Radio Band C Frequency

C-band: 4–8 GHz radio frequencies

IEEE 521 puts the C-band between 4 GHz and 8 GHz. That works out to wavelengths from 3.75 cm up to 7.5 cm, since frequency and wavelength are tied together by f = c / λ with c ≈ 3 × 10⁸ m/s. On the satellite side, the traditional split has been 3.7–4.2 GHz for downlink and 5.925–6.425 GHz for uplink. Wi-Fi 5 (802.11ac/ax) lives in the nearby 5.0–5.8 GHz unlicensed range.

What makes C-band valuable is how little rain bothers it. Attenuation here runs well below what you see in Ku or Ka, so it stays the band of choice for satellite work in tropical and equatorial areas that get hit with heavy rainfall. You pay for that with antenna size: reception usually needs dishes in the 1.8–3 m range, considerably bigger than a Ku-band setup.

Applications

You will find it behind geostationary fixed-satellite services such as TV distribution and VSAT, NOAA weather radars (the ones around 5.6 GHz, for instance), Wi-Fi networks on 5 GHz, and terrestrial microwave links. The lower end of the band has since been carved up for 5G NR FR1, the 3.5 GHz mid-band, which means the new networks have to coexist with satellite operators who were there first.

FAQ

Why is C-band used for tropical satellite TV? Rain barely touches the signal at 4–6 GHz compared with Ku or Ka, so the link holds up through the kind of downpours you get in equatorial climates.

Was C-band reallocated to 5G in Brazil? It was. ANATEL’s 2021 5G auction (Edital) handed the 3.5 GHz range (3.3–3.7 GHz) to 5G NR FR1, which meant coordinating with legacy satellite downlinks through filters and a cleanup of the band.

What is the difference between C-band and Ku-band? It comes down to a trade. C-band (4–8 GHz) shrugs off rain but wants bigger dishes. Ku-band (12–18 GHz) lets you use smaller antennas, at the cost of taking a harder hit in heavy rain (“rain fade”).