Hearing my voice coming from the AMP when transmitting.

Discussion in 'Amateur Radio Amplifiers' started by W9ZMB, Oct 24, 2020.

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  1. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    I'm setting up a mobile HF station in my Toyota Tundra consisting of an iCom 7100, Ameritron ALS-500M (controlled with a ARI-500), and a Scorpion SA-680 Antenna. The radio and amp will be mounted inside a bed mounted tool box. All coax connections currently have at least one snap on ferrite bead on them, with the amplifier output having a larger one and three wraps of coax going through it. There is also a DX Engineering Current Choke and the near the antenna connection that exits the box.

    At present the radio and amp are mounted in the box, and the box is on a bench in the garage, and I'm feeding the box with two Astron 70A power supplies run in parallel, and transmitting into a 1KW dummy load. I'm currently testing the system to make sure that the wiring is right and to make sure I have eliminated all (or as much as I can) the RFI.

    The issue I'm having is that when I transmit with the amp off everything works correctly, and the meter is showing the amount of power output that an unmodified 7100 should see at the dummy load. However, when I turn on the amp and transit I can hear my voice coming out of the amplifier.

    so my question is: Should I be hearing my voice coming from the amplifier? and if not, what should I do to fix it?
  2. WA4SIX

    WA4SIX Ham Member QRZ Page

    If the input & output SWRs are good, you should be fine.
    Probably the ferrite transformers rattling a bit. Hot melt glue would solve it.

  3. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    Kewl. I guess I'm going to have to buy ANOTHER SWR meter. lol. The one I have is on cable connected to the dummy load. Always good to have more than one of something. lol.

  4. K7JEM

    K7JEM Ham Member QRZ Page

    As long as it is your own voice, and it's not telling you to do bad things, you're most likely OK.
    AC0OB, N4ABA, K9ASE and 5 others like this.
  5. K6BSU

    K6BSU Ham Member QRZ Page

    I operated a BC-610 for a couple years in Alaska. The modulation transformer "sang" back to me. Far from hi-fi, and I just got used to it.
  6. WA4SIX

    WA4SIX Ham Member QRZ Page

    Doesn't your radio have a built in SWR meter? That would show input SWR.

  7. WJ4U

    WJ4U Ham Member QRZ Page

    Joel, if you hear heavy breathing, you may need a new mask filter. ;)
    AC0OB, K9ASE and W9ZMB like this.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I agree, likely ferrites acting like piezoelectric resonators.

    "One" snap-on ferrite on power leads and such does nothing at HF...I've always found it takes 5-6 of those to do anything at HF. One may work at VHF.

    Note the "W2DU current baluns" use 40 ferrite cores slipped over the coax and heatshrinked to hold them together.:)
  9. W9ZMB

    W9ZMB XML Subscriber QRZ Page

    Yes it does, and it says I have a 1:1 SWR when I'm transmitting into the Dummy Load. however I was always told that the internal SWR meters are inaccurate, so I always go by an external one.

    All radio power cable bundle is wound through a 3/4" id snap on ferrite core with three turns (that all that I could get through it). The Amp power cable bundle are the same thing through their own core.

    The Coax jumpers from the radio to the Turbo Tuner and the Turbo Tuner to the amp both have 2 snap on ferrite corps on them. The jumper from the amp to the current choke is run through a 3/4" id ferrite core with three wraps (all I could get through it) and the jumper from the choke to the connection out of the box has 2 snap on ferrite cores on it.

    Do you think I should put more on them?, if so what would you suggest?
  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    Internal SWR meters should be just fine. Power up the amp & check input & output SWR. Mu guess is that they are fine.


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