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Operation
Model 8902A
HP-IB PROGRAM CODES
FREQ ERROR
= S5
MHz =
MZ
MEASUREMENT TECHNIQUE
When the Measuring Receiver is tuned, the IF signal is amplified and limited. If manually tuned, the
RF input frequency is measured and compared to either the keyboard-entered frequency o r to the
frequency measured after the MHz key is pressed. The frequency difference is displayed as frequency
error.
If the Measuring Receiver is automatically tuned, two methods of determining frequency error are
used:
0
When the input signal is greater than 2.5 MHz, the frequency of the actual IF signal is subtracted
from the selected IF frequency
(455
kHz or 1.5 MHz) to determine the frequency error,
0
When the input signal is less than 2.5 MHz, the input signal is passed directly into the IF
without down-conversion. When the signal is first located, the frequency is counted. When the
FREQ ERROR key
is
selected, this first-counted frequency becomes the reference. Subsequent
frequency counts are subtracted from this reference, and the results are displayed as frequency
error.
10 dB
INPUT
IF
IF
ATTENUATOR
RF
AMP
FIf.ER
ATTENUATOR
INPUT
AMP/FILTER
LIMITERS
COUNTER]
VOLTMETER
CONTROLLER
AND DISPLAY
H R t l R t l R R f l t l LW]
RF
Frrqiicwcy Error Mcwsitrc)rnent Ulocl<
Diugrum
COMMENTS
Down-Converted Signals.
The down-converted RF input frequency milst fall within the passband of the IF being used. For
the 1.5 MHz IF, the passband is approximately 3 MHz wide. For the
455
kHz IF, the passband is
approximately 200 kHz wide.
3-148
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