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Re: [softrock40] Re: UK residents only

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  • leon Heller
    ... From: To: Sent: Wednesday, April 01, 2009 1:19 PM Subject: [softrock40] Re: UK residents only ... Below
    Message 1 of 5 , Apr 1, 2009
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      ----- Original Message -----
      From: <hsdx@...>
      To: <softrock40@yahoogroups.com>
      Sent: Wednesday, April 01, 2009 1:19 PM
      Subject: [softrock40] Re: UK residents only


      --- In softrock40@yahoogroups.com, Michael Fleetwood <mfleetwood@...> wrote:
      >
      > Hi,
      >
      > I am considering placing an order for a quantity
      > of Triad Magnetics SP70 600 ohm matching
      > transformers which have a 300 Hz to 100KHz
      > frequency response. If I get enough interest to
      > place an order, I can post them out to UK
      > addresses for £10 each or possibly less depending
      > on the size of the overall order.
      >
      > You can access a data sheet on them
      > here:
      > http://www.adrive.com/public/1bca76255dda40554e5ecfaa183a2e22d901fd7ab66252dccd6b87d3bd50c52a.html
      >
      > Please email me off list if you are interested.
      > Payment would be by cheque or Pay Pal.
      >
      > Mike G3XEF.
      >
      > Mike Fleetwood
      > Canberra Australia and Sidcup UK.
      >
      > Worldwide email address is: mfleetwood@...
      >
      Below 300Hz thay maybe non linear! above 300HZ you maybe ok but I tried two
      tx's out of old modems and they were both non linear causing the noise floor
      to go up and down across the spectrum in the SDR software. Good luck Steve
      2E0ZEH

      Those were isolation transformers designed for modems. The characteristics
      would have been different.

      Leon
      --
      Leon Heller
      Amateur radio call-sign G1HSM
      Yaesu FT-817ND transceiver
      Suzuki SV1000S motorcycle
      leon355@...
      http://www.geocities.com/leon_heller


      ------------------------------------

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    • Loftur Jónasson
      ... You may want to consider replacing the 0.1uF caps on the opamp outputs to 1uF. The raising of the noise floor you are most likely seeing in the low kHz
      Message 2 of 5 , Apr 1, 2009
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        >>
        > Below 300Hz thay maybe non linear! above 300HZ you maybe ok but I tried two
        > tx's out of old modems and they were both non linear causing the noise floor
        > to go up and down across the spectrum in the SDR software. Good luck Steve
        > 2E0ZEH
        >
        You may want to consider replacing the 0.1uF caps on the opamp outputs
        to 1uF. The raising of the noise floor you are most likely seeing in
        the low kHz range is due to ringing, resonance between the 0.1uF
        output capacitors and the inductance in the transformer. You may also
        be seeing a big dip below 1kHz. Larger caps, for instance 1uF, will
        rectify both.

        73 de Loftur, ve/tf3lj
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