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.
    WD9E, K2GFI, KH2BR and 3 others like this.
  2. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    K0UO and KD2RCF like 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.
  4. KJ7AFR

    KJ7AFR Ham Member QRZ Page

    Does anyone know if Yaesu will fix this under warranty?
  5. N1RND

    N1RND Ham Member QRZ Page

    I just bought a new 991a less than a week ago. Haven't used the tuner much, but I'll have to test mine.
  6. KJ7AFR

    KJ7AFR Ham Member QRZ Page

    My FT991a is about an year old. It did not have this problem to start with, but seems to have developed it over the last couple of months.
  7. N1RND

    N1RND Ham Member QRZ Page

    Really, I wonder if that's going to happen to mine.
    How about star washers under the screws.
  8. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Yaesu and warranty = sending it to the service center good luck on that one.
    How they get away with calling the service center I don't know
  9. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    I personally don’t like the star washer approach - just adds yet another middleman between the board and the grounding pad.

    Just remove the lacker from the board and you’ll be fine.

    Direct and good contact.
    PU2OZT likes this.
  10. WD9E

    WD9E Ham Member QRZ Page

    Today I performed this fix on my 2019 FT-991A. The hi SWR on 40m completely vanished. So happy I didn't have to send it into Yaesu's service center.
    PY2RAF likes this.

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