq): 3–30 kHz — submarine communications > LF: 30–300 kHz — longwave radio, time signals (WWVB 60 kHz) > MF: 300 kHz – 3 MHz — AM broadcast (530–1710 kHz) > HF: 3–30 MHz — shortwave, amateur radio > VHF: 30–300 MHz — FM broadcast (88–108 MHz), TV low, aviation > UHF: 300 MHz – 3 GHz — TV, mobile phones, WiFi 2.4 GHz > SHF: 3–30 GHz — satellite, WiFi 5 GHz, 5G sub-6, radar > EHF: 30–300 GHz — 5G mmWave (24–39 GHz), automotive radar
Wavelength vs frequency
λ = c/f. At 100 MHz FM: 3 m wavelength. At 2.4 GHz WiFi: 12.5 cm. At 28 GHz 5G mmWave: 1.07 cm. Antenna size scales with wavelength — an efficient dipole is λ/2. This is why AM towers are hundreds of metres tall, FM antennas are 1.5 m, and 5G mmWave antennas are the size of a postage stamp (but grouped in arrays of 64+).
Why higher frequency needs more base stations
Free-space path loss increases with f². Rain, foliage and building materials attenuate more at higher f. At 700 MHz (a mobile band), a cell covers many kilometres. At 28 GHz mmWave, coverage drops to 200 m and any wall becomes opaque. Deploying 5G mmWave requires roughly 20× the site density of a 700 MHz network.
Worked example — a WiFi speed vs range trade-off
WiFi 6 in the 2.4 GHz band offers wider coverage (30 m indoors) but limited throughput (~600 Mbps). The same standard at 5 GHz halves the range to 15 m but doubles peak throughput. At 6 GHz (WiFi 6E) throughput doubles again but walls attenuate more sharply. Same protocol, three physical trade-offs governed entirely by frequency.
The five-second recap
kHz = AM. MHz = FM and TV. Low GHz = WiFi and mobile. Tens of GHz = 5G mmWave and radar. Wavelength × frequency = speed of light.
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FAQ
Why is FM 88–108 MHz?+
Historical spectrum allocation from the 1940s. The band width (20 MHz) allows about 100 channels at 200 kHz spacing.
Is 5G faster than WiFi?+
Peak speeds are similar at similar frequencies. Real-world speed depends on cell load and distance more than the standard itself.
What's above 300 GHz?+
Terahertz radiation (0.3–3 THz), then infrared. THz communications is an active research area for 6G.
This article was written by The Turbo Unit Converter engineering desk (RF & telecommunications) and last reviewed on 2026-06-28 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.