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

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  • kc5kwz
    My little pea brain is having trouble catching on to the fix. Could someone please upload some pictures or drawings on the crossing of the seconday and primary
    Message 1 of 43 , Jul 18, 2012
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      My little pea brain is having trouble catching on to the fix.

      Could someone please upload some pictures or drawings on the crossing of the seconday and primary wires?

      Also a list of kits that are in need of the new wiring would be good to have.

      73

      KC5KWZ

      --- In softrock40@yahoogroups.com, "poxika" <jc@...> wrote:
      >
      > Tony,
      >
      > I'm building the ensemble rxtx, and tried to follow the discussion as much as I could. However, as a newbie, I do not understand what is meant by "crossing the secondary wires".
      > Does it means that the secondary wire should connect to the pad on the opposite side of the corresponding primary (e.g. left secondary connects to the pad aligned with right primary, right secondary connects to the pad aligned with left primary) ?
      >
      > Thanks,
      >
      > JC
      >
      > --- In softrock40@yahoogroups.com, Tony Parks <kb9yig@> wrote:
      > >
      > > Good Morning Alan,
      > >
      > > Yes, my intent is to change the board artwork for the RX Ensemble II,
      > > the RXTX Ensemble and the 6m/4m/2m RX Ensemble so that the transformers
      > > for the Si570 output coupling and the unit antenna coupling each have
      > > the ground sides on the same side of the core. This will result in two
      > > transformer wiring changes for the RX Ensemble board, one wiring change
      > > for the RXTX Ensemble board, and one wiring change for the 6m/4m/2m RX
      > > Ensemble board.
      > >
      > > Presently I have a good supply of the circuit boards in stock so it will
      > > be a few months down the line before these changes get into production
      > > circuit boards. I hope people do not mind crossing the secondary wires
      > > in mounting the transformers.
      > >
      > > Thanks always for the help you and others give to make the SoftRock kits
      > > fun and useful for people.
      > >
      > > 73,
      > > --
      > >
      > > Tony Parks
      > > kb9yig@
      > > http://www.kb9yig.com
      > >
      > >
      > >
      > >
      > > On Tue, 2012-07-17 at 13:29 +0000, Alan wrote:
      > >
      > > >
      > > >
      > > >
      > > > ----- Original Message -----
      > > > Subject: [softrock40] Re: Radiation from the RX Ensemble II / what
      > > > about antenna transformer?
      > > >
      > > > >
      > > > > I do not suspect changing the ANTENNA transformer in the RXTX will
      > > > have much effect on LO fundamental radiation. There were two
      > > > > separate issues addressed in my tests:
      > > >
      > > > Warren,
      > > >
      > > > The tests I made were of the LO transformer and confirmed what you and
      > > > Gerhard have found. But they were done under actual operating
      > > > conditions.
      > > >
      > > > No, the antenna transformer will not affect LO radiation.
      > > > I was speculating how much difference this transformer would make in
      > > > practice and how we can check.
      > > >
      > > > I suspect in my setup there will be little difference. But I have a
      > > > set of 3 ground rods buried within 10 ft of me.
      > > > Your description of your QTH brings me down to ground! I now
      > > > understand that what you said could be true. Without knowing your
      > > > situation I admit I was thinking you were exaggerating.
      > > > I was not disputing that new builders should ensure they are wired
      > > > correctly. But I was wondering how strongly we should advise
      > > > anyone who has a completed Ensemble to dismantle it to change either
      > > > transformer. Many Ensembles have been built and I until
      > > > Gerhard's post I was not aware of any complaints that point to these
      > > > transformers.
      > > > From what you say anyone in a situation anything like yours should
      > > > change the antenna transformer connections of the Ensemble RXTX.
      > > >
      > > > Tony has said he will change the Ensemble RX but so far has made no
      > > > comment about the RXTX version.
      > > >
      > > > 73 Alan G4ZFQ
      > > >
      > > > >
      > > > > 1) Radiation of LO fundamental from an RXII due to the polarity on
      > > > T!, the transformer that couples the USB to the main board.
      > > > >
      > > > > 2) Radiation by the output coax shield while transmitting normally
      > > > from an RXTX due to a similar mis-polarity on T6, the antenna
      > > > > transformer of the RXTX. By inference this radiation might also be
      > > > taken as a measurement of unwanted signal pickup on the coax
      > > > > shield when the RXTX is in receive mode.
      > > > >
      > > > > My attempt was to quantify the change in each case when the
      > > > transformer was reversed.
      > > > >
      > > > > To answer your question specifically about a good ground being
      > > > applied to the coax output connector I would say it would be like
      > > > > chicken soup.... "it couldn't hurt!". Seriously, I think it would
      > > > reduce the difference between the two transformer states, maybe
      > > > > even eliminate it. As an 18th floor apartment dweller I don't have a
      > > > ground in which I am confident and this is undoubtedly the
      > > > > source of lots of mischief in my shack.
      > > > >
      > > > > I think the bottom line on this will be us all coming to the
      > > > conclusion that the two transformers are best installed with the
      > > > > secondaries reversed. As you know, good operating practices like
      > > > proper grounds can cover for a lot of shortcomings.... but it is
      > > > > best not to rely on them. I am not an engineer and I don't profess
      > > > to fully understand why it is important to have such
      > > > > transformers properly phased. However I think I do now understand
      > > > the very practical effects of getting it backward.
      > > > >
      > > > > One final thought: I have no evidence that changing the antenna
      > > > transformer on the RXTX did anything to improve the performance of
      > > > > the transceiver itself. What it does seem to have done is lower the
      > > > noise floor of the antenna/feedline/radio combo by at least 10
      > > > > dB which seems to be "uncovering" signals that I could not decode or
      > > > even see before.
      > > > >
      > > > > Hope that answered the question.
      > > > >
      > > > > Warren Allgyer - W8TOD
      > > > >
      > > > >
      > > > >> Has anyone any ideas on a "real world" test of the antenna
      > > > transformer?
      > > > >> I suspect results will be variable according to an individual
      > > > setup.
      > > >
      > > >
      > > >
      > > >
      > > >
      > >
      >
    • 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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