Tektronix 1L40, Инструкция по эксплуатации

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Operating Instructions— Type 1L40
(A )
Sin Y
X
spectrum o f a rectangular RF pulse.
(B) Pulsed RF spectrum w ith some FM. Note the unbalance
o f the sidelobes.
1C) Pulsed RF spectrum w ith severe FM. N ote the frequency
s h ift o f the carrier when it is pulsed and the absence
o f deep lobe minim a.
Fig. 2 -1 8 . Pulse modulated displays.
4. Video detection: (See Spectrum Analyzer Terms.) These
spurious responses are usually no problem if the input
signal strength is below — 30 dBm.
5. Internal: These spurious signals are normally below
2X the noise level for the Type 1L40.
Most spurious responses are easily identified as follows:
IF feedthrough signals w ill not tune across the display.
Image signals tune across the display in the direction that
is opposite to that of the true signal response. In the Type
1140 the true signal response tunes from the left side of
the display to the right as the dial frequency is increased
or the RF CENTER FREQ control is turned clockwise. Their
movement across the dispersion window is coincident with
the frequency change of the dial scale as the RF center
frequency is changed.
Higher order modulation or intermodulation produces
spurii that are tunable, but their rate and amount of move­
ment across the dispersion window, as the RF Center
Frequency is tuned, is not coincident with the dial scale
reading.
Most of the spurious signals described, with the exception
of intermodulation products, can be reduced or eliminated
by the use of external bandpass filters.
APPLICATIONS
These basic applications for the Type 1L40 Spectrum
Analyzer are presented to fam iliarize you with its operation.
Relative Amplitude Measurements
The relative amplitudes between signals are measured as
follows:
1. Center the IF CENTER FREQ controls, then tune the sig­
nal with the lowest amplitude to the center of the screen
with the RF CENTER FREQ control.
2. Adjust the G A IN control so the low amplitude signal
establishes some reference amplitude.
3. Tune the stronger signal to the center of the display.
Add IF attentuation by switching in combinations of IF
ATTEN dB switches, until the stronger signal amplitude de­
creases to the same reference amplitude established in
step 2.
4. The total dB attenuation switched in is the relative
amplitude difference, in dB, between the two compared
signals.
NOTE
For maximum accuracy, the signals should be re f­
erenced and com pared near the same location
on the d is p la y . Tune each signal to the reference
w ith the RF CENTER FREQ c o n tro l.
The IF CENTER FREQ, the DISPERSION-COUPLED
RESOLUTION, the FINE RF CENTER FREQ, and the
Tim e/C m controls should not be changed when
measuring re la tive signal a m p litu d e .
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