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Wall wart RFI

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N8CMQ, Sep 11, 2017.

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  1. WA7ARK

    WA7ARK Ham Member QRZ Page

    So far, I have found and replaced many extremely HF noisy smps wall-warts at my own place, including the one that powers my CenturyLink DSL modem, one that powers a Win10 Netbook in my ham shack, a vehicular Lead-Acid battery maintainer.

    Habitat for Humanity Thrift shop usually has older-style real-iron transformer-based wall-warts for ~$1 to $3. Most older style wall-warts are unregulated; they just have a full-wave bridge/filter capacitor.

    Most switch-mode wall-warts are internally well-regulated, so replacing them with an un-regulated one might be problematic. I have built linear regulators (using LM317s) to put between unreg wall-warts and the appliance, in some cases. In other cases, I use the shack's 12Vdc power (big battery bank charged with solar or AC as needed) as the input to a linear regulator that makes 5.0Vdc. That way, I can charge cell phones, IPads, and other USB devices even with the AC power out.

    I have a modern RV trailer stored on-site. The #$%^%%$ switching power supply/battery charger in that thing is horrible. It is intended to be plugged-in when parked to maintain the batteries. I solve the problem by using aftermarket real-transformer based battery maintainers, but someday I plan to replace the noisy OEM switcher with a linear supply.

    btw-our newish refrigerator has LED lighting. When the door is opened, I can hear it on a VHF radio located more than 100ft away. Fortunately, the 'frige door stays closed 99% of the time...

    Now if I could get rid of my neighbor's roof-top solar noise generator, I would be happy...
    Last edited: Sep 12, 2017
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

  3. WE6C

    WE6C Ham Member QRZ Page

    I forgot my dishwasher is a Frigidare. It will cause RFI mostly in am broadcast and here and there on other freqs but just use it when not on the radio. Other than that it's a great dishwasher (knock on wood).

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