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Appendix 3:
Electromagnetic frequency bands
For convenience, the EM frequency spectrum has been
divided up into arbitrary ‘bands’, each of which has been
alotted an identifying number (radio) or letter (radar):
Radio
The following terminology is that agreed by the CCIR:
Band 4, v.l.f. (very low frequency), 3–30 kHz; Band 5, l.f.,
30–300 kHz; Band 6, m.f. (medium), 300–3,000 kHz
(3 MHz); Band 7, h.f. (high), 3–30 MHz; Band 8, v.h.f.
(very high), 30–300 MHz; Band 9, u.h.f. (ultra-high),
300–3,000 MHz (3 GHz); Band 10, s.h.f. (super-high),
3–30 GHz; Band 11, e.h.f. (extremely high), 30–300 GHz;
Band 12 (awaiting a name), 300–3,000 GHz (3 THz).
Radar
During World War 2, to assist security, radar wavebands
were given arbitrary letters: P-band, 0.225–0.39 GHz; L,
0.39–1.55; S, 1.55–5.2; X, 5.2–10.9; K, 10.9–36; Q, 36–46;
V, 46–56.
From 1946 several schemes proliferated. For radar, one
authority divided the spectrum into convenient wavelengths,
resulting in (figures rounded off): L, 1–2 GHz; S,
2–4; C, 4–8; X, 8–13 [in US sometmes 12.5]; Q (changed
to Ku), 13–20; K, 20–30; Ka, 30–40.
European usage centred on: P, 80–390 MHz; L, 390–2,500
MHz (2.5 GHz); S, 2.5–4.1 GHz; C, 4.1–7.0 GHz; X,
7.0–11.5 GHz; J, 11.5–18.0 GHz; K, 18–33 GHz; O,
33–40 GHz; Q, 40–60 GHz; V, 60–90 GHz.
The ITU refined this to the following, now [from 1984]
actually nominated for worldwide use: v.h.f., 138–144 and
216–225 MHz; u.h.f., 420–450 and 890–942 MHz; L,
1.215–1.4 GHz; S, 2.3–2.5 GHz; C, 5.25–5.925 GHz; X,
8.5–10.68 GHz; Ku, 13.4–14.0 and 15.7–17.7 GHz; K,
24.05–24.25 GHz; Ka, 33.4–36.0 GHz; V, 59–64 GHz; W,
76–81 GHz, 92–100 GHz; mm, 126–142, 144–149,
231–235 and 238–248 GHz.
A different rationalized version has been adopted for
space communications (not with GPS):
L, 0.39–1.55 GHz; S, 1.55–5.2 GHz; C [overlapping S and
X], 3.7–6.2 GHz; X, 5.2–10.9 GHz; Ku, 15.35–17.25 GHz;
K, 10.9–36.0 GHz; Ka, 33–36 GHz.
In 1977 the US introduced a supposed definitive system
covering an expanded range. This was adopted for electronic
countermeasures, but the ‘old’ systems are still
commonly used for military radar:
h.f., 10–30 MHz; v.h.f., 30–100 MHz; A, 100–300 MHz;
B, 300–500 MHz (0.5 GHz); C, 0.5–1 GHz; D, 1–2 GHz;
E, 2–3 GHz; F, 3–4 GHz; G, 4–6 GHz; H, 6–8 GHz; I,
8-10 GHz; J, 10–20 GHz; K, 20–40 GHz; L, 40–60 GHz;
M, 60–100 GHz.
This system was adopted by NATO, but with the longer
wavelengths changed to: A, 0–250 MHz; B, 250–500
MHz.
Light
For completeness, at frequencies higher than those listed
above, the microwaves of radar give way to IR (infra-red).
From this point it is more common to cite wavelength, the
reciprocal of frequency. IR covers a range of wavelengths
roughly extending from 100 μ (10 –4 m) down to 0.75 μ. As
wavelength is reduced further, the light becomes visible to
the human eye, disappearing again into the UV (ultraviolet)
at about 0.75 μ.
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