Identification/Management of QRM triggering on FTM-3200D

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by AB1YW, Apr 7, 2020.

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  1. AB1YW

    AB1YW Ham Member QRZ Page

    My FTM-3200D has possibly the most obnoxious behavior around some of the local RF interference. The interference is just strong enough to trigger the receiver and start reading on the S meter, but is transient enough that it cuts out promptly. This results in the mode light blinking green and the audio amplifier powering up with an audible pop-click. Needless to say, this happening intermittently and frequently essentially makes the radio useless as an effective tool.

    Current antenna setup is a short mag-mount on my unplugged window AC unit sitting inside and under my apartment window.

    Depths of diagnostics, because I certainly tried something about this:
    • Set squelch on radio to 5+: audio amp still powers up and lights turn on; interference sometimes indicates higher than 5, anyways
    • Alternate AC/DC power supply: no change
    • Dummy load on radio: nice and quiet
    • Alternate antenna: HT antenna on a BNC cable slightly lowers ocurrences of receiver activation
    • HT on current antenna: my VX-2 does not have any intermittent signals displayed on the S meter
    • Poking around with a USB SDR: eliminated a poorly shielded Qi charging stand, but that wasn't the cause; still can see some 100 kHz spaced interference poking out of the noise floor, barely
    Any suggestions on tracking down the interference or otherwise making my radio more usable? I'll have improved SDR receiver capabilities once I get some repairs done.
    KK4CUL likes this.
  2. AB1YW

    AB1YW Ham Member QRZ Page

    Full quieting from the local NWS radio keeps the pops down with continuous audio. Still looking to figure making this rig usable.
  3. WA4SIX

    WA4SIX Ham Member QRZ Page

    What is the time pattern?
    When AC turns on? Is AC digitally controlled?(Could be temp sensing circuit coming on in intervals)
    Do you have a battery maintainer on a lawn tractor?

  4. AB1YW

    AB1YW Ham Member QRZ Page

    Ed, here's a quick clip of the behavior with just the radio turned on and hooked up to the antenna: (70 MB file, not sure if Google does some fancy down sampling on the web preview of the shared version)

    Interval is inconsistent noise, 1-10 second pauses between the pops, as illustrated. Too fast and repetitive to be a plug load of some sort, but I'm also an apartment dweller, so any nearby neighbors or power lines could be contributing. Same thing at any hour of the day. The A/C has been off for months and there aren't any vehicle battery chargers around that I know of.
  5. WA4SIX

    WA4SIX Ham Member QRZ Page

    Many computerized battery charger/maintainers come on long enough to check state of charge. It sure looks like that. I got no audio from the file.

  6. AB1YW

    AB1YW Ham Member QRZ Page

    The audio in the clip is (consistently) very quiet. Turning up my volume, I was able to hear the pops, but you can assume it happens with every green light blink.

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