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I live in a condominium apartment building. I have a Bose Wave Radio with a dipole antenna connected. I frequently listen to FM radio stations. One of the stations I listen to has pretty good power and I always get a clear signal; the other is a little lower power, so sometimes it gets a little staticky depending on the exact position of the antenna and where I'm in the room (it's also finicky on my shower radio).

I have a neighbor in the apartment immediately above mine who frequently uses her shredder. Whenever it's running, I hear lots of static on the radio. This affects both stations.

Is the shredder emitting radio interference, or is this likely related to the electrical circuit in the building?

Is there something I can do to mitigate this? The noise from the shredder is annoying enough, but the radio static makes it worse.

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    \$\begingroup\$ Try borrowing a battery powered receiver to see if this works under the same scenario. If it doesn't then it's air-borne interference. Does your shower radio pick up interference - is it battery operated? \$\endgroup\$
    – Andy aka
    Commented Jun 17, 2022 at 15:43
  • \$\begingroup\$ Many dipole connections to radio is via a short (like 1m) transmission line, requiring the antenna to be inside a building where you listen. Can you extend the transmission line so that dipole can be placed outside, preferably well-above ground? \$\endgroup\$
    – glen_geek
    Commented Jun 17, 2022 at 15:47
  • \$\begingroup\$ @glen_geek The radio sits near to a sliding glass door that goes to a small patio, but I don't see any easy way to get the antenna through it (and I wouldn't want it open during the winter). \$\endgroup\$
    – Barmar
    Commented Jun 17, 2022 at 16:00

2 Answers 2

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Take a look on the bottom or back of your radio. You should see something about FCC rules Part 15:

FCC part 15 rules

(Source)

In particular:

This device must accept any interference received, including interference that may caused undesired operation.

Unfortunately, your neighbor's shredder is most likely an unshielded motor with a gearbox and a perfect example of a wide-band RF noise generator. It basically spews electromagnetic interference (EMI) when it's on. The reason that is allowed is because it is fairly limited in power and range; it's not a transmitter. You just have the unlucky circumstance of having your receiver near it.

There are a few things you might do:

  • Chat with your neighbor about moving it to a different location in her apartment. It may be that simply moving it helps.
  • Consider moving your receiver; for the same reasons as above, putting some distance between it and the shredder may help enough.
  • Extend the antenna location with a shielded coaxial cable. You may be able to move the antenna to a location or position that is away from the shredder or oriented to reject noise from it, while leaving the radio in the desired location.
  • In theory if your neighbor was very concerned, she could wrap the shredder (at least partly) in shielding and ground it to attenuate a lot of the noise. However, it would be ugly and inconvenient, so don't hold out for this solution.

I almost forgot to address the shared electrical power issue. The shredder can also inject noise back to the circuit from which it's powered. In that case, if you share an electrical circuit (or even if it's not shared, but your two circuits are short distances away from a common breaker panel) the noise could be originating from power instead of exclusively being picked up in air. Some things to try:

  • Move the radio to a different outlet, hopefully on a different circuit. Depending on the size of your apartments, this may or may not make a difference.

  • Add a filter (ferrite bead) to the power cord, to help remove higher-frequency noise.

    Ferrite bead choke

    (Source)

  • Power the radio from a battery or uninterruptible power supply that is disconnected from the apartment circuit. (As Andy suggested in comments.)

If you are able to identify that the bulk of the noise/interference is coming from a shared electrical connection, you may be able to take more steps to isolating it. But those are my most immediate suggestions.

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    \$\begingroup\$ A ferrite bead just clamped around the power line would only function to filter out common-mode noise, I believe. Any differential-mode noise would be unaffected unless you separate the conductors and run only one through the bead. The noise to be filtered may be differential or common mode, or both, so I'd still think it worth a try since ferrite beads are cheap. \$\endgroup\$
    – Hearth
    Commented Jun 17, 2022 at 17:11
  • \$\begingroup\$ @Hearth That's a good point, thank you. \$\endgroup\$
    – JYelton
    Commented Jun 17, 2022 at 21:42
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The dipole antenna connected to the Bose Wave Radio might have a pretty good null off the ends. Since your neighbor is in the apartment above you, it's worth a try using that null to reduce the interference. Orient the dipole vertically, not horizontally. You can also tilt it somewhat. Have the neighbor run the shredder while you try various tilts and orientations of the dipole.

Historically, FM radio stations transmitted horizontally polarized signals, but with the appearance of car radios using vertical whips, they all converted to circular polarization. Because of this, orienting your dipole vertically should not reduce the signal significantly.

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  • \$\begingroup\$ The antenna is actually just laying on the floor, not oriented in any particular way. Occasionally when the station isn't coming in well I'll move it around randomly until things get better (like the old days when people would fidget with a TV antenna). \$\endgroup\$
    – Barmar
    Commented Jun 17, 2022 at 19:03
  • \$\begingroup\$ @Barmar: As a temporary experiment, you could try hanging it from the ceiling if it's short enough to run straight that way. Right under the shredder might be ideal, as this answer points out: one end pointing straight at the shredder, wherever it is, should be a direction that it's not sensitive to. OTOH, farther from the shredder but still pointing at it might be much better. Long term, running up a wall, or angled toward the shredder along a bookcase, might work. (Cooperation from your neighbour in terms of moving her shredder to somewhere that makes this possible might be good.) \$\endgroup\$ Commented Jun 18, 2022 at 21:16

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