Hi Jim,
You might want to consider a combination of chokes that W6GJB built
based on my design for use on our 2000i generator for county
activations. It's two chokes in series, each wound on a2.4-in o.d. #31
cores with #12 Romex (black, white, bare). One is 8 turns on one core,
the other is 8 turns on two cores. Depending on how your oven is wired,
that may be enough conductors, but it if it uses neutral, you'll need
four wires.
A solution I'm planning to build for my standby generator at home, which
is 240 with a neutral, is to twist four conductors of #12 teflon using a
drill motor to produce twisted quad, and to use it to wind the same two
chokes. #12 teflon is preferred for three very important reasons -- it's
stranded silver-coated copper, so lower resistance and VERY flexible,
and the insulation is much less thick than THHN. The flexibility makes
winding much easier, and the diameter makes it possible to fit more more
turns on the cores.
Before you do this, I suggest that you stick a clamp-on ammeter on one
of the phase conductors when the oven is running so that you know the
load for the choke. #12 copper is rated for 20A, and I suspect the
silver-copper would be even better. To minimize any issues with
dissipation, I would NOT put these chokes in an enclosure. Most noise
like this on the ham bands is radiated as a common mode signal on AC
wiring, and it is this component of the noise that the choke kills.
BTW -- it's likely that the noise is generated by either a switching
power supply for the control panel or by a microprocessor in the panel.
See http://k9yc.com/KillingReceiveNoise.pdf for advice on how to tell
the difference between the two sources.
73, Jim K9YC
On 11/29/2018 11:38 AM, Jim Miller wrote:
After doing a whole house shutdown I've identified our LG electric range
(LDE3017ST) as the culprit producing strong RFI on 80m across the whole
band. My antennas are 100ft or more away from the house so this isn't
subtle. This is not causing a similar pattern on 160m.
This range was produced in 2013 and came with the house we recently
purchased. It has a touch panel which likely is the source of the problem.
I'll need to have my wife play with the "buttons" while I'm listening to
see if there is anything obvious.
Short term cure is to flip the breaker in the electric service panel when
operating on 80m unless there is a kit for RFI. I'm not going to attempt a
home-brew repair on something like this.
As expected calls to LG haven't produced any useful response yet. If they
come up with a kit I'll report. We're planning a complete kitchen remodel
so this range won't last more than 6 months anyway.
Picture attached but may not make it thru the list. The strong ocean waves
every 200khz or so are from the range. The finer grained stuff isn't coming
from our house and will require some DF work. I've sent the pic to Dave,
NK7Z for his compendium.
EDIT: I've since discovered that an alternative to switching power at the
breaker panel is to turn on the bottom oven. The result of doing so
completely knocks down the RFI signature. The upper over has some effect,
burners seem to have no effect.
73
jim ab3cv
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