Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?
The attenuator has a low-pass filter to increase the strength of lower frequency signals
The attenuator has a noise filter to suppress interference
Signals are attenuated separately from the noise
Atmospheric noise is generally greater than internally generated noise even after attenuation✓پاسخ درست
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On the lower HF bands the atmospheric and man-made noise arriving from the antenna is far stronger than the receiver's own noise, so attenuation reduces the wanted signal and that external noise by the same amount and the ratio between them barely changes. Meanwhile the absolute levels reaching the front end drop enough to stop overload.