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11-12 Broadcast Transmission Systems

UV Band

The UV band is the region of the EM spectrum lying immediately above the visible light band.
The UV band consists of EM radiation with wavelengths extending between the shortest visible
violet (circa 0.4 

µm) and the longest X rays (circa 10 nm), i.e., from 750 THz—approximately 3

ev—up to circa 30 PHz—approximately 100 ev.

2

The UV band is further subdivided into the “near” and the “far” UV segments as follows:

•

Near” UV segment, circa 0.4 

µm down to 100 nm (circa 750 THz up to 3 PHz, approximately

3 ev up to 10 ev)

•

Far UV segment, 100 nm down to circa 10 nm, (3 PHz up to circa 30 PHz, approximately 10
ev up to 100 ev)

The far UV band is also referred to as the vacuum UV band, since air is opaque to all UV radia-
tion in this region.

UV radiation is produced by electron transitions in atoms and molecules, as in a mercury dis-

charge lamp. Radiation in the UV range is easily detected and can cause florescence in some
substances, and can produce photographic and ionizing effects.

In UV astronomy, the emissions of celestial bodies in the wavelength band between 50–320

nm are detected and analyzed to study the heavens. The hottest stars emit most of their radiation
in the UV band.

11.1.2b

DC to Light

Below the IR band are the lower frequency (longer wavelength) regions of the EM spectrum,
subdivided generally into the following spectral bands (by frequency/wavelength):

•

Microwave band, 300 GHz down to 300 MHz (1 mm up to 1 m). Some reference works define
the lower edge of the microwave spectrum at 1 GHz. 

•

Radio frequency (RF) band, 300 MHz down to 10 kHz (1 m up to 30 Km)

•

Power (PF)/telephony band, 10 kHz down to dc (30 Km up to 

∞)

These regions of the EM spectrum are usually described in terms of their frequencies.

Radiations whose wavelengths are of the order of millimeters & centimeters are called micro-

waves, and those still longer are called radio frequency (RF) waves (or Hertzian waves).

Radiation from electronic devices produces EM waves in both the microwave and RF bands.

Power frequency energy is generated by rotating machinery. Direct current (dc) is produced by
batteries or rectified alternating current (ac). 

Microwave Band

The microwave band is the region of wavelengths lying between the far IR/sub-millimeter region
and the conventional RF region. The boundaries of the microwave band have not been definitely
fixed, but it is commonly regarded as the region of the EM spectrum extending from about 1 mm
up to 1 m in wavelengths, i.e. from 300 GHz down to 300 MHz. The microwave band is further
sub-divided into the following segments:

2.  Some references use 4, 5, or 6 nm as the upper edge of the UV band.

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The Electromagnetic Spctrum 11-13

•

Millimeter waves, 300 GHz down to 30 GHz (1 mm up to 1 cm); the EHF band. (Some refer-
ences consider the top edge of the millimeter region to stop at 100 GHz.)

•

Centimeter waves, 30 GHz down to 3 GHz (1 cm up to 10 cm); the SHF band.

The microwave band usually includes the UHF band from 3 GHz down to 300 MHz (from 10 cm
up to 1 m).

Microwaves are used in radar, in communication links spanning moderate distances, as radio

carrier waves in television broadcasting, for mechanical heating, and cooking in microwave
ovens.

Radio Frequency (RF) Band

The RF range of the EM spectrum is the wavelength band suitable for utilization in radio com-
munications extending from 10 kHz up to 300 MHz (from 30 Km down to 1 m). (Some refer-
ences consider the RF band as extending from 10 kHz to 300 GHz, with the microwave band as a
subset of the RF band from 300 MHz to 300 GHz.)

Some of the radio waves in this band serve as the carriers of low-frequency audio signals;

other radio waves are modulated by video and digital information. The amplitude modulated
(AM) broadcasting band uses waves with frequencies between 550–1640 kHz; the frequency
modulated (FM) broadcasting band uses waves with frequencies between 88–108 MHz.

In the U.S., the Federal Communications Commission (FCC) is responsible for assigning a

range of frequencies to specific services. The International Telecommunications Union (ITU)
coordinates frequency band allocation and cooperation on a worldwide basis. 

Radio astronomy uses radio telescopes to receive and study radio waves naturally emitted by

objects in space. Radio waves are emitted from hot gases (thermal radiation), from charged par-
ticles spiraling in magnetic fields (synchrotron radiation), and from excited atoms and molecules
in space (spectral lines), such as the 21 cm line emitted by hydrogen gas. 

Power Frequency (PF)/Telephone Band

The PF range of the EM spectrum is the wavelength band suitable for generating, transmitting,
and consuming low frequency power, extending from 10 kHz down to dc (zero frequency), i.e.,
from 30Km up in wavelength. In the US, most power is generated at 60 Hz (some military and
computer applications use 400 Hz); in other countries, including Europe, power is generated at
50 Hz.

Frequency Band Designations

The combined microwave, RF (Hertzian Waves), and power/telephone spectra are subdivided
into the specific bands given in Table 11.1.1, which lists the international radio frequency band
designations and the numerical designations. Note that the band designated (12) has no com-
monly used name or abbreviation.

The radar band often is considered to extend from the middle of the HF (7) band to the end of

the EHF (11) band. The current US Tri-Service radar band designations are listed in Table
11.1.2.

An alternate and more detailed sub-division of the UHF (9), SHF (10), and EHF (11) bands is

given in Table 11.1.3.

Several other frequency bands of interest (not exclusive) are listed in Tables 11.1.4–11.1.6.

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11-14 Broadcast Transmission Systems

Table 11.1.1 Frequency Band Designations

Description

Band Designation

Frequency

Wavelength

Extremely Low Frequency

ELF (1) Band

3 Hz up to 30 Hz

100 Mm down to 10 Mm

Super Low Frequency

SLF (2) Band

30 Hz up to 300 Hz

10 Mm down to 1 Mm

Ultra Low Frequency

ULF (3) Band

300 Hz up to 3 kHz

1 Mm down to 100 Km

Very Low Frequency

VLF (4) Band

3 kHz up to 30 kHz

100 Km down to 10 Km

Low Frequency

LF (5) Band

30 kHz up to 300 kHz

10 Km down to 1 Km

Medium Frequency

MF (6) Band

300 kHz up to 3 MHz

1 Km down to 100 m

High Frequency

HF (7) Band

3 MHz up to 30 MHz

100 m down to 10 m

Very High Frequency

VHF (8) Band

30 MHz up to 300 MHz

10 m down to 1 m

Ultra High Frequency

UHF (9) Band

300 MHz up to 3 GHz

1 m down to 10 cm

Super High Frequency

SHF (10) Band

3 GHz up to 30 GHz

10 cm down to 1 cm

Extremely High Frequency

EHF (11) Band

30 GHz up to 300 GHz

1 cm down to 1 mm 

—

(12) Band

300 GHz up to 3 THz

1 mm down to 100 

µ

Table 11.1.2 Radar Band Designations

Band

Frequency

Wavelength

A Band

0 Hz up to 250 MHz

∞

 down to 1.2 m

B Band 

250 MHz up to 500 MHz

1.2 m down to 60 cm

C Band

500 MHz up to 1 GHz

60 cm down to 30 cm

D Band

1 GHz up to 2 GHz

30 cm down to 15 cm

E Band

2 GHz up to 3 GHz

15 cm down to 10 cm

F Band

3 GHz up to 4 GHz

10 cm down to 7.5 cm

G Band

4 GHz up to 6 GHz

7.5 cm down to 5 cm

H Band

6 GHz up to 8 GHz

5 cm down to 3.75 cm

I Band 

8 GHz up to 10 GHz

3.75 cm down to 3 cm

J Band

10 GHz up to 20 GHz

3 cm down to 1.5 cm

K Band

20 GHz up to 40 GHz

1.5 cm down to 7.5 mm

L Band

40 GHz up to 60 GHz

7.5 mm down to 5 mm)

M Band

60 GHz up to 100 GHz

5 mm down to 3 mm

N Band

100 GHz up to 200 GHz

3 mm down to 1.5 mm

O Band

200 GHz up to 300 GHz

1.5 mm down to 1 mm

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The Electromagnetic Spctrum 11-15

Table 11.1.3 Detail of UHF, SHF, and EHF Band Designations 

Band

Frequency

Wavelength

L Band

1.12 GHz up to 1.7 GHz

26.8 cm down to 17.6 cm

LS Band

1.7 GHz up to 2.6 GHz

17.6 cm down to 11.5 cm

S Band

2.6 GHz up to 3.95 GHz 

11.5 cm down to 7.59 cm

C(G) Band

3.95 GHz up to 5.85 GHz

7.59 cm down to 5.13 cm

XN(J, XC) Band

5.85 GHz up to 8.2 GHz

5.13 cm down to 3.66 cm

XB(H, BL) Band

7.05 GHz up to 10 GHz

4.26 cm down to 3 cm

X Band

8.2 GHz up to 12.4 GHz

3.66 cm down to 2.42 cm

Ku(P) Band

12.4 GHz up to 18 GHz

2.42 cm down to 1.67 cm

K Band

18 GHz up to 26.5 GHz

1.67 cm down to 1.13 cm

V(R, Ka) Band

26.5 GHz up to 40 GHz

1.13 cm down to 7.5 mm

Q(V) Band

33 GHz up to 50 GHz

9.09 mm down to 6 mm

M(W) Band

50 GHz up to 75 GHz

6 mm down to 4 mm

E(Y) Band

60 GHz up to 90 GHz 

5 mm down to 3.33 mm

F(N) Band

90 GHz up to 140 GHz

3.33 mm down to 2.14 mm

G(A)

140 GHz p to 220 GHz

2.14 mm down to 1.36 mm

R Band

220 GHz up to 325 GHz

1.36 mm down to 0.923 mm

Table 11.1.4 Low Frequency Bands of Interest 

Band

Frequency

Sub-sonic band

0 Hz–10 Hz

Audio band

10 Hz–10 kHz

Ultra-sonic band

10 kHz and up

Table 11.1.5 Applications of Interest in the RF Band

Band

Frequency

Longwave broadcasting band

150–290 kHz

AM broadcasting band

550–1640 kHz (1.640 MHz), 107 channels, 10 kHz separation 

International broadcasting band

3–30 MHz

Shortwave broadcasting band

5.95–26.1 MHz (8 bands)

VHF TV (Channels 2 - 4)

54–72 MHz

VHF TV (Channels 5 - 6)

76–88 MHz

FM broadcasting band

88–108 MHz

VHF TV (Channels 7 - 13)

174–216 MHz

UHF TV (Channels 14 - 69)

512–806 MHz

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The Electromagnetic Spectrum

11-16 Broadcast Transmission Systems

11.1.2c

Light to Gamma Rays

Above the UV spectrum are the higher frequency (shorter wavelength) regions of the EM spec-
trum, subdivided generally into the following spectral bands (by frequency/wavelength):

•

X ray band, approximately 10 ev up to 1 Mev (circa 10 nm down to circa 1 pm), circa 3 PHz
up to circa 300 EHz

•

Gamma ray band, approximately 1 Kev up to 

∞ (circa 300 pm down to 0 m), circa 1 EHz up to

∞

These regions of the EM spectrum are usually described in terms of their photon energies in
electron volts. Note that the bottom of the gamma ray band overlaps the top of the X ray band.

It should be pointed out that cosmic “rays” (from astronomical sources) are not EM waves

(rays) and, therefore, are not part of the EM spectrum. Cosmic “rays” are high energy charged
particles (electrons, protons, and ions) of extraterrestrial origin moving through space, which
may have energies as high as 10

20

 ev. Cosmic “rays” have been traced to cataclysmic astrophysi-

cal/cosmological events, such as exploding stars and black holes. Cosmic “rays” are emitted by
supernova remnants, pulsars, quasars, and radio galaxies. Comic “rays” that collide with mole-
cules in the Earth’s upper atmosphere produce secondary cosmic “rays” and gamma rays of high
energy that also contribute to natural background radiation. These gamma rays are sometimes
called “cosmic” or secondary gamma rays. Cosmic rays are a useful source of high-energy parti-
cles for certain scientific experiments.

Radiation from atomic inner shell excitations produces EM waves in the X ray band. Radia-

tion from naturally radioactive nuclei produces EM waves in the gamma ray band.

X Ray Band

The X ray band is further sub-divided into the following segments:

•

Soft X rays, approximately 10 ev up to 10 Kev (circa 10 nm down to 100 pm), circa 3 PHz up
to 3 EHz

•

Hard X rays, approximately 10 Kev up to 1Mev (100 pm down to circa 1 pm), 3 EHz up to
circa 300 EHz

Because the physical nature of these rays was first unknown, this radiation was called X rays.

The more powerful X rays are called hard X rays and are of high frequencies and, therefore, are
more energetic; less powerful X rays are called soft X rays and have lower energies.

X rays are produced by transitions of electrons in the inner levels of excited atoms or by rapid

deceleration of charged particles (Brehmsstrahlung or breaking radiation). An important source
of X rays is synchrotron radiation. X rays can also be produced when high energy electrons from
a heated filament cathode strike the surface of a target anode (usually tungsten) between which a
high alternating voltage (approximately 100 kV) is applied.

X rays are a highly penetrating form of EM radiation and applications of X rays are based on

their short wavelengths and their ability to easily pass through matter. X rays are very useful in
crystallography for determining crystalline structure and in medicine for photographing the
body. Because different parts of the body absorb X rays to a different extent, X rays passing
through the body provide a visual image of its interior structure when striking a photographic
plate. X rays are dangerous and can destroy living tissue. They can also cause severe skin burns.
X rays are useful in the diagnosis and non-destructive testing of products for defects.

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The Electromagnetic Spectrum