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~
3.16 Hz
10Hz
31.6 Hz
100Hz
x0.1
10
-
-
-
x1
10
100
100
-
x10
10
100
1000
1000
Table 5.5. Pull-in range of the A. F. C. Figures are given in Hz (Limit 0.5 dB
error in level)
~
3.16 Hz
10Hz
31.6 Hz
100Hz
x0.1
1
-
-
-
x1
1
20
20
-
x10
1
20
200
400
Table 5.6.
Pull-in speed of A.F.C. Figures are given in Hz/sec. (Limit
0.
5 dB error in level)
front panel. The A.F.C. only operates in the four lower bandwidths
(3.16 Hz to 100Hz). The A.F.C. consists of a phase detector which com-
pares the phase between a point in the third mixer and the output from the
mixer, and produces a D.C. voltage depending on the phase difference. At a
resonance point, where the phase difference is 90°, no DC voltage is pro-
duced. At a point away from the resonance, the DC voltage produced is fed
into the V.C.O. until the resonance frequency is again reached.
The pull-in capability of the A.F.C. circuit depends on the scale range
and the chosen bandwidth. The pull-in ranges are shown in Table 5.5. The
pull-in or tracking speed of the A.F.C. circuit also depends on the scale
range and bandwidth. The pull-in speeds are shown in Table 5.6.
58
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