Radio Frequency by Steve Winder and Joe Carr - HTML preview

1.2 The radio frequency spectrum

The electromagnetic wave spectrum is shown in Figure 1.2: the part usable for radio communication ranges from below 10 kHz to over 100 GHz.

1

 

Visible spectrum

Infra-red Untra
rays or violet
radiant heat

Radio frequencies Gamma rays VLF LF MF HF VHF UHF SHF EHF
Audio frequencies_X-rays Cosmic rays
Hz kHz MHz MHz
10 100 1 10 100 1 10 10² 10³10⁴ 10⁵ 10⁶ 10⁷ 10⁸ 10⁹10¹⁰10¹¹10¹²10¹³10¹⁴10¹⁵10¹⁶ Frequency
10⁷ 10⁶ 10⁵ 10⁴1000100 10 1 10 1 10¹ 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷ 10⁸ 10⁹10¹⁰10¹¹10¹² Wavelength mm cm
Figure 1.2 The electromagnetic wave spectrum

The radio spectrum is divided into bands and the designation of the bands, their principal use and method of propagation is shown in Table 1.1. Waves of different frequencies behave differently and this, along with the amount of spectrum available in terms of radio communication channels in each band, governs their use.

Table 1.1 Use of radio frequencies Frequency band Designation, use and propagation
3–30 kHz
30–300 kHz
300–3000 kHz
3–30 MHz
30–300 MHz
300–3000 MHz
3–30 GHz Above 30 GHz

Very low frequency (VLF). Worldwide and long distance communications. Navigation. Submarine communications. Surface wave.

Low frequency (LF). Long distance communications, time and frequency standard stations, long-wave broadcasting. Ground wave.

Medium frequency (MF) or medium wave (MW). Medium-wave local and regional broadcasting. Marine communications. Ground wave.

High frequency (HF). ‘Short-wave’ bands. Long distance communications and short-wave broadcasting. Ionospheric sky wave.

Very high frequency (VHF). Short range and mobile
communications, television and FM broadcasting. Sound broadcasting. Space wave.

Ultra high frequency (UHF). Short range and mobile
communications. Television broadcasting. Point-to-point links. Space wave. Note: The usual practice in the USA is to designate 300–1000 MHz as ‘UHF’ and above 1000 MHz as ‘microwaves’.

Microwave or super high frequency (SHF). Point-to-point links, radar, satellite communications. Space wave.
Extra high frequency (EHF). Inter-satellite and micro-cellular radio-telephone. Space wave.