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Thread: Tracking down an HF noise source

  1. 08-26-2014, 01:19 PM #1
    NQ6U
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    Tracking down an HF noise source

    I tried to have a 10m QSO with Jim, KJ3N, this morning and was foiled by a nasty S-3 buzz across the entire band that pretty much wipes out all but the strongest signals. Further investigation showed that it exists over the entire HF spectrum, from 80m on up. I'm not exactly sure how to track something like this down. The 746PRO is a little awkward for portable use.

    Any suggestions?

    On Edit: It's not emanating from anything in my shack. I turned off everything but the rig. To eliminate a possible problem with the Icom power supply, I also listened with the 736, which has it's own PS built in and heard the noise with it as well.

    On Further Edit: I got out my old Sangean ATS-803A portable SWL radio and could clearly hear the noise outside the house. Throwing the main breaker at the service entry point made no difference, so it's not coming from here.
    Last edited by NQ6U; 08-26-2014 at 01:53 PM.
    All the world’s a stage, but obviously the play is unrehearsed and everybody is ad-libbing his lines. Maybe that’s why it’s hard to tell if we’re living in a tragedy or a farce.
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  2. 08-26-2014, 01:50 PM #2
    K0RGR
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    The standard method is to have someone turn off the circuit breakers in your house one at a time until the noise goes away, then track the problem down on the circuit that makes it come and go. A portable AM radio should work for hearing the noise, a portable aircraft band receiver would be better.
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  3. 08-26-2014, 02:03 PM #3
    NQ6U
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    Quote Originally Posted by K0RGR View Post
    The standard method is to have someone turn off the circuit breakers in your house one at a time until the noise goes away, then track the problem down on the circuit that makes it come and go. A portable AM radio should work for hearing the noise, a portable aircraft band receiver would be better.
    Done. The noise is not coming from within the house. I walked the neighborhood with a portable HF receiver and the noise seems strongest in the general vicinity of my QTH, but I need a more directional antenna to narrow it down. Unfortunately, it seems as if the noise source is pretty quiet in the AMBCB.
    Last edited by NQ6U; 08-26-2014 at 02:08 PM.
    All the world’s a stage, but obviously the play is unrehearsed and everybody is ad-libbing his lines. Maybe that’s why it’s hard to tell if we’re living in a tragedy or a farce.
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  4. 08-26-2014, 02:09 PM #4
    K7SGJ
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    Carl, you should be able to use the portable radio to help out. See if it is present on the AMBCB. This is the best thing to use, since the antenna inside is a ferrite loop type, and is very directional. The HF antenna is probably a rod and not very directional.
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  5. 08-26-2014, 02:10 PM #5
    NQ6U
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    Quote Originally Posted by K7SGJ View Post
    Carl, you should be able to use the portable radio to help out. See if it is present on the AMBCB. This is the best thing to use, since the antenna inside is a ferrite loop type, and is very directional. The HF antenna is probably a rod and not very directional.
    We posted within seconds of each other, but see above. There seems to be a peak in signal strength at about 19.5MHz. My radio does have an external antenna jack, so I should be able to rig up some sort of loop antenna.
    Last edited by NQ6U; 08-26-2014 at 02:12 PM.
    All the world’s a stage, but obviously the play is unrehearsed and everybody is ad-libbing his lines. Maybe that’s why it’s hard to tell if we’re living in a tragedy or a farce.
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  6. 08-26-2014, 02:13 PM #6
    K7SGJ
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    Quote Originally Posted by KJ6BSO View Post
    We posted within seconds of each other, but see above. There seems to be a peak in signal strength at about 19.5MHz. My radio does have an external antenna jack, so I should be able to rig up some sort of loop antenna.
    Good show. Do you get it off station on the AMBCB?
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  7. 08-26-2014, 02:19 PM #7
    n2ize
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    If the portable has a gain control bring the gain way down till the noise is way down and move around The noise should start coming up as you get close to the source.
    I keep my 2 feet on the ground, and my head in the twilight zone.
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  8. 08-26-2014, 02:19 PM #8
    NQ6U
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    Quote Originally Posted by K7SGJ View Post
    Good show. Do you get it off station on the AMBCB?
    No, not hearing it there at all. I'm guessing it's a commercial device that was tested for RFI on the AMBCB but not elsewhere.
    All the world’s a stage, but obviously the play is unrehearsed and everybody is ad-libbing his lines. Maybe that’s why it’s hard to tell if we’re living in a tragedy or a farce.
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  9. 08-26-2014, 02:20 PM #9
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    Quote Originally Posted by n2ize View Post
    If the portable has a gain control bring the gain way down till the noise is way down and move around The noise should start coming up as you get close to the source.
    Yeah, it does, and I'm working on that.
    All the world’s a stage, but obviously the play is unrehearsed and everybody is ad-libbing his lines. Maybe that’s why it’s hard to tell if we’re living in a tragedy or a farce.
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  10. 08-27-2014, 12:36 PM #10
    XE1/N5AL
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    One by one, cut the power lines to each of your neighbor's homes until the noise goes away. You can salvage all that wire you've collected for building future amateur radio antenna projects.

    Is the noise a constant-pitched buzz, or does it change over time? Is the noise present 24/7, or just during certain hours?
    Last edited by XE1/N5AL; 08-27-2014 at 12:37 PM.
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