AdvancedA-003-003-006
The dial calibration on the output attenuator of a signal generator:
D
Answer
Transmitters and receivers
Type
A
always reads the true output of the signal generator
B
reads half the true output when the attenuator is properly terminated
C
reads twice the true output when the attenuator is properly terminated
D
reads accurately only when the attenuator is properly terminated
Answer Notes
An RF signal generator is typically designed to operate into a specific, purely resistive load impedance, most commonly 50 ohms. The output attenuator dial is calibrated by the manufacturer based on the assumption that this expected load is perfectly matched at the output terminals.
If the attenuator is not properly terminated—for example, if it is connected to a mismatched load, left open, or shorted—the actual voltage delivered to the load will differ significantly from the dial reading. This is due to impedance mismatch causing reflections and standing waves.
Therefore, to guarantee that the signal amplitude accurately matches what is shown on the dial, the device under test must provide the proper matching termination impedance to the generator.
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