Many 10 to 20 year old solid state SWL receivers use discreet logic
ICs and
suffer from insufficient bypassing.

I found that bypassing all of the ICs in the R2000 lowered the
internal noise floor
by slightly over 4dB. I measured this degree of improvement on 4
R2000s.

I used 0.001 across the DIPs and 0.001 with a 1uF tantalum across the
LSI chips.
I also added 1uFs willy nilly on the +5V rail.

Terry