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AM antenna QRM issue

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    AM antenna QRM issue

    AM antenna QRM question:

    I have a large outdoor Wellbrook flag loop. It's performed well over the years. Tonight I got up to my site, hooked up, and am getting spurs all over the band, from LW through to the top of AM. Some of the spur signals seem to be shortwave and I'm also getting teletype and other noise. It's my west directional antenna. A second similar antenna (north-south) is fine. I swapped out the Wellbrook antenna interface using a spare one I have, same problem. I also tried another power supply. Not that.

    One DXer suggested I look for connection problem which can cause all kinds of IM mixing. I did that at daylight this morning, and the actual antenna hookups seem fine. I even took it off and pout it back. My two antennas are entirely separate. The feed into the problem antenna is clean.

    Aside from the spurs, which are all over the place, there’s QRM sounding like ... an audio clip is attached here, which includes loud teletype (thankfully not on all channels) and the underlying click-type noise.

    Any thoughts?


    Attached Files

    Originally posted by Saul View Post
    I ... am getting spurs all over the band, from LW through to the top of AM.
    That description sounds like noise from a poor switching power supply. They could be in the form of a wall wart to streetlights to anything electronic. Stop lights are notorious these days--a switching power supply in a control box a few feet above ground feeding lights above an intersection via long wires serving as a transmit antenna.


      Thanks! None of those, though I do have some usual local noise. I've done an array of swapping out of various components of my two antennas and am pretty certain the culprit is the FLG antenna box. these are sealed and not really repairable. I have another that works, but now can operate only one antenna at a time, though I could get a switch and /or another box.


        You have an easy way to confirm if your FLG antenna box is at fault or not.

        I was taking about the switching supplies in your TV, computer, appliance, screw-in LED fixture bulbs, city streetlights, etc. in or around you or your neighbor's house. Lower priced ones sometimes leave out the needed filters to save a few cents.


          Thanks. I was getting imaging and spurs - even some obvious shortwave and utility and teletype signals - which have never appeared even when I have dealt with the occasional electrical QRN issue at my rural site. Caused by the cheap crap you so accurately describe. We live in an age of cheap, sadly. Perhaps the worst culprit here is the furnace, and at times I've singled out particular light fixtures and appliances. But my coax goes far enough out the door that these sources aren't much trouble. My antennas are also decidedly as far as they can be to hydro poles. This was completely different. Luckily I had two FLG boxes so was able to swap them and determine one was at fault.