L3 NARDA PMM 9010 User Manual page 40

5.4.2 OVER RANGE
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5.4.3 Misc
5-4 Analyzer Mode Operating Instructions
Using 0 dB attenuation PMM 9010 has no input protection.
This is a potentially dangerous condition for the input stage of the
receiver.
Use 0 dB attenuation only if you are very sure that your input signal is
less than 1 V (or 120 dBµV).
Before to apply an unknown signal to PMM 9010 receiver, use an
oscilloscope or a wide band RF voltmeter to measure it. In any case set
Min. ATT at 10 dB and select the maximum available attenuation with
preamplifier OFF.
If needed, add an external coaxial attenuator on the input signal line.
An Over Range indication will automatically appear on the screen to inform
the User that the levels of the measured signals in the spectrum window is
too high: to avoid measuring errors and even damages to the receiver a
higher attenuation shall be set.
Under the Miscellanea functions menu it is possible to activate or exclude
the Preselector filters, the Pulse Limiter, and also to set the Tracking
Generator.
The Preselector is composed by a group of filters automatically selected by
the PMM 9010 while it is sweeping or anyway measuring. The aim of the
preselector is to reduce the amount of out-of-band energy entering in the
receiver, thus helping a lot in reducing intermodulation problems and similar
undesired behaviors.
In Analyzer mode the preselector is available only if the entire span falls in
one filter band (see the main specification in chapter 1 to verify the frequency
bands). In this situation on the display it will be shown: Preselector ON. If the
span is larger then one filter only, on the display the symbol *** will appear
instead.
It can be set either ON or OFF with the associated button, and normally it
should be always enabled.
On the top left corner of the screen the symbol "Off" or "On" will be displayed.
The Pulse Limiter is a very useful device to protect the input of the receiver
from transient overvoltages. Doing conducted emission tests, quite often
there are conducted disturbances (usually associated to switching operations
in the EUT or along the line under test) which are too high and that
propagates through the LISN up to the receiver. Sometime these
disturbances cannot be seen on the receiver because they are out of
measurement bandwidth, nevertheless the associate energy is high enough
to damage the input attenuator and/or the Analog-to-Digital Converter of the
PMM 9010 (the first mixer in a traditional receiver).
This pulse limiter has an integrated 10dB attenuator and a 30 MHz low-pass
filter.
When the Pulse Limiter is selected, on the upper part of the screen the
letters P.L. appear next the value of the Minimum Attenuation and the
reading on the receiver is automatically corrected for the attenuation factor of
the Pulse Limiter.
Pressing the RF OUT button the receiver enters the Tracking generator
menu.