Amateur Extra › E4 Amateur Practices › E4C11
E4C11
Why does input attenuation reduce receiver overload on the lower frequency HF bands with little or no impact on signal-to-noise ratio?
Pick an answer to check it.
Answer: D. Atmospheric noise is generally greater than internally generated noise even after attenuation
On the low HF bands, atmospheric noise is much stronger than the receiver's own noise. An attenuator lowers signals and atmospheric noise together, so S/N stays about the same while overload is reduced.
Tip: Low bands: band noise dominates anyway.