[Elecraft] PX3 noise generated on KX3-2M

[David Anderson]

Jim,

Thanks for the correction, of course for "ground" I meant "bond", I didn't refer to "earth" because I don't have one, apart from the mandatory mains safety earth in my shack as it is upstairs and I operate VHF and above only.

I didn't use the term "pin 1 problem"  because it isn't a very descriptive teem unless you know the history of how that term came about which you have been very vocal about popularising, but it is indeed the same problem here, "common " ( have I used the correct term) of PCB not directly BONDED to the outer Metal Case.

I was rather pleased that the solution turned out to be so simple and so effective for me. 

Maybe Elecraft could look into making a factory mod, it isn't difficult or costly.

73 from David GM4JJJ

> On 23 Feb 2016, at 19:37, Jim Brown <jim at audiosystemsgroup.com> wrote:
> 
>> On Tue,2/23/2016 10:26 AM, David Anderson wrote:
>> I wrote about my experience and how better grounding of the DC socket of the PX3 to the chassis reduced the radiated noise.
> 
> David,
> 
> Thanks for posting this. I've been bugging Wayne about these issues for more than ten years, and he still hasn't gotten the message. This is a great example of ignoring what EMC guru Henry Ott calls "the hidden schematic lurking behind the ground symbol," and which is a primary cause of EMC failures (RFI, hum, buzz). In the pro audio world, we call it "the Pin One Problem," whereby cable shields fail to contact the shielding enclosure at the point of entry, but instead go to the circuit board, finally reaching the chassis via a path established by the whim of the PC board layout artist.
> 
> One VERY important correction to your post.  This connection is NOT a "ground" or "earth," it is a BOND between the cable shield and the shielding enclosure. Or in the case of the power connector, between DC- and the shielding enclosure. The significance of this is that without that bond, RF can be coupled to that cable and radiated by simple antenna action. In addition, RF can be coupled from one cable shield to another, and from there to an input circuit.
> 
> A connection to actual EARTH is NOT part of a solution to these problems, proper bonding IS critical to the solution. Neil Muncy, ex-W3WJE (SK) put this quite poetically in the tutorial workshops he did for audio professionals. Neil said, "Buy a six pack of your favorite beer, grab a chair and a set of good binoculars, and sit at the end of the runway of O'Hare (substitute your local airport) and CALL ME COLLECT when you see an aircraft take off trailing a ground wire."
> 
> 73, Jim K9YC
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