10 Questions
What is the term denoted by 'dBrnc' in F1A weighting?
Decibels relative to the reference noise level with C-weighting applied
What is the effect of a +7 test point on a reading of 58 dBrnC on a Western Electric 3A test set?
It increases the reading by 7 decibels
What is the relationship between the readings on the disturbing pair and the disturbed pair in a crosstalk coupling measurement?
The difference between the readings is a measure of the crosstalk coupling
What is the unit of power in the context of signal-to-noise ratio?
Decibel-milliwatt
What is the purpose of F1A weighting in noise measurement?
To apply a specific weighting to the noise measurement
What is the effect of shielding on electromagnetic interference (EMI)?
It decreases the EMI
What is the purpose of filtering in noise suppression?
To attenuate the noise
What is the relationship between the signal-to-noise ratio and the receiver front end design?
The signal-to-noise ratio is affected by the receiver front end design
What is the unit of measurement for noise in a voice channel?
Decibel-A
What is the effect of a +7 test point on a reading of 58 dBrn on a Western Electric 3A test set?
It increases the reading by 7 decibels
Study Notes
Binary Coding Techniques
- Quantization in PCM (Pulse Code Modulation) involves approximating the continuous amplitude of an analog signal into a finite set of discrete levels, introducing quantization noise.
- The more levels used in quantization, the lower the quantization noise, but it cannot be entirely eliminated due to the discrete nature of the representation.
FM Receiver Circuits
- A limiter is a circuit designed to limit or clip the amplitude of the FM signal, suppressing amplitude variations caused by noise.
- The limiting action ensures that the signal remains constant in amplitude, allowing subsequent stages of the receiver to more effectively deal with frequency variations introduced by the FM modulation.
Noise Sources in VHF Marine-Band Receiver
- In a VHF marine-band receiver, the dominant noise source is often the receiver itself, particularly in the front end.
- The receiver front end includes components such as amplifiers, mixers, and filters, contributing to thermal noise and other forms of internal noise.
Signal Strength Measurements
- The term “level” describes the magnitude of a signal relative to a reference point, indicating the strength or intensity of the signal at a particular location compared to a reference level.
Noise Measurements
- dBmc refers to a measurement in decibels with C-weighting applied, often used in industrial and commercial noise assessments where lower-frequency noise components are more relevant.
- F1A weighting, denoted as dBrnc, refers to a specific type of noise measurement with weighting applied.
Decibel Measurements
- Reading a 58 dBrnC on a Western Electric 3A test set at a +7 test point is equal to 51 dBrnc0.
- Reading a 58 dBrn at a +7 test point is equal to 46 dBa0.
- A reading of -50 dBm on the disturbing pair, and -80 on the disturbed pair equals 30 dB of crosstalk coupling.
Power
- Power is the rate at which energy is transferred or the rate at which work is done, defined as the amount of energy transferred or converted per unit time.
Learn about quantization in PCM, including the process of discretizing continuous amplitude signals into finite levels, quantization noise, and its effects.
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