INTENSIFIER-Controls the relative brightness between the
plays on the CRT that are not tunable with the RF center fre-
displayed signal and the trace baseline.
quency controls.
POSITION-TWO (2) controls that position the CRT beam
2. Image response-The superheterodyne process results
in the vertical and horizontal plane.
in two major IF responses, separated from each other by
twice the IF. The spectrum analyzer is usually calibrated to
only one of these two responses. The other is called the
Time Base Controls
image.
TIME/DIV-Selects calibrated sweep rates from 0.5 s/div to
3. Harmonic conversion-The spectrum analyzer will re-
10 s/div in a 1-2-5 sequence.
spond to signals that mix with harmonics of the local oscil-
lator and produce the intermediate frequency. Most spect-
VARIABLE-Permits an uncalibrated overlapping adjust-
rum analyzers have dials calibrated for some of these higher
ment of the sweep rate so the sweep rate may be varied
order conversions. The uncalibrated conversions are spurious
continuously from 10 s/div to approximately 1.25 s/div.
responses.
4. Intermodulation-in the case of more than one input
Trigger Controls
signal, the myriad of combinations of the sums and differ-
ences of these signals between themselves and their multiples
SLOPE-Selects the positive or negative portion of
the
creates extraneous response known as intermodulation. The
input signal to trigger the time base,
most harmful intermodulation is third order, caused by the
LEVEL-Selects the amplitude point on the triggering sig-
second harmonic of one signal combining with the funda-
nal where sweep triggering occurs. In the fully clockwise
mental of another.
position, the sweep circuit free runs.
5. Video detection-The first mixer will act as a video de-
SOURCE-Selects signal source for triggering the time
tector if sufficient input signal is applied, A narrow pulse
base. Selections are: INT (from vertical amplifier); LINE
may have sufficient energy at the intermediate frequency
to show up as an intermediate frequency feedthrough.
rear panel BNC connector labeled TRIG IN).
6. Internal-A spurious response on the display caused
by a signal generated within the spectrum analyzer that is
Spectrum Analyzer Section (IF)
in no way connected with an external signal.
7. Anomalous IF responses-The filter characteristic of the
DISPERSION RANGE-Selects the range of the DISPER
resolutian-dete rmining amplifier may exhibit extraneous pass-
SION selector.
bands. This results in extraneous spectrum analyzer responses
DISPERSION--Selects the dispersion (frequency width) of
when a signal is being analyzed.
the display in conjunction with the DISPERSION RANGE
8. Zero frequency feedthrough-(zero pip)-The response
switch. Dispersion selections are 10 MHz/div to 1 kHz/div
produced when the first local oscillator frequency is within
in a 1-2-5 sequence plus 0 dispersion position.
the IF passband. This corresponds to zero input frequency
When the DISPERSION selector is in the 0 position, the
and is sometimes not suppressed so as to act as a zero fre-
analyzer functions as a fixed tuned receiver, permitting
quency marker.
displays of the time domain characteristics of modulation
Sweep repetition rate-The number of sweep excursions
within the resolution bandwidth capabilities of the analy-
per unit of time. Approximately the inverse of sweep time
zer.
for a free-running sweep.
COUPLED RESOLUTION-Selects the analyzer resolution
Sweep time-The time required for the spot on the refer-
bandwidth. Eleven selectable ranges from approximately
ence coordinate (frequency in spectrum analyzer) to move
100 kHz to less than 1 kHz are provided. Optimum resolu-
across the graticule, (In a linear spectrum system, sweep
tion for a given dispersion is generally obtained with the
time is Time/Division multiplied by total divisions.)
RESOLUTION control coupled to the DISPERSION selector.
DISPERSION CAL--A screwdriver adjustment to calibrate
the MHz/div dispersion.
CONTROLS AND CONNECTORS
DISPERSION BAL-Adjusted to balance the dispersion cen-
The following is a brief description of the operation or
ter (center freqeuncy point) of the MHz/DIV and kHz/
function of the controls and connectors on the front (see Fig.
DIV positions of the DISPERSION RANGE switch.
later in this section under operating information.
IF ATTENUATOR dB-Series of six toggle switches to pro
vide a range of IF attenuation from 1 dB to 51 dB.
CRT Controls
GAIN-A variable control of the analyzer IF gain.
lNTENSITY-Controls brightness of the CRT trace
IF CENTER FREQ-A 10 turn control that adjusts the IF
SCALE ILLUM-Controls graticule light level.
center frequency of the display. Provides a + and - 10
MHz adjustment in 10 MHz/DIV dispersion position, a +
FOCUS-Adjusts spot size for optimum display definition.
and - 25 MHz adjustment of the center frequency through
the 5 MHz/div to 0.2 MHz/div positions and a + and -
ASTIGMATISM-Used in conjunction with the FOCUS con-
2.5 MHz adjustments through the 500 kHz/div to 1 kHz/div
trol to adjust spot shape and obtain optimum display de-
DISPERSION positions.
finition.
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