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Tuner problems? (LDG Z-100Plus)

Discussion in 'General Technical Questions and Answers' started by W6DOZ, May 16, 2021.

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  1. W6DOZ

    W6DOZ Ham Member QRZ Page

    Good evening everyone. I have recently run into a problem and was wondering if anyone could offer any advice. I currently use an LDG Z-100Plus Autotuner with my FT-891. I run a horizontal wire antenna in an NVIS configuration. I have never run into any problems with my Z-100Plus tuner not working. Randomly today, the tuner will no longer find a solution for an SWR tune. It sounds like the latches are working, yet the radio continues to report excessive SWR. The tuner completes the tuning process; however, it does not find a solution.

    Nothing has changed with my setup. I checked the following to try and discover what the problem was:

    1. I did check to make sure the coax feedline was connected and secure. I also checked the state of the coax feedline and did not locate any damage. The feedline was securely attached to the antenna transformer.
    2. I checked to make sure the feedline was securely attached to the wire antenna transformer unit.
    3. I checked to make sure the wire antenna and counterpoise were properly connected to the transformer unit.
    4. I checked the health of the battery powering the Z-100Plus tuner.
    5. I attempted a long button press on the tuner to initiate a full tune, not from memory.

    After checking all of the above, I still cannot get the tuner to find a solution.

    To continue working on my contacts for the night, I attached a 300 Ohm termination resistor to the end of the antenna wire, changing my configuration into a sloping wire configuration. I still get excessive SWR, which should not happen. When I put the tuner in bypass mode still get excessive SWR. When I plugged the antenna feed line directly into my FT-891, the SWR is back to an acceptable level.

    Any help would greatly be appreciated.

    Thank you!
  2. KL2WX

    KL2WX Premium Subscriber QRZ Page

    My Z100 Plus seems less finnicky when I ground the chassis of the radio to the tuner.
  3. KA2RRK

    KA2RRK Platinum Subscriber Platinum Subscriber QRZ Page

    Your experiencing the same problem with the LDG Z-100 Plus
    tuner that I have seen with my particular unit. I have tried every form of test I could, with various precision loads well within it's rated range and power and failed to perform. And it refuses to do much of anything else but make noise and flash it's indicators. Totally unreliable in holding a matched condition if at all. I suspect that the relays are flamed out. I aquired my unit used, so who knows what it has been subjected to as far as any former abuses...

    My resolution is rightly back to my trusted old manual tuner.
    Which has never been a problem. Other than being @ least 6 times bigger in size.

    WD4ELG likes this.
  4. W6DOZ

    W6DOZ Ham Member QRZ Page

    I will give this a try!
  5. W6DOZ

    W6DOZ Ham Member QRZ Page

    I think you’re on to something there. Use a manual tuner. I guess you can’t go wrong with that.
  6. KA2RRK

    KA2RRK Platinum Subscriber Platinum Subscriber QRZ Page

    Well, one test was using my IFR-1200 as a precision load. And the RF power input set to 10 watts @ 14.250mhz. It is in good working order and measures power very well. I used my Icom IC-7000 as a source set to 10 watts FM for convenience. This was a reference point during tests. A MFJ-225 VNA was used to confirm that the load was the right size was near what we wanted.

    My testing was for between 2.5watts and 25 watts. And probably a range of 5 to 250 ohms crudely measured with a MFJ-225 VNA.

    With a test jig MADE UP with back to back 4:1 BALUNS and short lengths of rg-58 jumpers along wit a few of fixed value caps and test lead jumpers up to 30 inches used to intentionally disturb the match conditions. Simulation of doing all the wrong things, within a certain limit... Otherwise having Fun.

    During this test I felt comfortable with remaining below 25watts of power level due to the couple hundred volt flat pack ceramic RF rated caps used and test leads thrown in, on, around the test bench... Testing done @ night time so minimal concerns to being a QRM source...

    All tuning operations of both were done @ 2.5 watts RF level.
    And power tests were held to below 25watts. Duty cycle testing
    was conducted of 2min on and 6min off @ 25watts.

    The tuner war was begun. I tested both on several night sessions in this way. Because the Z-100 Plus was displaying unstable operations.

    The manual tuner won in every instance. Reliable in providing the source with a 50 ohm match. And took all power levels. Everytime. It is a .5KW class unit.

    The Z-100 Plus was unable to provide the source with a match
    Reliable with any load presented to it. It would tune occasionally.
    Then if I you changed input power it would fail immediately or soon after. Sometimes just leaving it alone, and sitting idle after it matched some value of load, it would fail upon a short load test @ it's tune power level. Because of this repeated occurrence no duty cycle tests were attempted upon this unit.

  7. W6DOZ

    W6DOZ Ham Member QRZ Page

    I was really hoping this would be the issue. I replaced the ground link wire between the tuner and radio and same behavior. Doh! Oh well. I think I'm just going to go to manual tuners. Too many things to go wrong/break with the auto tuners.
    KA2RRK likes this.

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