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6.4 RBW
6.5 Hold Time
6.6 Demodulator
The Resolution Bandwidth command is used to select the bandwidth of
the measuring filter. Seven bandwidth filters are available:
• 200 Hz CISPR 16 shaped at -6dB
•
9 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
The three 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 9010 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 9010 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).
Switching ON the built-in AM demodulator, the volume can be adjusted with
the rotating knob, and the level is shown by the black bar on the screen.
The demodulated signals can be heard with headphones or earphones
connected to the front panel of the PMM 9010, or amplified and/or recorded
by any suitable device.
An FM demodulator – or other demodulators - is not available for the time
being in the frequency band covered by the PMM 9010.
Manual Mode Operating Instructions
6-5
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