Interferance that goes beyond blocking the ham stuff

Discussion in 'Ham Radio Discussions' started by KC7YRA, May 22, 2020.

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  1. KK5JY

    KK5JY Ham Member QRZ Page

    If you zoom in to where you can see individual pulses, you can measure the pulse period by highlighting the space between adjacent pulses. You can convert this into a frequency. If it's 60Hz or 120Hz, it suggests that you are looking for something that uses or transmits 60Hz power.
  2. WC5P

    WC5P Platinum Subscriber Platinum Subscriber QRZ Page

    Kind of hard to get a feel for the on-off timing due to all the button pushing, but the timing sort of reminds me of an electric fence charger. One of the locals had something similar a few years back. It was some certain kind of weed getting across an electric fence wire. Solved with a weed whacker. As I recall it affected 80 and 160, but I could be wrong about the bands.
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Fencers usually have a snap sound, no 120/60 Hz because the pulse is very short.

    Perhaps some kind of AC thermostat with bad contacts cycling on and off? Or some other automatically controlled device with bad relay contacts?
  4. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    An electric fish tank thermostat can sound like that. My kids had one, and I fixed it with a 110v a.c. relay, wired so that the thermostat contacts activated the relay which turned on the heater element, instead of turning on the heater directly. That reduced the noise to a faint tick instead of a buzz, and the tick was barely audible in the receiver.
  5. WA1UIL

    WA1UIL Ham Member QRZ Page

    Battery maintainer would be my best guess
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Electric fence with a weed touching it.
  7. K8BZ

    K8BZ Ham Member QRZ Page

    You have taken some pretty reasonable first steps to ID the problem. And I agree with some other posts that it sounds like 60 or 120 Hz noise. It may help if you check to see if the noise is ongoing 24 hours, or if it stops at night or some other regular time f day.

    If you have a portable vhf radio that has AM or SSB mode you can track down the problem even closer than a 2 block area by using even a simple 3 element 'fox hunt' type HF antenna.

    This video is about tracking down noise originating from power line arcing, but it can apply to other RFI sources as well. Good luck.
    K1LKP and N0TZU like this.
  8. KO4LZ

    KO4LZ XML Subscriber QRZ Page

    If you do an audio frequency analysis of the noise in the video, you can see two clear spikes at 60 and 120 Hz, so it would appear to be related to AC power. I'm pretty sure it's not a "normal" AC power line noise issue, since these tend to produce the constant "growl" that you can hear in K8BZ's (very nice) video.

  9. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Use AM BCB or HF portable (loop antenna or walk/drive around method) to find the general area. Then within around a half or quarter mile or so switch to a low air band antenna to get closer, then a high air band antenna to find the individual pole.

    I made a three element “cheap” Yagis for 135 MHz and 335 MHz from stiff copper wire or brass welding rod and PVC pipe (calculators online) with simple hairpin match. A mix 43 ferrite bead at the antenna will help eliminate pickup from the feed line.

    I use them with my HT which can receive the air bands in AM mode.
  10. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page



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