Tektronix 1L20, Инструкция по эксплуатации

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Operating Instructions— Type 1L20
LOG
Fig. 2 -3 . VERTICAL DISPLAY Modes showing a 10 MHz carrier signal
modulated by 10 kHz.
5. If the signal did not move when the RF CENTER FREQ
control was changed, you are watching an IF feedthrough
signal.
MIXER PEAKING Control Operation
The front-panel MIXER PEAKING control has been pro­
vided to improve the over-all sensitivity of the Spectrum
Analyzer on Bands 2-5. (It will have no effect on Band 1
signals.) Its action is quite broad; therefore it can usually
be set at an optimum setting and w ill not need to be
changed unless there is a large change in signal frequency.
As a very rough guide, the MIXER PEAKING control will
be set near the counterclockwise end of its rotation for
Band 2; near the middle of its range for Bands 3 and 4;
and near either end for Band 5.
Phase Lock Operation
The Phase Lock circuit increases the horizontal (frequency)
stability of narrow-dispersion displays by locking the Local
Oscillator in phase with a more stable reference signal.
This reference signal can come from one of two sources
— either the internal crystal-controlled 1 MHz reference
oscillator, or an external 1-5 MHz reference signal applied
to the front-panel REF FREQ IN connector.
The Spectrum Analyzer is set up for phase-locked opera­
tion as follows:
1. Set both IF CENTER FREQ controls to midrange.
2. Center the signal on the graticule with the RF CENTER
FREQ control.
3. Connect the external reference signal, if used, to the
REF FREQ IN connector and set the REF FREQ switch to
the desired reference source.
4. Hold in the LOCK CHECK pushbutton and set the RF
CENTER FREQ and FINE FREQ controls to the closest phase-
locked range. (Figure 2-4 shows the display that results
from depressing the LOCK CHECK pushbutton while turning
the RF CENTER FREQ control through a phase-locked range.
In actual practice, the RF CENTER FREQ control is usually
set to center the desired RF INPUT signal and phase lock
is accomplished by readjusting the FINE FREQ control.)
Under some conditions, small beat signals will appear
between two successive large beats (see Fig. 2-5). These
lock points may be used, but the oscillator may tend to
drop out of lock easier than when locked with the larger
beat signals.
5. Release the LOCK CHECK pushbutton and set the
DISPERSION— COUPLED RESOLUTION switches to the
desired settings. If it is necessary to re-center the signal, use
the IF CENTER FREQ controls; do not move the RF CENTER
FREQ or FINE FREQ controls after the Analyzer is set for
phase lock.
When using DISPERSION settings of lOOkHz/CM or nar­
rower, the desired RF INPUT signal may disappear o ff the
screen when phase lock is lost; a slight adjustment o f the
FINE FREQ control will bring the Analyzer back into a
phase-lock mode and return the signal under observation
to the screen.
2 -5