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dB<br />

Linear<br />

scale<br />

6<br />

5<br />

4<br />

3<br />

2<br />

1<br />

log 10 3 = 0.4771 ≅ 48%<br />

lines 2, 3, 5, and 8 will be particularly useful when the various lines<br />

of a log plot are left unnumbered.<br />

Since<br />

log10 1 � 0<br />

log10 10 � 1<br />

log10 100 � 2<br />

log10 1000 � 3<br />

the spacing between 1 and 10, 10 and 100, 100 and 1000, and so on,<br />

will be the same as shown in Figs. 23.1 and 23.2.<br />

•••<br />

LOGARITHMS ⏐⏐⏐ 1019<br />

1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90100<br />

log 10 2 = 0.3010<br />

≅ 30%<br />

% of full width<br />

log 10 4 = 0.6021 ≅ 60%<br />

≅ 70% ≅ 95%<br />

≅ 78% ≅ 90%<br />

≅ 85%<br />

FIG. 23.1<br />

Semilog graph paper.<br />

Log scale<br />

1 2 3 5 8 10 20 30 50 80 100 1 kHz 10 kHz 100 kHz 1 MHz f (log scale)<br />

200<br />

300<br />

500<br />

800<br />

2 kHz<br />

3 kHz<br />

5 kHz<br />

8 kHz<br />

FIG. 23.2<br />

Frequency log scale.<br />

30 kHz<br />

50 kHz<br />

80 kHz<br />

300 kHz<br />

500 kHz<br />

800 kHz

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