[TenTec] On Switching Power Supplies

[Bob McGraw - K4TAX]

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