FT450D SDR Panadaptor

Discussion in 'Software Defined Radio (SDR)' started by M0KLG, Jan 23, 2019.

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  1. M0KLG

    M0KLG XML Subscriber QRZ Page

    Hi Guys, just finished building an auto RF sensing (and Manual ptt for backup) antenna switch, so I can use my RTL/SDR as a panadaptor without opening up my rig.

    Basically internals are a modified QRP-Kits Easy TX switch.

    Hope you like.



    All The Best



    2E0CIT likes this.
  2. G0VKT

    G0VKT Ham Member QRZ Page

    I need one of those. Any links to the build?

    I also run the same radio as you and have just bought an RSP1a


  3. M0KLG

    M0KLG XML Subscriber QRZ Page

    Email me (I'm good on QRZ) and I will send you the circuit diagram and some build notes as soon as I have written them.



  4. M0KLG

    M0KLG XML Subscriber QRZ Page

    After bench testing, I finally plugged it all in and it works perfectly (well almost).................
    I realise that due to the configuration I am probably presenting 25 ohms to the rig and the SDR on receive (due to splitting the antenna feed between both of them at the same time).
    In transmit mode only the rig is connected to the antenna (albeit through the rest of the internal circuitry as well). So it shoud be seeing 50 Ohms.
    I have an inch of coax (internally) between the antenna and the rig SO259's to give a permanent rig to antenna connection.

    With the power off is the SWR has gone very squirrely, it is very difficult to get a good match even with a manual tuner.

    What am I doing wrong?

    I don't want to leave the switch permanently switched on as I am mainly using FT8 at the moment due to Plasma TV RFI from my neighbour which makes SSB difficult for 20 hours a day.

    Any advice greatly appreciated as this has gone way above my pay grade.

    Rob 2E0WRD

  5. G0VKT

    G0VKT Ham Member QRZ Page

    Email sent.

    Without seeing the circuit I can only guess that part of the switch is still in circuit which affects SWR.

    Why can't you just leave it powered up. Like the MFJ unit?

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