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Fw: Re: Fw: Re: [softrock40] Re: Bandpass filter smilter

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  • windy10605@juno.com
    Exactly ! I would much prefer an old tuneable WJ double tuned frontend ....but I don t have one, was going to adapt a Drake 2B preselector ...haven t done that
    Message 1 of 3 , Jan 30, 2006
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      Exactly ! I would much prefer an old tuneable WJ double tuned frontend ....but I don't have one, was going to adapt a Drake 2B preselector ...haven't done that either, and don't really want to plug and replug the BPFs as I scoot around the HF spectrum trying other things.
       
      Looking for the "least undesirable alternative".
       
      73 Kees K5BCQ
       
      ----- Forwarded Message -----
      From: KD5NWA <KD5NWA@...>
      Date: Wed, 01 Feb 2006 16:37:18 -0600
      Subject: Re: Fw: Re: [softrock40] Re: Bandpass filter smilter
       
      Not just odd and even multiples, it can respond to fractions 5/8....to keep unwanted signals, increased dynamic range, and keep the noise down you need a front end filter as tight as possible. Saying that however, for playing around mobility might be more important issue.

      The best of both is if you can find a multi-band front end filter unit (specially the double tuned) from 20 to 50 years ago, you can tune from 100KHz to 30MHz in one small box so you have mobility and better discrimination.

      I have one in a box in the garage, I've been searching for it, but I have not found it.

      At 03:49 PM 2/1/2006, joe price wrote:
      Disregard message below I cheched a 30mtr rx it responds to even  and
      odd harmonics need more testing.

      > I would expect that the SR40 would respond to even harmonics but mine
      > responds ONLY to odd multiples of the rx frequency I don't understand
      > why. Can someone else check this? The v5 rx uses a different QSD
      scheme
      > i'm not sure it's the same I will test and report result.
      >
      > Joe wa9cgz
      >







       
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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 ...

    • joe price
      ... the ... Kees, I just reconnected my test SD40 setup using DDS as 4x vfo although it will hear the even harmonic (way down) it s the odd that is
      Message 2 of 3 , Feb 1, 2006
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        --- In softrock40@yahoogroups.com, windy10605@... wrote:
        >
        > Exactly ! I would much prefer an old tuneable WJ double tuned frontend
        > ....but I don't have one, was going to adapt a Drake 2B preselector
        > ...haven't done that either, and don't really want to plug and replug
        the
        > BPFs as I scoot around the HF spectrum trying other things.
        >
        > Looking for the "least undesirable alternative".
        >
        > 73 Kees K5BCQ
        >

        Kees,

        I just reconnected my test SD40 setup using DDS as 4x vfo although it
        will hear the even harmonic (way down) it's the odd that is predominate.

        I set DDS to 4mhz for a receive frequency of 1mhz

        2mhz down 45 to 50db

        3mhz down 10db

        5mhz down 12db

        7mhz down 15db

        Joe
      • KY1K
        I think the even harmonics should not be a problem, as indicated. But, I thought the odd harmonics were supposed to be 6 db down for each step. I had a spice
        Message 3 of 3 , Feb 2, 2006
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          I think the even harmonics should not be a problem, as indicated.

          But, I thought the odd harmonics were supposed to be 6 db down for each step.

          I had a spice model once and I think (but cannot be positive) that I
          had confirmed this in Spice.

          But, suffice it to say that harmonics are a problem. In a superhet,
          the harmonics are converted out to non-existance....not so with the QSD.

          For a general coverage softrock, I would think a preselector would be
          the way to go....even though it would need to be tweaked every 100 to
          500 KHz (depending on the frequency of operation). A small price to
          pay (IMHO) for peace of mind and not having to wonder whether the
          signal you hear is actually there or is the result of an undesired
          harmonic response. Your mileage will vary.

          I would caution against automatic tracking varactor tuning. They have
          all the non linearity of crude mixers when exposed to large signals
          and the effects are well known to those who have tried to operate
          them in high rf environments.

          Maybe the group should be working on an all band preselector for the
          next generation softrock?

          Regards,

          Art



          At 06:07 PM 2/1/2006, you wrote:

          >--- In softrock40@yahoogroups.com, windy10605@... wrote:
          > >
          > > Exactly ! I would much prefer an old tuneable WJ double tuned frontend
          > > ....but I don't have one, was going to adapt a Drake 2B preselector
          > > ...haven't done that either, and don't really want to plug and replug
          >the
          > > BPFs as I scoot around the HF spectrum trying other things.
          > >
          > > Looking for the "least undesirable alternative".
          > >
          > > 73 Kees K5BCQ
          > >
          >
          >Kees,
          >
          >I just reconnected my test SD40 setup using DDS as 4x vfo although it
          >will hear the even harmonic (way down) it's the odd that is predominate.
          >
          >I set DDS to 4mhz for a receive frequency of 1mhz
          >
          >2mhz down 45 to 50db
          >
          >3mhz down 10db
          >
          >5mhz down 12db
          >
          >7mhz down 15db
          >
          >Joe
          >
          >
          >
          >
          >
          >
          >Yahoo! Groups Links
          >
          >
          >
          >
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