L3 NARDA PMM 9010 User Manual page 32

4.2.2.2 Misc
4.2.2.2.1 Tracking
generator
4-4 Sweep Mode Operating Instructions
Under the Miscellanea functions menu it is possible to activate or exclude
the Preselector filters, the Pulse Limiter, and also to enter in the Tracking
generator menu pressing the RF OUT button.
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.
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.
The tracking generator is an internal, high stability and accuracy, 50 Ohm
RF generator ranging from 10 Hz to 50 MHz.
Activating the Tracking On function the generator is always tuned at the
same PMM 9010 measurement frequency and scans the range together with
the receiver. This is the standard way a tracking generator works in all
spectrum analyzers.
If the Tracking On function is disabled, the generator becomes a CW signal
source tuned at the frequency set under the RF OUT Freq window.
As usual, to set a given frequency it is therefore enough to edit the value with
the soft keys and the left an right arrows, confirming the selections entering
the units value (kHz, MHz or GHz).
Pressing 0 as the first figure the decimal dot appears automatically.
In both operating modes (tracking or fixed frequency) the output level can be
set between 60,0 and 90,0 dBµV with 0,1dB steps using the RF OUT Level
button.
If a higher or lower level is needed, the User shall adopt either an external
amplifier or an external attenuator.
The tracking generator is extremely useful for several applications: first of all
it is essential to calibrate the receiver itself thanks to the automatic internal
routines specifically developed to this extent, then it can also be used to
transform the PMM 9010 in a scalar network analyzer, helping a lot in
designing and testing RF filters, active stages and a lot of other circuits.
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