PMM 9030/9060/9180 Frequency Extension 11-51
11.17.3.1 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) up to the max
attenuation available of 55 dB.
Depressing either one of these keys force the receiver in manual
attenuation.
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 10 dB.
The internal 10 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 10 dB gain when measuring the
signals.
The Preamplifier must be mandatory switched off (default) while carrying
on CISPR measurements.
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 9030/9060/9180 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 9030/9060/9180 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.
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