Noise With Tone (Notched Noise); Principles; How It Is Measured - HP 4934A Operating And Calibration Manual

Noise with Tone (Notched Noise)
Principles
This measurement quantifies total noise which includes background noise
and noise generated only when a signal is present, such as when the circuit
includes compandors and/or quantizers.
RECEIVER
.-•-1 MON'TOF^
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....I spp A<- if; a
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TRANSMIT
How it is Measured
1 The transmitter sends a 1004 Hz holding tone at the nominal data level.
2 The receiver notches out the 1004 Hz holding tone and what is left is measured
via a weighting filter (C-Message, 3 kHz Flat, 15 kHz Flat, Program or 50 kBit).
The measured noise level is displayed in dBm (0 dBm = -90 dBm). When the
C-Message filter is used, the result is in units of dBmC. The notch attenuates all
frequencies in the range 995 Hz to 1025 Hz by at least 50 dB.
FREQUENCY RESPONSE = C-MESSAGE FILTER WITH 1004Hz NOTCH
Making Measurements 2-13