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Operation
Model 8902A
mode when modulation rates exceed 1 kHz. Also, Track Mode tuning is not recommended where
optimum noise performance is required.
Manual Tuning-Low-Noise LO.
The instrument tunes to the frequency keyed into it, via the keyboard, regardless of whether a signal
is present, Once tuned, the LO is locked to an internal voltage-controlled, crystal oscillator for high
stability and low noise. Once locked, tuning does not change unless a new frequency is entered,
Track Mode is selected, the tuning is stepped
u p
or down using the kHz
fi
or kHz
4
keys, Automatic
Operation or Instrument Preset is selected. The manual tune mode is entered immediately when
either MHt, kHz
9,
or kHz
is selected: or if Range Hold is selected. (Note that this tune mode can
be used for tuned R F level measurements when used in conjunction with Special Function 32.9.l
Refer to Tiincd R F LcwI comment, "32.9 SPCL: Tuned RF Level Measurements Using Track-Mode
Tuning" on page 3-105.)
Manual Tuning-Track Mode.
The Measuring Receiver tunes to the keyed-in frequency in the same way as described in the previous
paragraph. However, the LO is not locked to an internal oscillator; instead the LO is locked t o the
input signal itself and tracks it as it drifts. This fiinction is useful for measuring second or third
harmonic signals and for tracking spurious signals.
PROCEDURE
Select FREQ.
Tune Mode Selection:
TRACK
MODE).
numeric entry), o r with RANGE HOLD.
by selecting TRACK MODE again.)
0
Select automatic tuning with AUTOMATIC OPERATION or AUTO TUNING (Blue Key,
0
Select manual tuning with either MHz or one of the kHz keys (with or without a preceding
0
Select track mode with TRACK MODE. (Return from the track mode to the low-noise mode,
Manual Tuning by Keyboard Entry:
To
manually tune to a specific signal frequency, enter the frequency in MHz via the numeric
keyboard, then press the MHz key.
The MHz key can also be used alone to aid in tuning: if the Measuring Receiver is tuned close but
not exactly to the input signal, select MHz to center the signal in the IF passband. If in automatic
tuning mode, and no signal is present, select MHz alone to tune the Measuring Receiver to the last
frequency at which a signal was successfiilly tuned. (If no previous successfir1 tuning has been made,
the Measuring Receiver tunes to 100 MHz.)
RF Frequency Stepping:
To step the tuning of the Measuring Receiver, enter the desired frequency step size in kHz via the
numeric keyboard, then press either kHz
. h
or kHz
4.
Once the step size has been set, either kHz key
will change
%e
tuning by that step size each time the key is pressed. (At power-up, the step size is
set to
0
kHz.)
This spccial function is not availablc with Grmwarc datc codcs 234.1985 and bclow. (To display thc Grmwarc datc codc. sclcct
42.0 SPCL.) To order a ROM set that contains this special function. contact the nearest HP sales oflice.
3-142
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