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Sunday, March 7, 2021

EXORCISM! 40 Meter RFI Problem Resolved


David W. suggested I use my RTL-SDR dongle to look for the source of the 40 meter RFI that I have been mentioning.  (It appears as an ugly stipe in the waterfall of my Hodgepodge transceiver.) So I fired up the RTL-SDR -- there were the tell-tale spikes, spaced neatly every 50 kHz.  The ARRL Handbook says this is typical of a switched power supply.  Before I started patrolling the neighborhood with a tin-foil hat and a portable receiver, I decided to check my own house for any recently installed electronic devices.  It didn't take long -- when I unplugged the new (mid-pandemic) treadmill the spikes disappeared.  This treadmill was located about ten feet above my rigs, and between the rigs and the antenna.  Duh.  I should have thought of this earlier. Mystery solved.  Thanks David. 



  1. I like the Leviton 1470 switches - allows me to turn off stuff that doesn't have an on/off switch !

  2. Wireless power switche are even better! For lazy people like me. :) Remote or wifi. (Phone, Google Assistant, or Alexa driven)

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  4. Just confirms the harm that exercise can cause.


  5. Even with the device powered off through the switch you were seeing the interference?

    I have witnessed some badly made electronics that 'leak' from the ground and give spikes like this.

    1. No, the RFI disappeared when I turned the switch off.

  6. I'm happy to hear that my suggestion pointed you to the path of success and not perdition.


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