FT-991A 'HI SWR' when using ATU in 40m and lower bands

Discussion in 'Radio Circuits, Repair & Performance' started by PY2RAF, May 9, 2020.

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  1. PY2RAF

    PY2RAF XML Subscriber QRZ Page


    I would like to share an issue that happened to me today while using the ATU in 40m band.

    I was doing some tests in 7.290 and this is a bit off my antenna comfort zone - and I resorted to the ATU to put the radio in a comfortable operational envelope. The radio happily tunes - but when you transmit it brings the HI SWR flag.

    After some research, I found (not believing entirely) that this boils down to ATU board grounding pads covered with solder mask/lacquer. Guess what? It was indeed the case - and mine is a 2018 series FT-991A.

    I have documented the whole thing how to identify and fix in https://github.com/rfrht/FT-991A/wiki/Poor-Grounding-in-FT-991A-Tuner-Unit

    After fixing the grounding issue; I didn't even had to re-tune: I transmitted and got very low VSWR with the internal ATU - as expected.

    Hope this is of help; 73 de PY2RAF.
    PA5COR, KD2RCF and N2PQW like this.
  2. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    KD2RCF likes this.
  3. KD2RCF

    KD2RCF Ham Member QRZ Page

    Hi Rodrigo:

    Thank you for posting this !! My new FT-991a started having the "High SWR" problem... your description of the problem and fix is excellent ! Fixed my problem in 15 minutes !!

    Thank you, thank you, thank you !!

    '73 Don KD2RCF
    PY2RAF likes this.

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