This is gross over-simplification, but it is, sadly, the thinking of the
EMC community and the regulations on EMC.
I've written extensively on this, so won't repeat it here. Here's the
most recent.
http://k9yc.com/KillingReceiveNoise.pdf
And, of course, k9yc.com/RFI-Ham.pdf
VERY little RFI is conducted INTO equipment via the power line. Most RF
trash is conducted out of equipment by "the Pin One Problem" as a common
mode current on cable shields and the power system "green wire." it is
then radiated by that wiring, and ends up on our antennas like any other
radiated signal. This is the mechanism for radiation from CATV systems,
power systems, and nearly all electronics.
RF trash is also radiated by wiring internal to equipment as a result of
poor circuit layout and poor shielding. Both conditions must be present
-- it's entirely practical to build unshielded equipment with no
radiated trash using good circuit layout and construction. This
mechanism is often important with "big" equipment like HVAC systems and
solar systems.
73, Jim K9YC
On 7/19/2017 8:17 AM, Bob McGraw K4TAX wrote:
There's basically two types of RFI.
Conducted --- Being noise/RFI traveling through the wiring thus via
direct connection. Conducted RFI can be attenuated to satisfactory
levels by including a power line filter in the system {preferably at
the source}. The filter suppresses conducted noise leaving the unit,
reducing RFI to acceptable levels. It also helps to lower the
susceptibility of the equipment to incoming power line noise that can
affect its performance
Radiated --- Being noise/RFI via the wiring into the air, i.e.
transmitted. Separation of power and antenna physically is often an
improvement. Radiated RFI is usually controlled by providing proper
shielding in the enclosure of the equipment.
Regarding separate circuits, in most all cases each circuit terminates
into the service panel to which all are then common. The advantage
I've seen with separate circuits is in the distribution of neutral
current. A large unbalance in load between L1 and L2 results in a
differential neutral current. In this case, the IR value will cause
the neutral to be above earth/ground.
Often, figuring out which type and source is the challenge.
73
Bob, K4TAX
On 7/19/2017 9:52 AM, Clay Autery wrote:
Hmmmm.... Jim... I have a variable speed down-hole pump on my water
well... reckon that could cause RFI via the AC wiring?
The down-hole pump is 220VDC on dedicated circuit, and shack is on a
separate dedicated circuit from same service with separate sub-panel.
______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
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