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10.13.4 RBW
10.13.5 Hold Time
The Tracking generator is an internal, high stability and accuracy, 50 Ohm
RF generator ranging from 10 Hz to 50 MHz.
It is 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.
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.
With the PMM 9030 the Tracking On function is not available.
The Resolution Bandwidth command is used to select the bandwidth of
the measuring filter. Seven bandwidth filters are available:
• 120 kHz CISPR 16 shaped at -6dB
•
3 kHz at -3dB
•
10 kHz at -3dB
•
30 kHz at -3dB
• 100 kHz at -3dB
• 300 kHz at -3dB
•
1 MHz at -3dB
The four larger filters are selectable from the first RBW screen, and
pressing the More RBW button it is possible to select all the other filters.
These filters are mathematically modeled using FIR (Finite Impulse
Response) technique and they are exactly as required by the standards.
More filters will be available as an option for specific applications, e.g. to
cover Military Standards requirements, etc.
With the Auto Cispr function, the filter will be automatically selected,
according to CISPR standard, depending on the tuned frequency.
When a non-CISPR filter is selected, the Quasi Peak detector is disabled.
The Hold Time (expressed in milliseconds) represents the time the receiver
uses to "take a snapshot" of the incoming signal and to measure it with the
chosen detector. When selecting a detector, the default hold time value is
automatically loaded, but in some cases this time is not appropriate, e.g.
when the interference signals have a low repetition rate. In this case the
PMM 9030 sees a high input signal and therefore tries to set the proper
attenuation automatically increasing the value or the input attenuators.
However, when the input attenuation is set the signal is gone, so the
receiver lowers the attenuation, but then a new peak arrives, and so on and
so forth.
On the other hand, if the Hold Time is too high the PMM 9030 cannot
properly follow the signals.
In this situation the Hold Time value should be manually set to find a
correct compromise.
To set the Hold Time to the lowest possible value (this value dynamically
depends from the measurement conditions), enter the figure 0; if a value
lower than the allowed is entered, the lowest possible value is automatically
selected.
The max. Hold Time that can be set is 30 sec (30.000 ms).
PMM 9030 Frequency Extension
10-33
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