Tektronix 1L40, Instruction Manual

Page: 7 / 145

SECTION
2
OPERATING INSTRUCTIONS
Type 1L40
Change information, if any, affecting this section will be found at the
rear of the manual.
Introduction
This section of the manual presents installation instruc­
tions, a glossary of Spectrum Analyzer terms, a description
and function of the Type 1L40 front panel controls and con­
nectors, a first time operation procedure, and some basic
applications for the analyzer.
Installation
The Type 1L40 is designed to operate in all Tektronix
Oscilloscopes that accept the letter or 1-series plug-in units.
It may also be used with Tektronix Type 132 or Type 133
Plug-In Power Supply units, with the output displayed on
the CRT of any oscilloscope that has a 100 V or 150 V
sweep output available.
Set the Sweep Voltage selector at the rear panel (see
Fig. 2-4) to the required position for the oscilloscope the
analyzer is to be operated with. If the oscilloscope saw­
tooth voltage output is not given on the chart, refer to the
oscilloscope instruction manual.
Insert the Type 1L40 into the plug-in compartment and
fasten the securing latch. Connect a cable or patch cord
between the oscilloscope sweep output and the Type 1L40
L
f.
1 »
> •
if
/
(A ) N ormal response to a cw signal
J
j
/
f
(B) Effeet o f disto rtion c n a cw sign al.
Fig. 2 -1 . (A ) Norm al response to a cw signal. (B) Effect of
disto rtio n on a CW signal.
SWEEP INPUT connector. Turn on the oscilloscope power
and allow approximately 20 minutes wgmum—p filip d for
the instrument to stabilize.
Oscilloscope Modification
If the Type 1L40 is used with early Tektronix Type 541,
541 A, 543, 543A, 545 and 545A oscilloscopes, an undesir­
able display distortion and dispersion non-linearity may
be present. This distortion is caused by a portion of the
vertical output signal from the Vertical Signal Out C. F.
V1223A (V1050B Type 545), feeding into the Spectrum Ana­
lyzer on the +2 2 5 V supply. The distortion appears as a
change of dispersion linearity with a change of the analyzer
G A IN control setting and is most noticeable in the narrow
dispersion setting such as 1 kHz/cm. It also appears as
a non-symmetrical response to a CW signal in which the
slope of one side of the signal drops abruptly to the base
line. See Fig. 2-1.
This condition is corrected by changing the +2 2 5 volt
supply for the Vertical Signal O ut C. F. from the junction
of R1008 and R1007 (R1153 and R1152, Type 545) to the
other side of R1008 (R1153) which is the + 225 V supply.
Fig. 2-2 is a diagram of the circuit involved.
Spectrum Analyzer Terms
The following glossary of spectrum analyzer terms is pre­
sented as an aid to understanding the terms as they are
used in this manual.
Spectrum Analyzer — A device that displays a graph of
the relative power distribution as a function of frequency,
typically on a cathode-ray tube or chart recorder.
Types: Real-time and non real-time.
A real-time spectrum analyzer performs a continous
analysis of the incoming signal, with the time sequence of
events preserved between input and output.
A non-real-time spectrum analyzer performs an analysis
of a repetitive event by a sampling process.
Methods: Swept front end and swept intermediate fre­
quency.
A swept front end spectrum analyzer is a superheterodyne
spectrum analyzer in which the first local oscillator is swept.
A swept IF spectrum analyzer is a superheterodyne spec­
trum analyzer in which a local oscillator other than the
first is swept.
Center frequency (radio frequency or intermediate fre­
quency)— That frequency which corresponds to the center of
the reference coordinate.
2-1