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Re: [linrad] Fwd: [softrock40] Ver 7 28Mhz preamp? Yes

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  • Giancarlo Moda
    Hi all, the preamplifier at 28MHz is required when the VHF-SHF converter has a low gain and its output is designed for a higher gain IF like the one used in
    Message 1 of 3 , May 1, 2006
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      Hi all,

      the preamplifier at 28MHz is required when the VHF-SHF
      converter has a low gain and its output is designed
      for a higher gain IF like the one used in Linrad HDW
      or others.

      I would suggest to add the W7AAZ preamplifier using
      4xJfet in parallel, as used in the CDG2000 and
      Pic-A-STAR. This preamplifier has a very low noise
      (expected below 2dB)and another important aspect: The
      output impedance changes are no reflected to the input
      like for the Norton amplifier. It also has a high IIP3
      (>+35dBm).

      You may visit: http://www.warc.org.uk/ and look for
      the CDG2000 project.

      73

      Gian
      I7SWX




      --- w3sz <w3sz@...> wrote:

      > Hi, All,
      >
      > Just a note for those interested in using the
      > SoftRock v7.0 as a backend
      > for transverters, forwarded from the Yahoo Softrock
      > group.
      >
      > Unfortunately, he didn't provide details on what his
      > system actually was.
      > But it is still some information ;)
      >
      > As always, ymmv.
      >
      > I hope to start receiving my SoftRocks late this
      > week or early next week,
      > and then should have some reports for all.
      >
      > 73,
      >
      > Roger
      > W3SZ
      >
      > ------- Forwarded message -------
      > From: pxxxxxxxxis <bxxxx@xxxxxxx>
      > To: softrock40@...
      > Subject: [softrock40] Ver 7 28Mhz preamp? Yes
      > Date: Sun, 30 Apr 2006 19:07:48 -0400
      >
      > This morning I was using the Ver7 with my
      > 28/144Mhz receive
      > converter for a receive IF on 10Ghz rain scatter. I
      > tried the system
      > WITHOUT the 28Mhz preamp I have been using. I could
      > see nothing but a
      > few spikes in the 96Khz range. Added the 28Mhz
      > preamp again and the
      > 9-10db 10Ghz rainscatter signal from W0GHZ was easly
      > seen. .... 28Mhz
      > preamp REQUIRED for my system!
      >
      > Yahoo! Groups Links
      >
      > --
      > Roger Rehr
      > W3SZ
      > http://www.nitehawk.com/w3sz/
      >
      >
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    • KD5NWA
      I notice that the amplifier has a attenuation pad on it s output, rendering the impedance problem to be moot. I have some MMIC s that I m planning to
      Message 2 of 3 , May 2, 2006
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        I notice that the amplifier has a attenuation pad on it's output, rendering the impedance problem to be moot.

        I have some MMIC's that I'm planning to experiment with for the upper bands and use a SoftRock, since their gain is a little excessive I was planning on using a 3dB to 6dB pad, which will help setting the impedance of the filter at a more stable value

        At 03:24 AM 5/1/2006, you wrote:
        Hi all,

        the preamplifier at 28MHz is required when the VHF-SHF
        converter has a low gain and its output is designed
        for a higher gain IF like the one used in Linrad HDW
        or others.

        I would suggest to add the W7AAZ preamplifier using
        4xJfet in parallel, as used in the CDG2000 and
        Pic-A-STAR. This preamplifier has a very low noise
        (expected below 2dB)and another important aspect: The
        output impedance changes are no reflected to the input
        like for the Norton amplifier. It also has a high IIP3
        (>+35dBm).

        You may visit: http://www.warc.org.uk/ and look for
        the CDG2000 project.

        73

        Gian
        I7SWX




        --- w3sz <w3sz@...> wrote:

        > Hi, All,
        >
        > Just a note for those interested in using the
        > SoftRock v7.0 as a backend 
        > for transverters, forwarded from the Yahoo Softrock
        > group.
        >
        > Unfortunately, he didn't provide details on what his
        > system actually was.  
        > But it is still some information ;)
        >
        > As always, ymmv.
        >
        > I hope to start receiving my SoftRocks late this
        > week or early next week, 
        > and then should have some reports for all.
        >
        > 73,
        >
        > Roger
        > W3SZ
        >
        > ------- Forwarded message -------
        > From: pxxxxxxxxis <bxxxx@xxxxxxx>
        > To: softrock40@...
        > Subject: [softrock40] Ver 7 28Mhz preamp? Yes
        > Date: Sun, 30 Apr 2006 19:07:48 -0400
        >
        >     This morning I was using the Ver7 with my
        > 28/144Mhz receive
        > converter for a receive IF on 10Ghz rain scatter. I
        > tried the system
        > WITHOUT the 28Mhz preamp I have been using. I could
        > see nothing but a
        > few spikes in the 96Khz range. Added the 28Mhz
        > preamp again and the
        > 9-10db 10Ghz rainscatter signal from W0GHZ was easly
        > seen. .... 28Mhz
        > preamp REQUIRED for my system!
        >
        > Yahoo! Groups Links
        >
        > --
        > Roger Rehr
        > W3SZ
        > http://www.nitehawk.com/w3sz/
        >
        >
        #############################################################
        > This message is sent to you because you are
        > subscribed to
        >   the mailing list <linrad@...>.
        > To unsubscribe, E-mail to:
        > <linrad-off@...>
        > To switch to the DIGEST mode, E-mail to
        > <linrad-digest@...>
        > To switch to the INDEX mode, E-mail to
        > <linrad-index@...>
        > Send administrative queries to
        > <linrad-request@...>
        >
        >


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        Cecil Bayona
        KD5NWA
        www.qrpradio.com

        I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

      • Giancarlo
        ... upper ... the ... Hi Cecil, Regarding the W7AAZ Post-Mixer amplifier in the CDG2000 has a 50 ohm output for the very simple reason to permit a testing
        Message 3 of 3 , May 6, 2006
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          --- In softrock40@yahoogroups.com, KD5NWA <KD5NWA@...> wrote:
          >
          > I notice that the amplifier has a attenuation pad on it's output,
          > rendering the impedance problem to be moot.
          >
          > I have some MMIC's that I'm planning to experiment with for the
          upper
          > bands and use a SoftRock, since their gain is a little excessive I
          > was planning on using a 3dB to 6dB pad, which will help setting
          the
          > impedance of the filter at a more stable value
          >

          Hi Cecil,

          Regarding the W7AAZ Post-Mixer amplifier in the CDG2000 has a 50 ohm
          output for the very simple reason to permit a testing point. The
          4xJ310 output is 200 ohm. This would make an easier matching to the
          post amplifier xtal filter Zin = 500 ohm. The amplifier has around
          14dB gain and very low noise. The output IP3 is lower than expected,
          measured at +27dBm. Probably this is due to the changing input Z of
          following xtal filter. Adding an attenuator will reduce this effect
          and increase the OIP3 before the filter.
          I am sure that in the SoftRock an OIP3 of +27dBm of a preamplifier
          will be more than necessary.

          73

          Gian
          I7SWX
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