[RFI] How much RF does your power company deliver along with the AC?
Christopher E. Brown
cbrown at woods.net
Sat Aug 22 18:48:54 PDT 2009
On Sat, 22 Aug 2009, Jim Brown wrote:
> On Sat, 22 Aug 2009 18:22:49 -0500 (CDT), Christopher E. Brown wrote:
>> A small loop near any AC wiring shows strong wideband noise, move a couple
>> feet away and nothing.
> This is with power to you entire building killed? Main breaker? Individual
> What is your power system ground? What is your shack ground? How are they
> connected to each other?
> Another thought -- have you checked your home for bonds between neutral and
> the green wire? Have you checked each outlet for proper wiring?
> Electricians make mistakes. An outlet wired wrong, or an extra
> neutral/ground bond can do lots of mischief.
> Jim K9YC
My work involves (indirectly) alot of power work, so I have a better than
normal understanding of residential AC for a non sparky.
AC entrance is opposite side of the house from the shack, 200 amp service.
Meter base and 2 100 amp shutoff breakers at service. Neutral bond is
here, with a rod electrode and underground water.
>From the disconnect(s) two 4 wire feeders go to 2 breaker panels on
opposite sides of the house. There are no extra neutral bonds, and all
hot/neutral/gnd run together (none of the hot over here, neutral over
there, shared neutral or shared gnd your see in older construction).
Circuits hit multiple outlets, and in a few places there are 3 way
switches or a T where the lighting circuit feeds from the outlet circuit,
but in all cases hot/neu/gnd are run together and hot/return path is in
the same bundle.
All of the plumbing ducting/etc has been checked for AC and DC current.
The 2 breaker panels feed 2 different "zones", each panel handles
neutral/gnd properly for a sub panel, only bond is at the service
entrance. The wired ethernet is choked on every line and only runs
between gear on one of the panels.
The shack is all one circuit including lighting. A #12 run to 4 20amp
outlets and the overhead light, maybe 30 feet total run from the panel to
the first outlet. The entire setup is DC powered (lifeline deepcycle
bank) charged by a IOTA Engineering DLS-55. The computer in the shack is
AC powered from the same circuit as the charger. Network is wireless, the
only other outside connect is the RigBlaster PnP but that is only
connected when in use.
The shack gnd bus is std 1.5x19x.25 inch copper buss bars linked by 1.5
wide .032 thick flashing. RF gnd is driven rod plus about 20 feet of 4in
wide flashing buried 24 - 30 inched deep. #4 solid bare Cu runs about
50 - 60 feed from the RF rod to the AC rod, buried deep enough to count
as an electrode on its own.
The ONLY conductive path from the shack to the AC ground is the #4
The charger and its case connect to the AC ground, but the charger output
ground is isolated at DC and choked on both sides.
In any event, the noise is present with the charger unplugged, no change
with the RF to AC bind lifted and the shack otherwise totally isolated
(and everything in the house unplugged), and it I get more noise when I
lift the strap from the shack gnd bus to the RF ground.
One of the first things I did here was examing the entire AC system
looking for improper bonding, shared neutrals other any other causes of
unbalanced current flow. Even borrowed a 3 axis gaussmeter to check for
the 60hz mag fields imbalanced flows or extra bonds cause where I could
not visually inspect.
None of this is strongly radiated, as a cross check I used the jeep to
check (102 whip fed through SGC-237 and FT-450). Backed up right to the
house I get the elevated noise floor across the band (mainly looking at
20M here, because it has the least radiated noise outside of a few known
sources but wideband noise is there everywhere 20M and down). Pull out 10
- 50 feet and (on the short whip) it goes away. Back into a neighbors
driveway 4 houses down and get close to the house and same effect (though
it was harder to tell as this also brought be close to their home
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