Hum on transmit which goes away when I touch the radio

Discussion in 'General Technical Questions and Answers' started by KE0EYJ, Jun 15, 2018.

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  1. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    So I bought an ebay patch cable for my Icom 7300 last year, because I had no idea at the time where to get the parts here in Korea (I'm in Seoul) to build my own.

    The thing works, but there is a low/dull hum when I transmit. If I touch the radio, however, it goes away. I wrote the seller/maker about it (he's a ham who makes patch cables and sells them), and this is what he wrote back:

    Now here's the problem....

    All of the wires are connected as he said they should be.

    BUT... I don't have a multimeter. If I had had a multimeter, and known how to use one, I probably would have never needed to purchase a patch cable, right?

    Side note: Multimeters are crazy money here in Korea... I can't just waltz down to a Lowe's or buy one online for cheap. I'm spending $50 for a low-end Chinese one, in Korea. There seem to be some kind of market protections on them, here.

    So, I asked for a multimeter for my birthday, and my father sent me one he'd purchased on Amazon. Got the multimeter after waiting for shipping...opened it up, and didn't work at all. Numbers going crazy all over the place, no matter what setting. So I'm stuck with a multimeter we paid to ship here (along with my other gifts), and so pissed I don't want to spend $50 in order to check a $10 patch cable. I'm leaving Korea next year, and won't be bringing much of anything, so there is no point in purchasing one now.

    Anyway... so I still have this hum. I checked all of the connections, and they are correct, per what he said. The radio is an Icom 7300. I have another patch cable (for a dynamic) which works just fine. I had purchased that elsewhere.

    Hums with two different brands of headsets. Don't have others to try. Any suggestions? I'm sure annoyed by this. Thanks.
     
  2. VK3YE

    VK3YE Ham Member QRZ Page

    Check your rig's power supply.
     
  3. K1FBI

    K1FBI Premium Subscriber QRZ Page

    I have a feeling that multimeter works fine.
     
    KD4MOJ and KD9KSO like this.
  4. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    Seems to work fine. No issues with the dynamics? It's a Diamond GSV3000 linear.

    I wonder if there are issues because I'm 220v, and there is no way to ground the plugs, here?
     
  5. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    I couldn't get it to work. Just random jibberish numbers on every setting, that moved constantly and showed no specific reading when I tried to test anything.
     
  6. W5DXP

    W5DXP Ham Member QRZ Page

    Did you try fresh batteries for the multimeter?
     
  7. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    Yeah, no good. :(

    I have been asking friends nearby in JA (I'm HL1ZIX here) and they don't hear the humming sound. It seems to be mostly below 150hz. Drives me batty, if I listen for it. Will keep the monitor off, I guess.
     
  8. KI4AX

    KI4AX Ham Member QRZ Page

    Is your rig grounded? Are there any Florescent Lights near your operating position?
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    What are you listening to it with ?

    Is your radio grounded ?

    If you short the leads on your new meter together does it still go crazy ?
     
  10. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    Not grounded. I'm on the 3rd floor of a building that is 220v with no center ground available for even the plug. I'm also at the corner of a building within 8 meters of a high power line junction, so that could be it, also.

    I know the building has a ground rod at its center, but not sure how I could tap into it, from here, without running a line down 3 floors outside of the building. Doubtful that would do much.
     

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