RF Noise Floor Concerns From Both Sides Of The Atlantic

Our feed is full of stories about the RF noise floor today, and with good reason. The ARRL reports on the International Amateur Radio Union Region 1 president, [Don Beattie, G3BJ] warning that in densely populated parts of Europe there is a danger that parts of the RF spectrum have become so swamped with noise as to be rendered unusable, while on the other side of the Atlantic we have RadioWorld reporting on similar problems facing AM broadcasting in the USA.

At issue are the usual suspects, interference from poorly shielded or suppressed domestic electronic devices, VDSL broadband, power-over-Ethernet, solar and wind power systems, and a host of other RF-spewing electronics. The combined emissions from all these sources have raised the noise level at some frequencies to the point at which it conceals all but the strongest signals. Any radio amateur will tell you that a station in a rural location will be electrically much quieter than one in a city, it seems that this effect has now reached a crescendo.

In the RadioWorld article, the author [Tom F. King] and his collaborator [Jack Sellmeyer] detail a series of tests they performed on a selection of lighting products from a quality brand, bought at a local Home Depot store. They were gathering data for a submission to the FCC enquiry on the noise floor issue we reported on last year. What they found was unsurprising, significant emissions from all the products they tested. They make some stiff recommendations to the FCC and other bodies concerned with radio spectrum to get tough with offending devices, to stay on top of future developments, and for operators of AM stations to pursue sources of interference.

It could be that there is so much equipment contributing to the noise floor that this battle is lost, but it doesn’t have to be this way. Anyone who has had to prepare a product to pass a properly carried out EMC test will tell you that the requirements are stringent, and it is thus obvious that many manufacturers are shipping products unworthy of the certification they display. It is to be hoped that the authorities will begin to take it seriously before it becomes an order of magnitude worse.

Compliance label image, Moppet65535 [CC BY-SA 3.0].

48 thoughts on “RF Noise Floor Concerns From Both Sides Of The Atlantic

  1. Problem is no one shields anything anymore these days. Rip open multiple plastic encased consumer goods and there is zero shielding, In most cases if there is shielding it is there to keep outside sources from interfering with the device. If they can get away with building something that doesn’t need the shielding to protect from external sources, they don’t seem to give a s**t about what they are spewing out.

    1. Depends what you build, and where it is going to be used.
      Some equipment EMI standards will fail items that pass all FCC/CE consumer goods guidelines.

      Shielding will not necessarily solve your noise/leakage problems, and you can expect most high frequency equipment will need filters on most lines. Most modern equipment use LVDS (much lower bus voltages), and multi-layer PCB with unbroken ground pours. However, parts doing digital synthesis without a bandpass filter, missing a heat-sink on a design that assumes there will be one, and or violating trace impedance rules for the design… will surely create many harmonics that can inject noise in an unpredictable manner. This part of production is not for savvy folks with a weak constitution, or a fear of edge case physics. ;-)

      Regarding the article:
      I suspect these complaints are from users with older 2.4GHz only WiFi equipment that had very limited channel allotment in the user broadcast radius (easily max out at about 170 APs per block..), China/US/Korean/Japan devices auto-selecting prohibited ISM bands in Europe, or some kid doing a blanket de-auth. i.e. little to do with the background noise floor itself…

      One of our esteemed colleagues is likely already triangulating the problem’s origin.

      1. The problem isn’t just on 2.4GHz. Everything from VHF and down is all but unusable in cities because of crappy consumer electronics. There are local signal sources I can listen to with perfect clarity during the early afternoon that gradually become washed out with noise as the evening progresses (as people get home from work/school). I’m talking about signals on the bands used by local fire and police. I suppose it might be important for them to be able to hear dispatch. They are but a few users among thousands of those parts of the spectrum.

  2. CFLs seem to be one of the worst offenders. Un-shielded, almost every one of them.
    The LED lamps I purchased seem to be okay, but I won’t buy any of the WiFi/Bluetooth/speaker ones.

      1. About 20 years ago:
        I once had a Harmon Kardon receiver that was (apparently) triggered by the output from a halogen bulb, on a dimmer circuit.
        This did not happen with “standard” incandescent lamps.
        What happened was at lower settings for the light dimmer and a halogen bulb.
        If I had the stereo cranked up enough to cause that little bit of pulsing sag in the lights
        (kind of the redneck disco effect!)
        A large drum and sharp base note (round wound strings) was prone to flipping the receiver into standby mode.
        IF I raised the brightness of the dimmer above said range, the problem went away.
        Changing back to the standard bulbs would also make it go away and not happen at ANY brightness setting.

        Was a bit strange to figure it out. Just a fair bit of swapping every bulb in my spares box and repeating said musical passage, etc…
        Even hung a couple different pieces of colored plastic, to see if that helped.
        Tried a couple of different sorts of powerline filters that I had on hand….
        Nothing worked.

        Ended up with an Onkyo in place of the HK.

        1. “If I had the stereo cranked up enough to cause that little bit of pulsing sag in the lights
          (kind of the redneck disco effect!)”

          LOL, seen that right before smoke came out of the speakers…

    1. Simple yet very complex, intermodulation from ripple generated by the DC power supply would be one of the major factors. As far as POE goes, all their power supplies are (or should be) switch mode PSUs. These PSUs use high frequency to generate DC voltage efficiently; of which must be filtered out as best as possible. Most wall warts these days are designed with their physical footprint being of utmost importance, so filtering and shielding are not given the care and attention that may be needed. In most cases you will see very basic filtering done to get DC “clean enough” for use. On the other hand commercial products will almost certainly better filtering than your typical wall wart; but even then if you go too cheap or stray from trusted brands you may find that the difference isn’t that great.

    2. It only looks like DC if you watch from far away.
      But there is definately some DC/DC conversions happening at the source and sink to match voltages. And on top of that, you have some HF ethernet communication signals that are easily coupling into the supply path too.
      The emissions from DC/DC converters usually show up more in the conducted emission testing (9kHz to 30MHz), but they can produce emission even at the 6th to 10th multiple of the base converter frequency if you have spectral gaps in the filters or you are otherwise unlucky.
      Spend a few days in a lab trying to get a device to comply with IEC 61000-4 industrial standards in radiated and conducted HF emissions, and you will quickly stop thinking of any DC supply to be pure DC without any AC spectrum hidden inside…

    3. Because the “DC” injected in to the long often unshielded ethernet cable is usually done with SMPS power supplies. For example Cisco PoE injectors are well known to be electrically noisy and thus unusable for anything by radioamateurs who like operating below 30MHz.
      Noisy power supplies feeding long antennas, what could possibly go wrong?

  3. I notified the FCC of a nasty AM band interference issue near a store. Their sole response was to call the power company to come wash off the insulators nearby, which did nothing. Maybe we have a problem because the people in charge of the spectrum won’t do their damned jobs.

  4. Perhaps it’s to do with the trend in society away from low frequency RF (HF and now VHF) to higher bands (UHF and above). Communications devices used to be CB and walkie-talkie. Now it is all smart phones. AM radio is almost dead, and FM is starting to follow. It’s all streamed onto your phone now, and the service providers love it! They’ll *very* happily charge you for something you once got for free!

    Most of the interference / noise floor raising seems to be low frequency stuff (under 500MHz), and if it doesn’t affect your TV reception, mobile phone or in-car sat-nav, nobody seems to care.

    Society is about the needs (actually it is not needs, just wants) of the majority.

    1. Sounds like digital V. analogue transmission to me. Digital transmission (so I understand) isn’t as susceptible to signal degridation as an analogue transmission. IE,

      1. You are joking of course?

        Digital suffers from instant degradation,wheras analog doesn’t. A digital signal is perfect up until that minisule threshold where *nothing* is recoverable. I can still hear & see an analog transmission below the noise floor. Uncomfortable, but doable. No so with digital.

    1. Solar or wind can’t function without some kind of inverter, coal can…(not that it nescessarily doesn’t use any inverters, since the ability to regulate pump speeds is very convenient)

      1. Well, they can, but in the quest for efficiency they aren’t. Solar (PV) generates DC,and to convert to AC an inverter is used. If efficiency (and cost) were degraded and RF emissions prioritized, rotary converters (ie: motor-generator) sets would be used. Hell, even go so far as to use the DC to heat water to steam and drive the same turbine that a coal station uses.

        And of course you could do the same with other solar (thermal electric) as well as wind.

  5. I thought that spread spectrum as a way of cheating would lead to problems, because it allows a device to radiate more and in more frequencies. As opposed to a device that tried operating at a single frequency and be better shielded.

  6. My HF ham gear sits at home unused because of this. Background noise is at 5/9+. The most effective antenna for my situation is a DIY magloop for 20m, I can sometimes null out (well down to 5/8) the very worst of the noise.
    I have had most success battling the noise with JT-65 and various forms of PSK.
    Noise sources appear to be: vDSL, Power line networking gear, and next doors Plasma TV :| . I still get significant vDSL noise up in 2m band.
    The best way around this is to simply go mobile / portable.

        1. Same here. Recently moved to a 60 unit apartment building (family’s needs come ahead of my hobbies) and HF is so unusable that I ended up selling my HF gear. Even VHF is blasted with RFI after the local kids get home from school, making hearing distant repeaters next to impossible.

    1. Sounds just like here, noise S9+ constantly. Even gets into 2m+. For ANY chance at operating, we pray for power failures. Just FWIW, over 250 WIFI devices detected here and cable leakage is horrific, before the switch to digital, one was able to listen to TV shows with a receiver. Do something about it, heh. Replacing 1980s RG-59 in the entire building? Sure, yeah, right….

    2. Same here, S9 noise almost all the time.

      I happen to have a fancy USB Spectrum Analyzer and one day the power in our neighborhood went out, so I started recording everything from 0-20MHz and waited until the power came back on. You can see in the link, power is off on the top 2/3rds of the image, then it comes back on…..

  7. Adding to the list of offenders…

    High efficiency furnaces.

    Solar panel inverters.

    It seems that in the quest to make affordable energy savings, companies cut every corner possible to make them “appear” affordable. But considering the poor engineering and subsidies someone is getting fleeced…

    1. Can’t ignore that…

      I’m working for one of the bigger players in PV and you can make perfectly “silent” (RF wise) inverters up to high kVA levels.

      The same is true for VFDs (in you air-con), induction cooking, …

      As mentioned above, the problem is not that you cannot do that, the problem is that nobody takes the bad-guys from the market…

      1. The problem is probably that nobody (well, maybe except HAM) is willing to pay for high-quality, good shielded/filtered stuff today… And as long as cheap stuff is on the market it’s not difficult to tell what people will buy. Oh and also the majority of people probably have no clue what “RF” is, so… I think David is right: As long as people can use their wifi and stuff like this (on relatively high frequencies) they won’t care. :-(

  8. “…and for operators of AM stations to pursue sources of interference….” When did that become their job?
    “…They make some stiff recommendations to the FCC…” Don’t expect stiff–or any–results.
    “…Anyone who has had to prepare a product to pass a properly carried out EMC test will tell you that the requirements are stringent…It is to be hoped that the authorities will begin to take it seriously before it becomes an order of magnitude worse.” …Creating stiff tests is the SUM TOTAL activity of the FCC.
    From the readers:
    “…I notified the FCC of a nasty AM band interference issue near a store. Their sole response…Maybe we have a problem because the people in charge of the spectrum won’t do their damned jobs…”
    “…My HF ham gear sits at home unused because of this…”
    “…Cant force the neighbors to…remove noisy equipment. 80m is S9+ noise all day everyday.”

    Sorry, Jenny, this is a report on a societal problem; not a technology problem, and it’s not going to get fixed; not in the USA, at any rate, and probably nowhere else.
    Problem is, no one now cares. The FCC’s activity can be summarized as “a carbon copy of most US lawmaking”: pass a lot of laws strictly for ‘show’, forget enforcement.
    It used to be the case that incurring the wrath of the FCC was as bad as toying with the IRS. The FCC would show up at your door if a neighbor complained of your child’s ham radio activity. Not any more. The “…operators of AM stations…” USED TO HAVE the FCC pursue “…sources of interference…” –not for a LONG time, now.
    I can remember the FCC’s patrolling the highways during the C-B Radio boom days, and stopping the jerks who were violating the FCC’s rules. Good luck getting that kind of FCC action, now, on any violation. Violations are now handled by front-end testing, and stern front-end warnings. That oughta do it.

    I’ll stop the rant. I simply think that, given the way things are progressing, King’s and Sellmeyer’s venture is purely quixotic; the genie is out of the bottle. Has been for a long, long time.

    Good try on your part.

    1. “Sorry, Jenny, this is a report on a societal problem; not a technology problem, and it’s not going to get fixed; not in the USA, at any rate, and probably nowhere else.”

      The problem with slippery slopes is it’s hell trying to push the rock back uphill. The problem is a manifestation of neglect (shouldn’t have let things snowball), and too much of one thing (interfering products), and not enough of the other (not enough enforcers to go around).

      1. How could I be so obtuse as to miss “…a page from the ARRL…”?
        I apologise in advance for having to disabuse you of whatever prejudices you have on this subject, but this is exactly the type of rationale which would be used by the FCC to prove that they are really solving the problem, and have been for years.
        You need to try with someone else. And in front of all these highly intelligent, critical-thinking HackaDay readers, too. Not a smooth move. (FYI: this “page from the ARRL” does not prove anything…)
        By the way, where do you work?

  9. I live in Indonesia (highly populated city). Indonesia BANNED filament light bulbs some years ago for residential use. Now my ability to listen to LF and HF radio is GONE. Almost ALL the lamps sold here come out of China, and they are HORRIBLE when it comes to noise (not to mention they FAIL more often than the old incandescent much cheaper light bulbs). I pulled ALL the breakers in my apartment to shut down anything in my home, and the noise continues, even though my receivers were DC powered by lead-acid batteries. Yes, I have tried everything you can imagine to reduce the noise on my local mains power. No real help resulted. What a disaster.

  10. The public has voted with their gear. It sounds like it’s time for amateur radio enthusiasts to find workable bands or admit obsolescence. It’s mind-boggling that hams will look at literally the rest of humanity and figure they’re going to force everyone else to clear off for the sake of their own tiny club. Find a workable band.

    1. It’s not just the Hams who are affected. The higher rf noise floor also affects commercial broadcasts, two-way radio systems, and your wifi. The Hams are are complaining because they notice the noise floor every time they operate and they have an effective lobbying outlet in the form of the ARRL.

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