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Chasing RFI noise in our home


I have been chasing sources of RFI to my station, from systems and devices within our home. It's been very interesting! The biggest villains have proven to be our landline DSL service, our refrigerator, our RING cameras, one of our Z-Wave light switches, our dish washer, our garage door opener and the LED lights **** above the desk of my station.

DSL Service - After identifying the problem, our solution was to end our service with CenturyLink and go with the local Sparklight Cable Internet service. Solved that problem. See the attached photo showing the DSL interference that starts at 3.8 MHz and goes up from there. Seven to eight dB of destruction!

Refrigerator - There are two noise signatures here. One, is a band of interference that repeats about every 57 kHz. It is present nearly all the time, but it is horrific whenever the refrigerator door is opened. The second is a fringe that can be seen on the top of the pan adapter. It repeats about every 3 kHz. It is sometimes there, and sometimes not. Between the various heaters, the compressor, the fans, the lights and all in the refrigerator, there are a lot of waterfall signatures that I see, and I see them change when I hear the sounds from the refrigerator change. By the way, it is about a 9-year old Kenmore.

RING Cameras - We have five RING cameras that are Ethernet PoE connected to our network. They all produce spikes, roughly 250 kHz apart, all the way thru the HF band. Fortunately they are pretty narrow and not as disruptive as they appear, but they are a problem.

Z-Wave light switch - One of five switches of the same manufacturer (Leviton) was "noisy". It generally raised the noise floor about 5 to 8 dB. Interestingly, the interference was far worse when the switch was OFF than when it was ON.

Dish Washer - Most of the impact from the dish washer is below about 3.75 MHz, but it can be quite severe. The signature on the waterfall depends on whether the washer pump is running, or the drying circulation fan, and so forth. The effect is essentially a significant increase in the noise floor.

Garage Door Opener - Fortunately the problem only exists when the motor is running. It raises the noise floor probably 10 to 15 dB and has a spiked waveform that repeats about every 16 kHz. It is a MyQ garage door opener, about six years old. It sounds quite disruptive when it is operating.

LED rope light - This interference is essentially a step up and a decay, then a step up and a decay, about every 75 kHz. There isn't any signature sound to it, just a raise of the noise floor.

This is an extremely abbreviated report on what I learned. But the bottom line is that with dropping the DSL, replacing the Z-Wave switch and running a second ground wire from the refrigerator to the adjacent microwave (that improved it a bunch), my overall noise floor is very much improved.

I've hopefully attached several photos to show the above. The last two should be a BEFORE and an AFTER I made the changes. Most all of the photos are on 80M, as that is where I spend a lot of my time. Note that the noise floor on the BEFORE picture is about -90 dB to -92 dB. In the AFTER photo, it is about -100 dB to -118 dB. That's BIG!!! Just thought I would share my findings. Note on the AFTER photo, the major bands of interference on the left half of the display are the refrigerator. I'm just not sure I can justify $2,000 to $3,500 to replace a refrigerator to make my hobby more user friendly. Rats!


  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭

    I had an LG fridge a few years ago that totally wiped out the 40m band for me. I tried everything -- including AC line filters on the fridge and my rig. They helped a bit, but only turning off the fridge at the circuit breaker really worked. So, I had to 'time' my 40m DX'ing to when the wife wasn't home, and only for about an hour at a time!

    My new locale just seems to be particularly noisy on 40m (s7-8) and 80m (s5-7). It doesn't seem to matter what time of day, so I'm thinking it's just the plethora of LED lights, etc. in the neighbourhood.....

  • K7JV
    K7JV Member ✭✭

    Sorry, I haven't checked back here for a few days. You've got the surefire solution for your "fridge", but one would have to be very careful not to forget something in the process, or the wrath of our wives could be ugly!

    I was astounded by the severity of some of the sources in our home. Particularly, I was astounded by the damage our "fridge" does to me on 80. On the plus, I can change to other antennas and the problem does get somewhat reduced. But all of my antennas are compromise antennas as we live in a development with pretty strict CC&R's. No outside visible antennas are allowed. (Except satellite TV). Also, our home is one of three in a triplex townhome configuration. It is built long and somewhat narrow, so any antennas on frequencies below 30M have to be oriented NW to SE. Not the best for working the US. Probably not bad for your eastern prairie provinces, ON, QC and the maritimes, our upper midwest and the New England part of the US. Oh well, onward and forward, right?

    Cheers and best 73, and good luck with your "searchings" and "fixings".

  • Ken Wells
    Ken Wells Community Manager admin


    The house we bought and moved into in June 2019 has an LG Fridge, LG Gas stove, and LG Dishwasher, all from the same series. (We bought new front-load Samsung Washer and Drier when we got here)

    I get some nasty repeated, traveling "humps" on 40, 80 & 160 Meters with an elevated noise floor.

    I was blaming it on a poorly installed cable TV/Internet wiring. Now I know where to look.

    I thought this place in the country 5 miles north of Lafayette, Indiana would be wonderfully quiet! WRONG!

  • NO1PC
    NO1PC Member ✭✭
    Curious about the construct/configuration of the shack gear... specifically proper ground/bonding?

    I have a mix of all sorts of similar appliances, IoT, a Ring, 99% of lighting is LED, a dozen computers in the shack, over a dozen wall-warts all over, PoE and wireless cameras... not a hint of RF noise affecting the shack from anything consumer or other grade. Had DSL years ago (no issues then), cable now.

    Maybe I'm not buying the 'wrong' products, or even the once mediocre and now more robust ground/bonding just precludes all those worries. (Not about to un-ground all the shack gear to test for this.)
  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    @NO1PC Believe it or not Ground or Bounding has great value, but very little in dealing with local RFI. This is a common misconception with received RF noise.

    All the items that were mentioned all have their own little transmitters in them. Often, they don't have very good construction practices. Odds are you could fix most of these items by finding the power supplies and control boards and adding 0.1uF capacitors all of them. This used to be the practice some time ago.

    However, every extra little expense reduces profit margins if you are a manufacturer. RFI doesn't bother most people and governments don't limit imports for those issues. The EU has better control over it, and, as an example, we had to redesign part of the 6600 to reduce some RF noise leakage before it could be made for sale in the EU.

    Chokes help as well. Chokes on the offending equipment. Chokes on the receiving equipment, etc. The quieter you are, the more you can hear.


  • Stan VA7NF
    Stan VA7NF Member ✭✭✭

    I must disagree slightly with your comments. I have found, over many years, that there are several environments:

    Networking gear (especially designed on cat 5 or lower standards turn the house network (utp cat) into a large antenna. Building network gear to CAT6 standard required all cable connections be through balanced transformers - This at least reduced common mode radiation by driving the cables as a balanced transmission line; still some radiation but much less.

    Powerline sources (wallwarts and direct drive appliance motors) may be helped by adding grounds but household grounds just make an antenna. They need inside the case, or no further away than the power cord, an effective RFI/EMI filter. Many residential powerline plug ins have basic filtering but a metal cased 3 wire (hot/neutral/safety ground) filter is most effective. A very good (for filtering) is a power bar from MFJ (but I had to fix the internal wiring on the first two I purchased; perhaps their build is now better)

    In all those cases the interference is picked up by the antenna if it is near the home, not into a well grounded station by other means. Always important to remember in noise pickup is the ground wire may become part of the antenna.

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