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I have a Raspberry Pi 4 with an external HDD connected (to be precise it is an internal HDD connected with Maiwo K10435) via USB3.0. This setup is placed near my dual-band Wi-Fi router as RPI is connected with an Ethernet cable. Recently I noticed some connection issues for 2.4 GHz clients, 5 GHz worked flawlessly though. After a lot of investigation and experiments, I found that the 2.4 GHz band has a pretty high noise level (something around -82 to -77 dBm). Then I turned off RPI and HDD completely, and almost instantly the noise level dropped to something around -96 to -94 dBm (which is a pretty dramatic difference), and all the connectivity issues were gone. After powering on the RPI setup everything gets back.

I tried switching HDD to USB2.0 port. However, the maximum theoretical speed of USB2.0 is 480 Mbps which should be more than enough for a common HDD, it also affects read/write response times which is not good. So I decided to stay on USB3.0 for now.

What ways of overcoming this issue would you suggest? More detailed technical answers are most welcome, as not so much useful info was found in Google. Mostly the same information everywhere.

  • Could a ferrite filter help significantly? If yes, which specs it should have?
  • Placing RPI setup far from the router (not an option in my case due to topological reasons). How far it should be to neglect the interference?
  • Replacing SATAIII-USB dock. How to be sure it will help? More expensive dock with better cable shielding?
  • Any other options to consider?

upd. Tried putting several different ferrite filters (one by one and all together) to a data cable - no effect. Don't know their specs (even sellers don't), just everything that typically can be found on local electrical markets.

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  • Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer.
    – Community Bot
    Jan 29, 2022 at 9:49
  • How close to the router is the HDD and is there any physical structure, such as a shelf, between the HDD and router? If it's a mechanical HDD, the likely cause of the EMF interference could be the voicecoil, which uses a strong permanent magnet; try moving the HDD to where there is a non-metallic barrier between it and the router. What channel [1 - 11/auto] and channel width [20/40] is the 2.4 Ghz radio configured with? (generally 2.4Ghz radios work best on channels 1, 6, or 11 with a channel width of 40Mhz)
    – JW0914
    Jan 29, 2022 at 14:11
  • No physical obstacles between the router and HDD, they both are placed on the same surface. The distance is around half a meter. The Wi-Fi is currently configured to 13 channel and 40 MHz (it is allowed by the regulatory domain of my country). Other channels are mostly occupied by neighbors' Wi-Fi, so the current setup is optimal (also verified with many channel scanners). But I believe the channel does not really matter as long as you have a powerful source of noise/interference like -80 dBm and above.
    – ihorc
    Jan 29, 2022 at 14:17
  • It’s obvious that channel 13 isn’t optimal if a USB not even connected to the same device is causing interference. Try a different channel before spending money on a different enclosure
    – Ramhound
    Jan 29, 2022 at 14:52
  • Why is that obvious? You may get familiar with the official Inter paper in this regard usb.org/sites/default/files/327216.pdf As you can see from Figure 3-3, the noise from external USB3.0 HDD is spread over a wide range of frequencies, but the highest peak is observed within the 2.40-2.45 GHz range, which covers approx 1-10 Wi-Fi channels. So based on this information, on the contrary, 11+ channels should get less interference. However, the overall noise level is still pretty high compared to no USB3 device connected, which affects SNR and the quality of transmission directly.
    – ihorc
    Jan 29, 2022 at 15:11

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