The bands at a glance
LF and MF (30 kHz to 3 MHz): long and medium waves, ground wave, AM broadcast, amateur 2200 m, 630 m and 160 m. HF (3 to 30 MHz): shortwave, ionospheric propagation, worldwide communication, amateur bands from 80 m to 10 m, CB around 27 MHz. VHF (30 to 300 MHz): line of sight, 6 m, 2 m, FM broadcast, airband, marine radio. UHF (300 MHz to 3 GHz): 70 cm, PMR446, TV, mobile phones, LoRa and ISM at 868 and 915 MHz, GPS, 23 cm, Wi-Fi at 2.4 GHz.
What changes with frequency
Wavelength shrinks (300 m at 1 MHz, 2 m at 145 MHz, 12 cm at 2.4 GHz) and so does antenna size. Free-space path loss rises by 6 dB every time the frequency doubles for the same distance and gains. Diffraction around hills gets worse, building penetration changes and the noise from the environment falls: man-made and galactic noise dominate on HF while the receiver itself is the limit on UHF.
Choosing a band for a link
For a few kilometres in a city, UHF handhelds work well; for rural coverage over a valley a VHF antenna on a hill may do better; for continental or world coverage only HF can do it without infrastructure. Enter your frequency in the coverage map and the engine switches model automatically.
