Fig. 2-15. Adjusting
FINE
RF
CENTER
FREQ
control
for
phase
lock
operation.
When searching a frequency band, set the MIXER PEAK-
divisions of signal. Tune the spectrum null point away from the
ING control to SEARCH position and tune slowly through
sweep starting point, with the RF CENTER FREQUENCY control.
the band with the RF CENTER FREQUENCY control. This
ensures that signals of sufficient power within a tunable range
the FINE RF or IF CENTER FREQ control to move the sweep
will be observed. See Mixer Peaking. After the signal has
start off a spectrum null point. See Fig. 2-14.
been located adjust the MIXER PEAKING to optimize signal
amplitude.
When the SOURCE switch is in the LINE position, the dis-
play is triggered from a sample of the power input line
NOTE
frequency. This feature provides a stable display when the
signal is time-related to the line frequency.
MIXER PEAKING control must not be in the SEARCH
position when making relative amplitude measure-
External triggering requires a signal equal to or greater
ments and should be adjusted for maximum signal
then 0,2 V, within the frequency range of 20 Hz to 100 kHz,
amplitude.
to trigger the sweep. The signal is applied to the TRIG IN
connector on the rear panel. External triggering will pro-
vide a stable display when the internal signal triggering is
Phase Lock Operation
unstable. It may also be used to slave the analyzer to a
recording device.
The 1st local oscillator can be phase locked to either an
The SLOPE switch selects the positive or negative-going
internal 1 MHz reference oscillator or an external freguency
portion of the triggering signal. The LEVEL control selects
source when it is applied to the EXT REF FREQ IN connector.
Locking the local oscillator to a stable frequency, such as the
the required signal amplitude to trigger the sweep for single
sweep operation.
internal 1 MHz crystal controlled oscillator, reduces the local
oscillator incidental frequency modulation and frequency
drift. This allows narrow dispersion and high resolution set-
tings for signal analysis.
RF Center Frequency Tuning
The frequency range of an external reference frequency
The dial and the analyzer are tuned through the fre-
is 1 MHz to 5 MHz, and amplitude limitations are 1 to 5
quency range of each band by the RF CENTER FREQUENCY
volts peak to peak. The external signal for phase lock
control. The dial frequency calibration is accurate to within
operation is applied to the phase lock circuit when the INT
(2 MHz + 1% of the dial reading) when the FINE RF CEN-
REF FREQ control is turned ccw to the OFF OR EXT REF FREQ
TER FREQ and the IF CENTER FREQ controls are centered.
IN position.
The RF CENTER FREQUENCY control is supplemented by
The LOCK CHECK pushbutton applies the output of the
a FINE RF CENTER FREQ, ten turn control, that provides a
phase lock amplifier to the vertical display system. The out-
fine tuning adjustment through a limited frequency range
put of the phase lock amplifier contains the following: (1)
on either side of the dial frequency, or the RF center fre-
Beat frequency signals between the local oscillator and the
quency. This allows fine tuning when operating on the high
reference frequency when the oscillator frequency is very
frequency scales with narrow dispersion, or fine adjustment
close to a lock with the reference frequency. (2) A DC ref-
to establish a phase lock condition.
2-14
