Rohde & Schwarz Hameg HM5530, Руководство пользователя

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28
Subject to change without notice
T e s t S i g n a l D i s p l a y
Test Signal Display
Operational hints
Prior to operation of the HM 5530 the section „Safety“ heading this
manual should be carefully studied! The instructions given should be
meticulously followed. No special knowledge is required for operating
this instrument. The front panel layout as well as the concentration on
the essential functions allow easy and effi cient use immediately after
fi rst time operation. However, it is material to observe these hints in
order to benefi t from troublefree operation.
By far the most sensitive and thus vulnerable part of the instrument
is the input stage consisting of the input attenuator, a low pass fi lter,
and the fi rst mixer.
Without any attenuation (0 dB) the following input levels resp. voltages
must not be exceeded: +10 dBm (0.7 V
rms
) AC, ±25 V
DC
. With 10 to 50
dB of atten20 dBm is the limit. Higher levels may destruct the
input stage!
When measuring the output signal of a LISN (line impedance standardi-
zation network) , the input must defi nitely be protected with the HZ560,
otherwise there will be high danger of destruction of the input stage!
Whenever attempting the measurement of still unknown signals, it
should be tested (e.g. with a high frequency scope with 50 ohms input)
whether these are within the maximum input levels specifi ed. In any
case, the measurement should be started by switching the attenuator
to its highest position (50 dB) and selecting the widest span (3000 MHz).
This will, however, not preclude that excessive and possibly destructive
signals are present, these may be outside the instrument’s frequency
range! These would not be displayed but could well overdrive and des-
truct the input stage. Short of destruction any overdrive would create
distortions and spurious signals of all sort.
The frequency range below 100 kHz is not specifi ed, any display of
spectra in this region may not be reliable.
The intensity should not be turned up higher than necessary for easy
readability; any higher setting would not reveal more information nor
uncover any signals buried in the noise. Due to the functional principle
which includes a/d conversion and digital storage like in a DSO, all
details are already present even at low intensity, there is no information
content in the trace intensity as in an analog scope. Too high an intensity
will enlarge the spot size and thus in fact deteriorate the recognition
of details, even with optimum focus adjustment. Also, if the intensity
is set too high, the screen phosphor in the area of the noise band will
burn out too soon.
Due to the functional principle of modern spectrum analyzers, a spec-
tral line will be visible even if the center frequency is set to zero. This
is the case if the frequency of the fi rst local oscillator (1
st
LO) is within
the passband of the fi rst if fi lter. This display is called ”Zero Peak“; it is
caused by (undesired) residual oscillator feedthrough in the fi rst mixer
stage, hence the level of this display differs between instruments which
does not indicate any malfunction.
50 MHz Test signal ON
with marker
50 MHz Test signal,
2
nd
harmonic dis-
tortion with Delta-
Marker
Center Frequency
Graticule Line
Video Bandwidth (RO)
Resolution Bandwidth (RO)
Marker Level (RO
Marker Frequency (RO)
Attenuator und dB/div
Reference Level
Testsignal Output Level (RO)
Sweeptime
Reference Level
Graticule Line
Test signal
Output VIEW B
(Stored Signal)
External
Trigger Input
RF Input
(RO = Readout)