FT-991A MODS VHF UHF ???

Discussion in 'Amateur Radio Equipment Reviews' started by IZ7FTU, Apr 3, 2018.

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  1. IZ7FTU

    IZ7FTU QRZ Member

    hello, I wanted some information on the ft-991a, the just bought I wanted to know how to do the bandwidth expansion on vhf uhf, I found they are like expanding the hf doing jp3003 jumper, instead I do not find how to expand the vhf uhf now the radio in tx 144-146 mhz there is a way to go in tx up to 148mhz, perhaps because the European version? I ask you for help as I wait for your answer. Thank you.
     
  2. IZ7FTU

    IZ7FTU QRZ Member

     
  3. KC8QVO

    KC8QVO Ham Member QRZ Page

    The US version has 2x resistors, they appear anyway, in JP3001 and JP3002. They are marked with "000". The mods.dk site shows solder bridges in these places. I assume the "resistors" are 0 ohms. I tested continuity across them.

    I do not know if this will expand the VHF coverage or if there is something else in the radio/software that affects it. You may check the firmware in the radio. There are updates available. The US version of the yaesu website has the downloads for the software updates (NOTE: there are different ones for the FT-991 and the FT-991A. I made that mistake and bricked the rig with the FT-991 version on an FT-991A, then realized my mistake and went through the flashing process again - radio works fine now).

    Check the thread I created on this for more notes:
    https://forums.qrz.com/index.php?threads/ft-991a-expanded-tx-on-vhf-uhf.623521/
     
  4. KX2U

    KX2U Ham Member QRZ Page

    Has anyone successfully modified the 991a or 991 to transmit outside the ham bands?
     
  5. PA5COR

    PA5COR Ham Member QRZ Page

    Not possible, VHF and UHF band edges for transmit are software defined in the FT991 and FT 991A.
    Depending on to where the radios are exported band edges are set for that region.
    See difference in 2/70 bands EU and USA.
     
    Last edited: Jan 30, 2021
  6. KX2U

    KX2U Ham Member QRZ Page

    If its defined in software than someone should be able to hack it eventually.
     
  7. PA5COR

    PA5COR Ham Member QRZ Page

    For what goal exactly?
    I'm not planning to transmit out of the bands, receive already goes far enough.
     
  8. KX2U

    KX2U Ham Member QRZ Page

    The goal is to push the equipment past its designed parameters. Part of the hobby....
     
  9. PA5COR

    PA5COR Ham Member QRZ Page

    not for me, i rather keep the radio within specifications and working well.
    Fine for you to do, your radio, but i never transmit out of band by choice.
    Not even in an dummy load.
     
    KK5UP and KU3X like this.
  10. N3FAA

    N3FAA XML Subscriber QRZ Page

    It absolutely is. Using non type-accepted equipment where type-accepted radios are required, is not.
     
    KA9JLM likes this.

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