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AMPTD Y Scale
Example: POW:ATT 20
Dual attenuator configuration: sets the mechanical attenuator to 20 dB
Single attenuator mode: sets the main attenuation to 20 dB (see below for
definition of “main” attenuation).
If the attenuator was in Auto, it sets it to Manual.
Dependencies: Some measurements do not support the Auto setting of
(Mech) Atten. In these
measurements, the Auto/Man selection is not available, and the Auto/Man line
on the key disappears.
In dual attenuator configurations, when the electronic attenuator is enabled,
the mechanical attenuator has no auto setting and the Auto/Man line on the
key disappears. The state of Auto/Man is remembered and restored when the
electronic attenuator is once again disabled. This is described in more detail
in the “Enable Elec Atten” on page 854 key description.
See “Attenuator Configurations and Auto/Man” on page 854 for more
information on the Auto/Man functionality of Attenuation.
Couplings: When
(Mech) Atten is in Auto, it uses the following algorithm to determine a
value:
Atten = ReferenceLevel + PreAmpGain + ExternalGain – RefLevelOffset -
MaxMixerLevel + IF Gain.
Limit this value to be between 6 dB and the Max value. No value below 6 dB
can ever be chosen by Auto.
The resulting value is rounded up to the largest value possible given the
attenuation step setting. That is, 50.01 dB would change to 60 dB (for a 10 dB
attenuation step).
The “IF Gain” term in the equation above is either 0 dB or +10 dB, depending
on the settings of FFT IF Gain, Swept IF Gain, max Ref Level and the
Auto/Man setting of Mech Atten.
In External Mixing and BBIQ,where the Attenuator is not in the signal path,
the Attenuator setting changes as described above when
(Mech) Atten is in
Auto, but no changes are made to the actual attenuator hardware setting until
the input is changed back to the RF Input.
Preset: The preset for Mech Attenuation is “Auto.”
The Auto value of attenuation is:
CXA, EXA, MXA and PXA: 10 dB
EXT: 6dB
State Saved: Saved in instrument state