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double 2 pole Butterworth band pass filter. The two parts of the filter are
separated by an amplifier section. The 1000Hz and 316Hz analysis band-
widths are selected in this section. The sensitivity of the filter may be
adjusted by potentiometers (FILTER SENSITIVITY ADJUSTMENTS)
situated on the rear panel, see Preliminary Adjustments and Calibration,
section 3. 1.4.
3rd Mixer
The output from the second mixer is fed into another band pass filter,
centre frequency 30 kHz, which further suppresses the image frequency of
31.5 kHz. From the filter the output signal is fed into a balanced modulator
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1
2
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5
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7
Bandwidths from centre frequency
171104
Fig.5.8. Typical filter characteristics
•
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