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Re: [softrock40] Re: Radiation from the RX Ensemble II / what about antenna transformer?

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  • Alan
    ... Subject: Re: [softrock40] Re: Radiation from the RX Ensemble II / what about antenna transformer? ... Dave, Yes. The principle is that the grounded side
    Message 1 of 43 , Jul 17, 2012
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    ----- Original Message -----
    Subject: Re: [softrock40] Re: Radiation from the RX Ensemble II / what about antenna transformer?


    > OOPS -- I made the LO transformer change, but now I'm not sure what the
    > second transformer change is required on the Ensemble II Rx.
    >

    Dave,

    Yes.

    The principle is that the grounded side should go to the same end of the primary and secondary. The two wires that come from the
    same hole in the binocular core.
    On the Ensemble RX input transformer the primary ground is the shell of the plug.
    The secondary is grounded to RF by C37.
    So one of the windings needs to be fitted crossed.

    In actual fact it can be either winding that may be crossed.
    So for one that is already assembled the one that looks easiest to change may be used.

    To repeat Tony.
    Ensemble RX and Ensemble RXII:- T1 and T2 need one winding crossed.
    Ensemble RXTX T6 needs one winding crossed.
    VHF Ensemble T1 needs one winding crossed.


    73 Alan G4ZFQ
  • Alan
    But this discussion relates to radiation from the connecting cables. ... From: Peter To: Sent:
    Message 43 of 43 , Jul 19, 2012
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      But this discussion relates to radiation from the connecting cables.


      ----- Original Message -----
      From: "Peter" <pete@...>
      To: <softrock40@yahoogroups.com>
      Sent: Thursday, July 19, 2012 1:26 PM
      Subject: [softrock40] Re: Radiation from the RX Ensemble II


      > Many years ago I was involved in studying the "Zero-IF" receiver architecture (also called "direct conversion", "synchrodyne" and
      > "homodyne" for a military VHF application. Direct conversion ham receivers like the Neophyte common at the time, so I was struck
      > by one item that turned up in the study: Zero-IF receivers for critical applications almost always included some kind of RF
      > amplifier between the antenna and the mixer, even if gain wasn't needed. The amplifier provided reverse isolation, greatly
      > reducing LO radiation. For that reason and others I began including an amplifier ahead of the mixer in the Lazy Dog receivers.
      >
      >
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