[Elecraft] Hum on KPA1500

[Clay Autery]

NO "water pipe" should ever be used as a service ground...  I thought 
the code was changed to actually bar that practice entirely.

______________________
Clay Autery, KY5G
(318) 518-1389

On 04/05/20 23:06, David Christ wrote:
> That I understand but if the ground from the entrance breaker panel to a water pipe from the street is 30 feet long, can it radiate interference to AM radios near it (both AC and battery powered)?  If so could it cause RFI at even higher frequencies?
>
> David K0LUM
>
>> On Apr 5, 2020, at 10:35 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
>>
>> On 4/5/2020 5:16 PM, Frank O'Donnell wrote:
>>> I'm not the OP, but can you remind us what buzz (multiple harmonics of 60 Hz) might signify?
>> 60 Hz hum is nearly always magnetic coupling in some form; buzz is generated in the three phase power systems used to distribute power. While few of us have 3-phase power in our homes, the systems out on the street ARE 3-phase. These harmonics are present because a very large fraction of the loads on the power system are some form of rectifier-capacitor-input power supply; most of the AC load current flows at the positive and negative peaks of the 60 Hz sine wave to recharge the filter cap.  This causes the current waveform to be a series of positive and negative pulses, and the IR drop causes the top of the voltage waveform to be rounded off. And we know that any distorted signal is composed of harmonics.
>>
>> In an ideally balanced three-phase system with only sine-wave loads, the neutral current goes to zero. But when harmonics are present (the distortion), harmonics whose number is divisible by 3 ADD in the neutral rather than cancel. They also add in the ground!
>>
>> Buzz is generated by leakage current in the power system; it can couple into our equipment by a couple of mechanisms. It can be eliminated by 1) proper bonding within our home and station; and 2) getting power for all station equipment, including computers and other accessories, from the same AC outlet, or from outlets whose green wires are bonded together. All of this is addressed in the slide deck for tutorial talks I've done at Pacificon, Visalia, and to several ham clubs.
>>
>> http://k9yc.com/GroundingAndAudio.pdf
>>
>> 73, Jim K9YC