HP 8901B Operation And Calibration Manual page 92

Extending Operation
2-5
Extending
Operation
If
You
Need to Know: Refer to:
Frequency
How
to tune to the input signal
when other RF signals or harmonics
are present..
.........................
0
How
to retune to a new input
frequency
............................
How
to tune to a noisy input signal.
How
to track a drifty input signal
.
.
How
to measure the frequency of
input signals above 1300 MHz
......
How
to measure the frequency of
input signals below 150
kHz
......
Amplitude
How
to tune to an input signal whose
amplitude is very unstable..
........
Increasing Selectivity (2-5)
Changing Frequency
(2-6)
Noisy Signal (2-6)
Driffy Signal
(2-7)
Frequency Overrange
(2-7)
Frequency Underrange
(2-7)
Unstable Signal
(2-7)
Increasing Selectivity
The HP 8901Bs Auto Tuning mode is able to automatically find and tune to
the fundamental in a harmonically-rich spectrum as long as the fundamental
is at least 10 dB above the level of the second and third harmonics. The
HP 8901B will also auto tune to the input signal
if
it is at least 30 dB above
all non-harmonically-related
RF
signals. If, however, your input signal does
not meet these criteria, the HP 8901B may have
difi5culty
auto tuning to the
desired input signal. If the instrument does not display the frequency of the
desired input signal, manually tune the HP 8901B to the input frequency by
keying in the frequency of the input signal and then pressing the MHz key.
To minimize the possibility of unwanted low-frequency, harmonic,
or spurious signals entering the IF passband, a high-pass RF filter and
bandpass IF filters can be selected. Table
2-2
shows the possible filter
combination selections.