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Is there a way of identifying between common continuous household RFI/EMI sources (USB1/2/3, iPhone/iPad wall warts, cable/DSL modem, ethernet 10/100/1G, light bulbs, etc.), (e.g. which one, if any?) just by looking at a (VHF) SDR or other spectrum analyzer waterfall display?

Does the FCC or UL (et.al.) or other public resource keep a database of fingerprints of common RF noise sources?

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This is an interesting topic, and in fact was the main subject of the DARPA SDR Hackfest in Brussels January/February this year. https://fosdem.org/2017/schedule/event/darpa_hackfest/ (huh, I'm even on that video – at least the back of my head is)

So, no, to my knowledge, there's not such a database by now, and you'd have to build up experience yourself, though chances are that a few sources are easy to spot – supplies will have spectra of square waves, USB devices have an 11MHz oscillator, 1GigE runs at 125 Mbd (but I don't believe it's going to be very prominent – these cables are usually well-designed :) ), and you can test a light bulb SMPS hypothesis by turning of lights.

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The question is indeterminate since the I in EMI is the product of some unintended radiation and same spectral susceptibility in some target device.

So the most generalized case is unshielded wires of high current pulses [A/us] and high voltage [V/us] slew rate and high EM fields [V/m], [A/m]

The actual spectrum of transients that are slew rate limited may not be excessive but no less problematic with IO cables acting as antenna.

The spectrum of arcs are the broadest and repeating arcs in a small gap span the frequency up to the half wavelength of the gap and then beyond with harmonics.

Cars now use carbon sparkplug cables which current limit the ignition arcs to the plugs and thus limit the spectrum that interfere with radios, in particular AM, which is a great improvement over copper wire sparkplugs of long ago.

1Hz Xenon safety flashes in a factory where high voltage tests are conducted are well known to interfere with many cell phones due to the high EMI pinging the AGC's in the receivers with broad spectral noise spanning many GHz from the ionization impulse. (Even more-so than arc-welders) This may be limited to one supplier's poor design conformance to unintended radiation.

I have conducted many product tests for radiated, conducted and susceptibility tests before release to production. ESD, impulse conducted, radiated and pulsed RF sweeps as well as radio adjacent channel and co-channel susceptibility tests in addition to routine Hipot dielectric withstanding tests. This is an essential Design phase.

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  • \$\begingroup\$ The susceptibility will be high, since most VHF SDRs and spectrum analyzers can be used with wide band antenna's. But where might all that very common periodic in time and frequency and often very similar looking noise coming from in online waterfall plots from all over the world? Some common standard cheap cable that people all over the world uses? \$\endgroup\$
    – hotpaw2
    Mar 14, 2017 at 2:29
  • \$\begingroup\$ Analysis only comes from experience unless your SA has bands labelled. \$\endgroup\$ Mar 14, 2017 at 2:36
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Is there a way of identifying between common continuous household RFI/EMI sources just by looking at a (VHF) SDR or other spectrum analyzer waterfall display?

Yes, with the appropriate SDR, antenna and amplifier, you could identify potential noise sources. I bought a spectrum analyzer and a probe set (I'm not affiliated with beehive electronics), you can even identify noise sources on a PCB like clocks. Some of the signals are at the lower limit of the spectrum analyzer so I would get some good amplifiers. An SDR would also need to be calibrated if you wanted to use the numbers for anything, but if your looking for sources it should work great if the signal is within the dynamic range of the setup. The bandwidth of the SDR system would also need to be in the same range as the bandwidth of interest.

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Does the FCC or UL (et.al.) or other public resource keep a database of fingerprints of common RF noise sources?

No, that is probably more information than the government wants to keep track of. The FCC imposes an upper bound of RF noise on products so they don't have to keep track of the noise level.

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