On 12/31/2023 12:52 PM, Wayne, W0ZW wrote:
As many have suggested, my test set-up was suspect due to a possible
ground loop. I repeated the test with a 3-prong to 2-prong adapter on
the scope power plug to make its chassis floating. Interestingly, the
60 Hz ripple was still present on the measured signal!
Wayne,
Removing the grounding pin is both dangerous and illegal. There is no
such thing as a "ground loop" -- both by LAW and good engineering
practice, all grounds MUST be bonded together. Problems blamed on
so-called ground loops are actually the result of failure to do proper
bonding.
Study N0AX's ARRL book on the topic, to which I contributed, W6RMK's
chapter in the ARRL Handbook, which he contributed around 2011, and/or
the slide deck for tutorial talks I've done at Visalia, Pacificon, and
to several clubs.
http://k9yc.com/GroundingAndAudio.pdf
A common cause of hum and buzz in systems is getting mains power from
outlets on different branch circuits. The cure is simple -- bond the
green wires (or steel backboxes) together in the shack. There must also
be a common point AT THE OPERATING DESK of every chassis that is part of
the station, including computers if they're connected to station
equipment. My slide deck shows how to do this for most computers,
including laptops.
73, Jim K9YC
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