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19630Re: [GenesisRadio] RE: TX image supression failure

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  • Bruce kf1z
    Feb 20, 2014
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      Is the software phase and gain still set to zero?
      The "sweet spot" of the null would be very narrow...
      However you would have at least 2 turns on either side where you would see movement.
      If the display you are using only refreshes say once every second, then a turning speed of the pot
      of around 1/4 turn per second should be ok.
      The "main carrier" is not the "LO" .The main carrier is at the freq set by VFOA, which is always different than the LO freq.
      On your ftdx display can you see all three at once?  ( VFOA, LOsc, and image?)
      Sent: Thursday, February 20, 2014 10:23 AM
      Subject: Re: [GenesisRadio] RE: TX image supression failure

      I have no problem with LO at all - it's down from my second adjustment using Agilent E4420B spectrum analyzer as reference. It was really easy - just following instructions and  it's done! After that I found a brick wall on my way trying to adjust TX image. It possible that I am doing it wrong... What is the turning rate when adjusting trim pot? Is the "null" dip very narrow and easy to miss? I also understand that FTdx-3000 panadapter really slow for that job and will try to use spectrum analyzer again. I do not see any change on main carrier (LO) when adjusting IR trim pot - it stays suppressed and does not show up on the screen. Level of the image does not change and shows around 8-10dB down from fundamental.


      Oleg Gorelov KF5QCO

      ---In GenesisRadio@yahoogroups.com, <kf1z@...> wrote:

      Not what I meant....
      Your message made it sound like 'because of' a clean install of GSDR. you couldn't do TX image null.
      Does the level of the image change at ALL?
      Does the main carrier change when adjusting the IR pot?
      I assume you can see the main carrier, the LO, and the image on the ftdx3000 all at the same time?
      Sent: Thursday, February 20, 2014 5:59 AM
      Subject: Re: [GenesisRadio] RE: TX image supression failure

      No, I did not try do TX IR without software (is it possible to transmit on SDR without software?). My statement is I cannot do TX IR with "fresh" or old setup - it is not installation problem. Once I had it down from 5dB to 10dB, all my attempts to repeat this simply failed. I also can check DC points quick - I have only DMM at home and can use a panadapter on FTdx-3000 for reference. At work I have all professional equipment I need, including spectrum analyzer, but very limited on time use. I would like to have a clear plan what to do before I bring my radio to work and start getting too much attention from upper management.

      Oleg Gorelov KF5QCO.

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