Amateur ExtraE4C10
What is an advantage of having a variety of receiver bandwidths from which to select?
C
Answer
Receivers, transmitters, and measurements
Type
A
The noise figure of the RF amplifier can be adjusted to match the modulation type, thus increasing receiver sensitivity
B
Receiver power consumption can be reduced when wider bandwidth is not required
C
Receive bandwidth can be set to match the modulation bandwidth, maximizing signal-to-noise ratio and minimizing interference
D
Multiple frequencies can be received simultaneously if desired
Answer Notes
Background noise is distributed evenly across the entire radio spectrum. The wider a receiver's bandwidth, the more total noise it lets through to the audio stages.
By matching the receiver's bandwidth to the exact width of the incoming signal's modulation (for example, using a narrow 500 Hz filter for CW and a wider 2.4 kHz filter for SSB), you capture the entire signal while blocking out as much surrounding noise and adjacent-channel interference as possible. This optimizes the signal-to-noise ratio (SNR).
Using adjustable bandwidth does not change the physical noise figure of the RF amplifier, nor is its purpose to reduce power consumption. It is purely a filtering technique to isolate the desired signal from surrounding RF clutter.
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Which of the following choices is a good reason for selecting a high IF for a superheterodyne HF or VHF communications receiver?
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Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?