Manual Mode Operating Instructions 6-3
6.3.1 Input: Attenuator
and preamplifier
Being entered in the Input submenu, to increase or decrease the attenuation
at the input, press Att + or Att -, and for each touch the attenuation is
increased or decreased of 5 dB (preset value). Depressing either one of
these keys force the receiver in manual attenuation.
When the input attenuation is 0dB (condition that can be achieved only if the
Minimum Attenuation is set to 0 dB as well), the yellow led to the left of the
input BNC connector is ON and indicates a warning status.
The Min Att button acts as a toggle switch: it selects or deselects the
minimum attenuation of 10 dB. When the minimum attenuation is selected,
the attenuator – doesn’t matter if in automatic or in manual condition -
cannot be lowered under 10 dB.
Unless specifically required by the test conditions, do not remove the
minimum attenuation of 10 dB.
With the Preamp key it is possible to insert or exclude the built-in low noise
preamplification of 20 dB.
The internal 20 dB preamplifier can be used when very weak signals have to
be investigated. As already mentioned, with the preamplifier ON the receiver
takes automatically care of the 20 dB gain when measuring the signals.
The Att Auto button is used to switch from the two conditions of manual or
automatic attenuation setting.
Please note that the switching of the attenuators is relatively noisy and you
can perceive it distinctly with a “click” for each switch operation.
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.
In case an OVERLOAD indication occurs it is necessary to add an
external attenuator to carry on the measurement without overpassing
the declared limit for continuous power or spectral density.
6.3.2 Misc
Under the Miscellaneous 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.
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.
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