frame from waterfall display videoI'm getting a lot of noise now that I have a dipole higher up. The pattern on the waterfall makes it seem man made.

Could it be power line? Or is it some kind of motor?

Here's a short video of the display and waterfall: https://streamable.com/podpf3

EDIT: as requested here is the same frequency in AM mode


Also here are some other higher frequencies


  • $\begingroup$ Is the noise across the whole band, or only when you tune to one of those vertical lines? My guess it's the former. $\endgroup$
    – Mike Waters
    Jul 10 '20 at 20:06

It's possible that someone on this site may be able to definitively identify your RFI by watching the short video of your waterfall display, but I doubt it. Perhaps the best way to identify the type of RFI that you're dealing with is to discover where the RFI is coming from.

A simple test could be to switch circuit breakers in your house or apartment off. If the noise goes away when a breaker is off, then you know the noise generator is powered by that circuit. It's possible the noise could have something to do with your radio because intermodular distortion, a bad component, etc. In that case, if you can get your hands on another receiver with a waterfall display, then you might learn something by temporarily using the other radio in place of yours.

If you are reasonably certain that the problem isn't in your radio, your house or your apartment, then there's a good chance that the noise is coming from your neighborhood. An easy thing to do is ask another nearby ham if he or she can hear the noise. A portable receiver and antenna can be a big help here. Maybe someone in your club has an HF rig installed in his or her car, and wouldn't mind driving around with you to see where the noise is stronger and weaker. If the noise is clearly coming from a neighbor's house, maybe the neighbor wouldn't mind flipping circuit breakers to help you find the source of the RFI.

The ARRL has a very helpful web page about RFI here containing lots of links to other articles. Also the ARRL has written a book about the subject, the ARRL RFI Book, which is surely packed with excellent advice.

  • $\begingroup$ that would be a tough sell to the iCom warranty claims department that the radio itself is causing the interference $\endgroup$
    – Paul
    Jul 10 '20 at 1:11
  • 2
    $\begingroup$ @Paul easy to figure out if the interference is an intermodulation product: turn on the attenuator or add a discrete one on the feedline. The signal power will go down of course, but does the interference go down more than the value of the attenuator? If so, it's likely an intermodulation product. Not necessary a fault in the radio, it could just be really strong interference. $\endgroup$ Jul 10 '20 at 4:53
  • $\begingroup$ Isn't 3.785MHz the NTSC color burst frequency? Could that be related? $\endgroup$
    – Duston
    Jul 10 '20 at 13:29

That sounds like an arc in an insulator, lightning arrestor, or loose hardware on a 7 kV power line.

The repeating patterns might indicate otherwise, but I have seen those on the wideband SDR that the power company's chief engineer brought over a couple of years ago. They were the results of certain lengths of the 7850v line resonating with an odd harmonic of the 60 Hz power line frequency.

Seeing that that noise is present on another band without those repeating vertical bars on your 7300's FFT display, it is very likely power line noise.

  • $\begingroup$ huh! Interesting! How can you tell the line's voltage? $\endgroup$ Jul 9 '20 at 16:56
  • 1
    $\begingroup$ Thanks Mike- I edited the question and added more recordings $\endgroup$
    – Paul
    Jul 9 '20 at 18:26

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