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TS-850/DSP-100 TX issues

Discussion in 'General Technical Questions and Answers' started by W2KS, May 17, 2018.

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  1. W2KS

    W2KS Ham Member QRZ Page

    I have a TS-850 that was modified extensively for ESSB and a DSP-100. I am using Behringer audio equipment for EQ enhancement. Here is the problem: When I transmit on 40m, I keep getting a heavy, thumping oscillating beat that continues even after I release my PTT hand switch. When I drop the gain on the Behringer preamp, it stops. Then I have to readjust the preamp gain control to get the rig to work without the oscillating. Of course, power drops considerably. I am running power from an AL-80B and use an "audio pecker" to tune the amp and antenna. This doesn’t happen on any other band. Just 40m. However, when I transmit into a dummy load, everything works perfectly on 40m. This confuses me. Is there possibly something wrong with my TS-850, DSP-100, or could it be just my tuner? I am new to ESSB , so any suggestions would be great. I will change tuners this evening.
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Sounds like common mode interference or perhaps direct radiation from your antenna into your audio stuff.

    That's especially evident based on it not happening with a dummy load.

    What's your 40m antenna and how far away from the station is it?
    K0OKS likes this.
  3. W2KS

    W2KS Ham Member QRZ Page

    Thanks David. An OCF dipole up at 40 feet and then inverted V on both ends. 4:1 balun at the feedpoint....40 feet of vertical coax connected to a 1:1 line isolator, and then 125 feet of coax into my shack, which is in the basement. Not a problem on other bands, and not a problem on other radios connected to the same antenna.
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I'd add another 1:1 ferrite line isolator where the 125' of coax comes into the shack.

    Better still, a grounding type line isolator which not only uses ferrites internally to choke common mode but also grounds the outer conductor of the coax at the same time (it can be mounted to a well-grounded mounting plate just outside the hamshack wall):

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