[Elecraft] PX3 Spike won't go away

[Jim Brown]

On Thu,6/23/2016 7:16 PM, Brian Waterworth wrote:
> For some context on why I went to a common point.  I read, what I thought
> was an excellent article, about ground loops from the Flexradio site a
> couple of years ago.  Here is the link:
> http://kc.flex-radio.com/knowledgebasearticle50426.aspx
>
> I thought that daisy chaining would introduce ground loops and hence the
> reason I went to a common point.
Look at your equipment -- there is already a "daisy-chained" loop 
between equipment in the form of those audio cables and coax. The 
problem, as Don notes, is that they often don't go to the chassis, but 
rather to the circuit board, which couples hum, buzz, and RFI into and 
out of equipment. This is "The Pin One Problem," first identified by pro 
audio engineer Neil Muncy (W3WJE, SK) in 1994. Virtually all ham gear, 
including Flex and Elecraft, has Pin One Problems at audio and control 
connectors.

> However, I don't think you are advising this.

Brian,

Study my slides that Don referenced. The concept of a "ground loop" as a 
cause of hum, buzz, and RFI is false, and causes people to do the WRONG 
things to solve such problems. The slides show the TRUE cause, which is 
leakage current from the AC power system.

The ONLY way in which a "loop" is problematic is that it provides a path 
for magnetic coupling between victim equipment and a strong magnetic 
field produced by a noise source. Two common sources are 1) the stray 
fields produced by big power transformers, and 2) a wiring error in home 
power wiring called a "double-bonded neutral," where the neutral is 
bonded to the green wire somewhere other than the point where power 
enters the building. In both cases, the interference is heard as HUM 
(pure 60 Hz) rather than BUZZ (harmonics of 60 Hz).

73, Jim K9YC