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Short note: Radio frequency spectrum

Short answer

The radio spectrum 3 kHz–300 GHz is divided by ITU into VLf to EHF bands. Each band has characteristic propagation: VLF/LF ground wave, MF ground/sky wave, HF sky wave, VHF/UHF space wave. Higher frequencies allow smaller antennas and wider bandwidth but suffer greater atmospheric absorption.

Write a short note on radio frequency spectrum.

The radio frequency (RF) spectrum is the part of the electromagnetic spectrum used for radio communication, roughly 3 kHz to 300 GHz. ITU divides it into bands, each a decade in frequency, and each band has its own propagation mode and uses.

BandFrequencyWavelengthMain propagationTypical use
VLF3–30 kHz100–10 kmGround wave, earth–ionosphere waveguideSubmarine, navigation
LF30–300 kHz10–1 kmGround waveLW broadcast, beacons
MF0.3–3 MHz1000–100 mGround wave (day), sky wave (night)AM broadcast
HF3–30 MHz100–10 mSky wave (ionosphere)SW broadcast, long-distance links
VHF30–300 MHz10–1 mSpace wave (LOS)FM, TV, aircraft radio
UHF0.3–3 GHz1 m–10 cmSpace wave, troposcatterTV, mobile, GPS, Wi-Fi
SHF3–30 GHz10–1 cmLOS, satelliteMicrowave links, radar, satellite
EHF30–300 GHz10–1 mmLOS (rain/gas absorption)Radar, 5G mmWave, radio astronomy

Key trends: as frequency increases, ground-wave range falls, the ionosphere stops returning the wave (above ≈ 30 MHz), antennas become smaller and more directive, available bandwidth increases, and absorption by rain and gases rises. The spectrum is a limited natural resource, so its use is regulated by the ITU internationally and by the Nepal Telecommunications Authority (NTA) in Nepal.

✓ Answer checked by Claude Opus 5.5 (high effort)

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