A few weeks ago during a discussion of switching power supply and related
noise, I made a comment that the charger for my laptop computer did cause
noise.
Subsequently I did find need to replace that charger with a new one. In
comparing the two, one makes noise and one does not make noise. Now the
interesting observations, both were made in China, both have the exact same
rating, both have the exact same symbols for certification.
However, what's observed different is this;
(a) The one that does create noise has the following statement; "(1) This
device may not cause harmful interference."
(b) The one that does not create noise has the following statement; "(1) This
device will not cause harmful interference."
Now the way I interpret those two statements is statement (a) "may not" can be
also presumed to mean that it may or may not cause harmful interference where
as statement (b) is firm in that it uses the words "will not" is much more
definitive and restrictive.
Apparently there is something to the different "certifications" as earlier
identified, and the results of same. In my case the one marked "WILL NOT" does
not cause any RFI issues or noise issues with the HF reception.
73
Bob, K4TAX
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