The concept of a so-called "ground loop" is completely false. It has no
basis in physics. The "buzz" we hear when equipment is not properly
bonded consists of triplen harmonics of the mains frequency, 50 or 60
Hz, depending on where you live. What DOES couple this trash is the
failure to follow proper engineering practice, which is to bond together
the chassis of every piece of equipment in a system, to bond all grounds
in a building, and to bond that combination of equipment to the
combination of building grounds. (my friends in the UK substitute the
word "earth" for "ground.") A second important part of good practice is
to get power for all interconnected equipment from mains (power) outlets
that have the same Green Wire (protected earth conductor), or whose
green wires are bonded together.
When all of this done, the station is safe for lightning, and no
"isolation" is needed.
Details of proper practice is at http://k9yc.com/GroundingAndAudio.pdf
73, Jim K9YC
On 8/8/2019 3:43 AM, Paul Randall wrote:
The point of the isolated interface is to prevent noise/hum caused by
ground loops but if there is no ground at all, it is not only useless
but actually causes a big problem. I can only assume that if I saw lots
of 50Hz spurs on receive, there was a good chance they were there on
transmit as well.
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