HP 8901B Operation And Calibration Manual page 319

Operation Model 8901B
HP-IB PROGRAM CODES
The HP-IB codes for selecting various combinations of RF and IF filters are provided in "PROCE-
DURE".
BLOCK DIAGRAM
455 kHz
VOLTMETER
AN0 DISPLAY
LOCAL
OSCILLATOR
Block Diagram
of
RF and IF Filters
COMMENTS
Default Condition
When the instrument is first powered up or when Automatic Operation or Instrument Preset is selected,
RF and IF Filters are placed in the automatic selection mode.
Automatic Retuning
When a new IF is selected, the instrument immediately retunes.
Increased Sensitivity and Selectivity
Many measurements can typically be made on very low-level signals. Using the narrow bandwidth of
the
455
kHz IF for signal frequencies less than
2.5
MHz (but in the manual down-convert mode) or
greater than 10 MHz increases the sensitivity and selectivity of the Modulation Analyzer. (There are,
however, restrictions on modulation, and measurement accuracy may decrease.) Manual deletion of RF
input attenuation also increases sensitivity. (Refer to RF Input Attenuation on page
3-231.)
3-230
Filters, RF and
IF