Wall wart RFI

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

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  1. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    I did not see a forum for RFI alone, so I thought I would share my recent experience here.

    In my post about my Icom 735 restoration project, I mentioned finding a wall wart that was producing RFI so strong, I thought the problem was in the radio.

    Yesterday, 9/10, I had noise that blanked out the ham bands intermittently, it also turned out to be a wall wart.
    This time it was one for my printer. I need my printer, so I unplugged it from the long extention cord it was connected to and plugged it into a power strip close to the wall socket. The noise was substantially reduced!

    I am slowly adding the known noise sources to a switchable power strip so I can turn them off when they act up.
    I hope to be able to prevent noise in the future when the band is weak and the noise is strong.

    I have all of my equipment hooked up to where I can quickly turn power off to it and see if the noise is in the shack now. By doing that,I have even verified the main power supply that runs the Icom also makes a small amount of noise. I also found out my neighbor likes to weld when he gets home from work...

    It isn't bad enough that we have all kinds of natural and man made noise sources outside our environment, but when a wall wart in the shack starts making noise, especially when it is intermittent, just drives you crazy as you are trying to copy a foreign ham just audible over the noise floor as he gives his call and you can't make it out, you want to zap that wart and make it vanish... ;)
    K0OKS likes this.
  2. KI7LGN

    KI7LGN Premium Subscriber QRZ Page

    Truth. I'm finding my worst offenders in the house (besides the #$@% fridge), are all of the USB wall wart chargers for everyone's phones, tablets, ect. I'm almost to the point of making a single big ol' 5v linear PS and using it as a central charging station for everything.

    WE6C likes this.
  3. N3HEE

    N3HEE Ham Member QRZ Page

    I feel your pain! I spent months tracking down and replacing noisy switching wall warts with linear wall warts. Jameco Electronics has linear replacements for most voltages\currents. There is a RFI forum on eHam that is very good.
    WB5THT likes this.
  4. WE6C

    WE6C Ham Member QRZ Page

    You can also buy several adjustable voltage regulators (385 part numbers?????) or something like that. With a few pennies of additional parts you can make just about any wall wart work with anything. There are a few exceptions, but these are handy to have around.
    N8CMQ likes this.
  5. WE6C

    WE6C Ham Member QRZ Page

    A refrigerator causing RFI sounds like a terrible thing. I have a washing machine that when it's running HF is not useable at all however we just wash when convenient so it's doable, plus it's only on for 45 minutes or so. My dishwasher causes a little RFI on AM broadcast and a little here and there but it also has a timer so we set it to run in the middle of the night.

    When the guy came to install my new stove I left several torroids there. My wife asked him to install as many as he could wherever he could. One good thing about him was he knew about them. He wasn't a ham but knew about RFI.

    I'm glad you mentioned this cuzz if I need a new refrigerator I'll make sure if it causes RFI that I can get them to replace it.
  6. KI7LGN

    KI7LGN Premium Subscriber QRZ Page

    Don't buy Frigidaire appliances. One of the draws to the house when we bought it was a complete suite of brand new Frigidaire appliances, within months every single one of them began to suffer problems, ranging from the oven element blowing (and wiping out the PCB board at the same time) to the dishwasher routinely flooding the kitchen, and the microwave eating plates.


  7. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    Gee, I didn't realize I would generate all this static when I brought up this subject...

    I just wanted to hear a little buzz from everyone!

    I like the 7805 and others in the 7800 and 7900 family of regulators, then I use a pass transistor if I need more current.
    BUT... A wall wart is usually a switching supply and the frequency is unstable with most of them. If it is a transformer
    based supply, then the thing is usually quiet and doesn't need fixing.
    With my printer supply, it is a switcher, and it is a higher current unit. I will have to find one that is transformer based,
    and build a filter/regulator board, but I suspect it is a dual voltage unit, but I have not looked at it yet, as I have too many
    other things to do!
  8. W1FBV

    W1FBV Ham Member QRZ Page

    You can find wall warts which are not switchers. I bought several non-switching wall warts from Jameco to replace some offenders.

    73, Jim, W1FBV
  9. K5WY

    K5WY Premium Subscriber QRZ Page

    Marlin P. Jones has a fair selection of transformer wall warts also. MPJA.com
  10. WE6C

    WE6C Ham Member QRZ Page

    I'll grab any transformer type wall wart. They come in handy once in a while.

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