Operating instructions

LOCAL OPERATION
3-59
Tracking generator facility
The tracking generator facility uses the RF generator of the Service Monitor to provide a tracking
signal source.
This allows the spectrum analyzer to show the frequency response of frequency dependent circuits
such as filters.
The frequency response of any circuit connected between the tracking generator output and the
spectrum analyzer input will be displayed.
When making calculations relating to frequency response results, take into account the
impedance matching between the circuit and the Service Monitor. (See performance
specification.)
The frequency offset facility adds to the above capability by allowing tests to be made to
frequency shifting circuits. The tracking generator’s sweep may be positively or negatively offset
with respect to the spectrum analyzer’s output. The sum of the offset and the frequency analyzer
span, cannot produce a figure beyond the frequency range of the RF generator (see performance
specification). Under these circumstances, the 2948 selects an appropriate span.
Because the RF generator is used as the tracking generator, control is required over both modes of
its operation. The RF generator On/Off menu allows this to be enabled or disabled from the
SPEC ANA mode.
Setting the tracking generator
Control of the tracking generator parameters is carried out from the menu accessed by pressing the
[Track/RF Gen] key. This key will either give direct access to the tracking generator parameters
or to the RF generator On/Off menu, whichever was used last. If the RF generator On/Off menu is
reached, pressing the [Track Gen] key will display the tracking generator parameter control menu
shown in fold out diagram (6-5). This menu gives the following options:-
Tracking generator
ON or OFF.
Alternate presses of the [T/Gen On/Off] key will toggle the tracking generator output
ON
and
OFF. When in the ON condition, the RF level and frequency offset will be shown on the
display.
Tracking generator level.
Pressing the [Level] key will highlight the
Track Gen Level legend and allow the level to
be altered, either by the variable control or by entering a new value using the data entry
keys.
Locking tracking generator frequency to sweep frequency.
Pressing the [Freq Locked] key will lock the Frequency of the tracking generator to the
sweep oscillator of the spectrum analyzer. When locked, the legend
Locked is shown under
the
Offset legend on the display. Repeated presses of this key will toggle between Locked,
(zero offset), and the offset previously set (see below).
Setting the value of the tracking generator frequency offset.
A new value is entered by first pressing the [Freq Offset] key and then using the data entry
keys.
Additionally, the RF generator may be disabled from the spectrum analyzer tracking generator
menu. Pressing the [RF Gen] key will display the RF Generator On/Off menu. Repeated presses
of the [RF Gen On/Off] key will display the
RF Gen Off or the RF Gen On legend. This indicates the
state of the RF generator when the tracking generator facility is off.