On Fri,4/10/2015 12:44 AM, Steve Ireland wrote:
Isolating mic ground from the rig ground, along with making sure the interface
aluminium box was connected to the rig ground, stopped the RF from getting into
the CM-500 electret element.
Misconception Alert!
We are not talking about a connection to Mother Earth. That is NOT part
of a solution to RFI. What we are talking about is avoiding a path for
RF current flowing on the shield that goes THROUGH the box. When we
connect the shield to the chassis, we keep the RF outside the box.
When we try to "isolate" grounds, we CAUSE problems. That's because
Mother Nature does not read our schematics, but rather looks at what we
have done.
A large part of our problem is what we CALL things. When we call circuit
reference "ground," we somehow come to believe that it infers a
connection to earth. WRONG! The ONLY reason for a connection to earth is
LIGHTNING PROTECTION.
73, Jim K9YC
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