Radio Band L Frequency

L-band radio frequencies (1–2 GHz)

Under the IEEE radar scheme, the L band runs from 1–2 GHz. That maps to wavelengths of roughly 15–30 cm, since frequency times wavelength equals the speed of light. Run the numbers through f (MHz) = 300 / λ (m) and a 21 cm wavelength lands at 1420 MHz, well inside the L band. That one is the famous hydrogen line radioastronomers watch.

What makes the L band so popular is the balance it strikes: it punches through light obstacles like foliage and drizzle, yet the antennas stay a manageable size. Atmospheric loss is small. The catch these days is interference, since so many services crowd into the same GHz.

Applications

The list is long. GPS L1 (1575.42 MHz), L2 (1227.60 MHz) and L5 (1176.45 MHz) live here, and Galileo, GLONASS and BeiDou GNSS sit in neighbouring bands. Add mobile telephony LTE bands 1, 3 and others, Iridium and Inmarsat satphones, and a stack of aeronautical gear: DME, ADS-B (1090 MHz), TCAS and SSR transponders. The amateur radio 23 cm band (1240–1300 MHz, licenced by Anatel in Brazil) shares the space, as does radio astronomy with the HI line at 1420 MHz. The ITU and the national regulator (Anatel in Brazil, FCC in the US) keep these assignments coordinated so nobody jams anybody.

FAQ

Why is GPS in the L band? It splits the difference between three problems: ionospheric delay gets worse lower down, atmospheric absorption gets worse higher up, and you still want a small antenna. A quarter-wave patch at 1.5 GHz comes out around 5 cm wide.

Can I receive ADS-B at home? Easily. A $25 RTL-SDR USB stick and a 1090 MHz quarter-wave antenna will pull in airliners 200 km away once you run software like dump1090 or Virtual Radar Server.

Does 5 G use the L band? It does. Several 5 G NR FR1 bands (n1, n3, n66) fall in the 1.4–2.2 GHz range, reusing spectrum that LTE held before.