Hash noise from wireless phone charger

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KX4AZ, Feb 11, 2021.

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  1. KX4AZ

    KX4AZ Ham Member QRZ Page

    I have a Seneo brand wireless phone charger stand that emits a broadband hash noise, pulsing at about 3 Hz, that spans the FM broadcast band up to well past the 2m band. It isn't strong enough to completely cover 2m signals, but I can easily hear the noise pulses in the background. It's definitely not due to the switching supply wall wart (I've tried several dfferent ones), but the charging circuit itself.

    Just wondering if this broadband RF noise is intrinsic to the way wireless phone chargers operate....or should I just buy a different brand/model on the hopes I can eliminate it.
  2. WB2LBV

    WB2LBV Ham Member QRZ Page

    Pretty much, I don't think a different one will be better.They radiate crud due to the way they operate.
    I had one in a vehicle that caused hash on 2M and the solution was to unplug it and go back to wired phone charging using it only as a holder.
    KX4AZ likes this.
  3. W7HV

    W7HV Ham Member QRZ Page

    IDK. I don't think they have to emit RFI, but many do. I have not noticed any hash from the Samsung wireless chargers I have. I do get hash from a number of LED lamps, and none from some others. Some of the wife's xmas LED decorations were bad! If it were me, I'd considering ordering one that looks promising from Amazon, trying it, and if it didn't work out, I'd take advantage of their return policy. For us, it's relatively quick and easy to take the item to one of their return drop off locations. Our nearby Kohl's has one.
  4. KX4AZ

    KX4AZ Ham Member QRZ Page

    Thanks for the information; the fact that there are chargers that don't emit EMI is encouraging, so I'll poke around Amazon and order a different brand than what I have and see what happens.
  5. K3EO

    K3EO Ham Member QRZ Page

    Here is a quick experiment that may yield a solution. Try a Faraday shield. Put the phone and the charger inside of a metal container like a cookie tin with a top. You will have to poke a hole through the side of the container for the power cord connection. Steel containers would be the best, but use what you can find around the house or garage.
  6. W7HV

    W7HV Ham Member QRZ Page

    ^^^ what is the goal of this experiment? The OP has already identified the charger as a source. Are you suggesting he builds a Faraday cage to charge his phone it?
  7. KX4AZ

    KX4AZ Ham Member QRZ Page

    One last post to close out my story on this...I ordered a different wireless charger model from Amazon ("Youtech" brand; FCC ID: 2AOSUX2S; $11.89). The fact that it even purported to have an FCC ID was a positive sign....but of course it could have just been a copycat. So the proof is in the pudding....and a quick test revealed there was no significant hash noise in the VHF spectrum, as there had been with the Seneo brand charger. Looking at the 2m spectrum from the outdoor discone antenna (about 100 feet from the charger stand), I can no longer see a rise in the noise floor when the phone is charging. Before I start poking around the HF spectrum and discover it has been ruined, I will declare victory and enjoy my triumph over VHF noise.

    The Seneo charger is now headed to the dumpster, after I fill its micro-USB power port with super glue or epoxy. Alternatively I'm happy to offer it free (you pay shipping cost + $20 handling fee), but only to an out of state recipient ;>.
  8. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    This is one reason why I never buy cheap-axx off-brand chargers.

    Another is that they probably don’t have proper insulation between the AC and DC sides since they typically don’t have UL or other safety agency listing. Finally, phones and phone batteries are expensive and a cheap charger may not be well regulated.

    Always get the phone brand or at least a well known quality aftermarket brand such as Belkin.
  9. W7HV

    W7HV Ham Member QRZ Page

    ...should you run into issues on HF, one thing to try before returning it to Amazon would be put a couple of turns of the cord near the charger through a clip-on ferrite of appropriate HF mix.
  10. WB2LBV

    WB2LBV Ham Member QRZ Page

    The one I had issues with was a Scosche which is a decent brand so that's not a guarantee, although I agree that the cheap ones are best avoided.

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