Also known as: VHF, UHF, SHF

Frequency bands are the conventional decade-wide divisions of the radio spectrum: VLF, LF, MF, HF (3–30 MHz), VHF (30–300 MHz), UHF (300 MHz–3 GHz), and SHF (3–30 GHz).¹ Each decade behaves so differently in propagation, antenna size, and available bandwidth that it is treated as a distinct engineering regime.

The radio spectrum divided into bands; VHF and UHF carry most scanner and trunked-radio traffic, while HF relies on ionospheric skip.

How it works

The bands are numbered by order of magnitude, and each decade is centred on a wavelength that governs its behaviour. Because wavelength = c / frequency, HF wavelengths are tens of metres, VHF a few metres, and UHF centimetres to a metre — which directly sets practical antenna size (an efficient antenna is a meaningful fraction of a wavelength).

Propagation is what most distinguishes the bands:

• HF (3–30 MHz) refracts off the ionosphere, giving sky-wave “skip” that can span continents with modest power. Conditions vary with the sun, time of day, and the 11-year solar cycle.
• VHF/UHF (30 MHz–3 GHz) normally punch through the ionosphere and travel in near straight lines, so range is set by the radio horizon and antenna height. This predictability is why land-mobile, aviation, and public-safety systems live here. Occasional tropospheric ducting and sporadic-E can extend VHF far beyond the horizon.
• SHF and above are strongly line-of-sight, offer huge bandwidth for radar, satellite, and 5G, and begin to suffer atmospheric absorption and rain fade.

Higher frequencies also carry more path loss for a given distance and antenna, and penetrate buildings less, trading range for the wide bandwidth that high-rate digital systems need.

In practice

Regulators — coordinated globally by the ITU and administered nationally (the FCC in the US, Ofcom in the UK, and others) — publish band plans that carve each band into slices for broadcast, aviation, marine, amateur, and public-safety use.² For a scanner operator these allocations are the map of where to listen:

• VHF high band (136–174 MHz): marine, aviation voice nearby, older public-safety and business radio.
• UHF (400–520 MHz): business, public-safety, and many trunked systems.
• 700/800 MHz: modern public-safety trunked radio (P25) in North America.

Matching the target allocation to the band determines the whole install: antenna type and size, feedline loss, and whether the SDR’s tuning range even covers it.

Relevance to SDR

Most trunked-radio scanning happens in VHF, UHF, and the 700/800 MHz bands, so those decades drive hardware choices. Matching an SDR’s tuning range and a resonant antenna to the target band is the first hardware decision, ahead of any software configuration. GopherTrunk decodes whatever the front end delivers within its sampled bandwidth; the band determines the antenna, the expected path loss, and which protocols are likely to appear.

Sources

1. Radio spectrum — Wikipedia, the conventional band divisions and their frequency ranges. ↩

2. International Telecommunication Union — Wikipedia, the body that coordinates global spectrum allocation and band plans. ↩

See also

• Electromagnetic spectrum
• Frequency
• Radio propagation
• Ionospheric propagation
• Radio horizon
• Sky-wave propagation
• Path loss

Learn it step by step

• Frequency, bands & the spectrum