USB Charger Causing Radio Interference -RFI

Discussion in 'Ham Radio, SDR & Police Scanner Technology' started by Titanium, May 18, 2017.

  1. RF noise (both generating it and suffering from it) typically isn't among them.

    There are good and bad examples of every technology.
  2. My USB wall outlets interfere with my hd table radio., just the ones next to the radio.
  3. It takes some pretty serious noise (or a not fantastic radio) to interfere with FM. Are you hearing the interference on AM, FM or HD?
  4. I haven't checked the AM or FM, but it definitely interferes with the HD signals.
  5. If it is interfering with the Hybrid Digital signal, that's probably a defect/fault of the radio itself. Digital decoders typically can't decode a signal that has been interfered with so I'm suspicious that the interference is coming in after the decode section.

    Of course if a quality AC adapter addresses the problem with the radio, everybody's happy.
  6. Like I mentioned, I'm using a wall USB outlet. The radio is a Sangean, supposedly a good one.
  7. Doesn't matter if the radio is cheap, expensive or well constructed. If a device is generating a signal, a tuner will receive it. A quality radio may have better rejection and/or shielding, but every receiver needs an antenna.

    Viewing the radiated broadband noise from various chargers with a scope, the RF garbage is generated across broad swaths of frequencies. Tuning HF/VHF/UHF frequencies with a Yaesu FT-991, LMR400 feedline and external antennas 100' away, several wall and 12VDC USB chargers are received in analog and digital modes with sufficient strength to prevent reception of stations that are easily copied when the charger is unplugged.

    It's all about Signal to Noise Ratios... if the charger presents a signal that competes with off air signals, radio reception will be affected.
    KE4EST likes this.
  8. I thought it was all about the Bass. :D
  9. But in this case, the signal being stomped on is digital and that's not something that gets interfered on as readily and if it does, it is most likely going to be considerably trashed, not just interfered with.
  10. I have experienced digital radio interference first hand... Interference affects both digital and analog signals. Yes, the digital cliff is often a hard cut, but I often hear digital radio signals get choppy, chips, tone blasts, etc... all effects of poor signal to noise ratio causing decoding issues.

    Yes, raoul5788, the wall wart is likely causing interference with your digital radio. Chargers, controllers, power supplies, ballasts, (insert any device capable of radiating wanted or unwanted signals), etc. cause reception interference in both the analog and the digital worlds.
    raoul5788 likes this.
  11. Sangean makes excellent equipment and as the link I provided earlier witnesses, their new wall warts (such as the one used on the HDR-18) are remarkable.

    When you say "wall USB outlet" is this a wall wart with an A jack or an electrical duplex outlet that has USB charging ports built in similar to the one pictured below?

  12. #32 raoul5788, Aug 4, 2017
    Last edited: Aug 4, 2017
    This is the one. e32513ae-601e-461c-9272-e3a4a0bdd358_1000.jpg
    I've had the radio nearly ten years. It's the HDR-1.
    Maybe it's time to upgrade.
  13. Shouldn't need to buy a new radio to address interference, but that may be a simple option if the source can't be addressed. The HDR-1 has limited options as it has an internal power supply and limited antenna relocation options.

    Is the HDR-1 plugged into this outlet or same breaker? Does the interference go away if the HDR-1 is plugged into a different outlet on different breaker? If not, will the interference go away if the USB outlet breaker is turned off? Does the proximity of the HDR-1 to the USB outlet affect the amount of interference? These tests would point to the way the USB outlet interfering signal is being distributed and possibly provide ideas on how to attenuate or eliminate. Is it interfering via the electrical connection or over the air?

    If the USB outlet is back feeding the breaker box, then your entire electrical system becomes an antenna to radiate the I interfering signal. If so, it might be possible to isolate the USB outlet from the breaker or even use ferrites on the AC distribution runs to the outlet and minimize the interference. If I discovered the hardwired USB outlet was backfeeding the interference into the electrical system or radiating from the device, I would contact the company for a solution. It's not like it's a portable charger that can be moved/removed as needed.
    KE4EST and harshness like this.
  14. I'm using the same outlet for the radio and for charging. I haven't tried a different one for the radio or anything else you suggested except unplugging the data cable does bring back the radio reception.
    Titanium likes this.
  15. Unplugging the USB cable turns off the 5V power supply in the outlet so that definitely pinpoints the outlet as the source of the interference.
  16. Yes, but what happens if I use a different outlet, particularly one on the other leg of the service?
  17. raoul5788

    Test and reply following my suggestions. We need to determine the signal path of the USB outlet interference into your radio. AC power distribution or via air waves?
    raoul5788 likes this.
  18. I will, thanks for the guidance.