SWR Problem?

Discussion in 'General Technical Questions and Answers' started by N1QWI, Oct 21, 2020.

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  1. N1QWI

    N1QWI Ham Member QRZ Page

    Hi everyone,

    I have been changing my antenna configuration a bit for use with my Yaesu FT 450 D. I use an end fed half wave HFedz antenna.

    It is in an inverted L configuration and I recently moved the antenna higher. As the designer states, the antenna tunes best when the feed point is at least 8 feet above the ground. It is now probably about 13 feet up.

    I also recently attached a ground to the outside shield of the coax where it meets the earth coming down from the feed point along a tree.

    Now here is the problem: when I tune up, the SWR states 1:1 while tuning with my tuner, but then when I key the transmitter, the SWR can be as high as 2:1.

    I am not positive but I think this started when I installed the ground rod. It could also have been after I spliced the wire back together after it snapped during a windstorm. I doubt that the latter would cause the problem though.

    any thoughts?
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    First thought is the tuner does not remain engaged when you transmit and not "tuning."
  3. KD0CAC

    KD0CAC Ham Member QRZ Page

    Possibly arcing when TX-ing
  4. KP4SX

    KP4SX Premium Subscriber QRZ Page

    If you're using very low power for tuning its not unusual to see a different SWR reading at full power if your meter is not linear.
  5. N1QWI

    N1QWI Ham Member QRZ Page

    I am using the internal tuner from the radio. I hope that’s not the problem!
  6. WA0CBW

    WA0CBW Ham Member QRZ Page

    How do you tune up without the transmitter? You said you tune up but when you use the transmitter the SWR is higher.
  7. K8JD

    K8JD Ham Member QRZ Page

    This is why I prefer nice, stable, coax fed dipoles :D
    AI3V likes this.
  8. N1QWI

    N1QWI Ham Member QRZ Page

    So I ran an antenna analyzer to the feed line at the transmitter end.

    I now understand that the SWR has changed because my configuration of the antenna changed after a recent windstorm. The transmitter is not the problem! I believe that because the feed point is not making a 90° angle between the coax and the transformer, this is to blame. On top of that, the inverted L is not 90° Bent either. It is more like 110. Looks like I need to try to change the antenna back to how it was before!
  9. WA9UAA

    WA9UAA Ham Member QRZ Page

    Add more ground wires and use the tuner in the radio, there is not much loss at 2:1 VSWR.
  10. AA5MT

    AA5MT Ham Member QRZ Page

    Long forgotton, easily overlooked problem(maybe)

    A user has a mobile antenna which works well. Trying to save money, he decides to move the antenna to his house.

    Before doing this, he checks everything in the car with his analyzer and swr meter for a comparison. He puts the antenna on the house. He checks it with the analyzer and everything looks fine. But, when he put the radio on the antenna, the swr is through the roof! What happened?

    He put it back on the swr analyzer and it still looked good. He finally figured out that the station was grounded. When he grounded the analyzer, the swr shot up. The problem was that he grounded the system. Once he figured this out, he isolated the power supply ground, and the antenna became operational.

    Since the antenna worked before the storm, you may have a broken line, such as the ground wire.


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