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Re: [GEO-Subscribers] Best coax?

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  • Andy Eskelson
    There are a couple of common cable numbers, RG is one and UR is another UR67 was foir a long time the most common thick coax used in Amateur Radio. Mainly
    Message 1 of 11 , Jan 17, 2013
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      There are a couple of common cable numbers, RG is one and UR is another

      UR67 was foir a long time the most common "thick" coax used in Amateur
      Radio. Mainly because it could handle the high power.

      RG231 is an enhanced spec of that type of cable. Another is Westflex 103

      However that's all for transmitting. CT100 is good for receivinbg.
      it's loss is about 9db/100m at 200Mha, 7db at 100Mhz

      However plain old RG6 HF TC coax is a bit better better. 2db /100 ft at
      100Mhz, and 6db at 1Ghz

      If the impedance is mismatched then you will get a loss, but with ATP
      the signals are quite large so the loss is not that important.

      A Turnstile is most def. a balanced form of antenna, a dipole cannot be
      anything else. Coax is unbalanced so there is a matching arrangement to
      convert. Just connecting the coax is often enough!.

      The Rx is designed with a 50ohm input in mind, so for best results
      that's what the antenna and coax should be. However in practise you will
      be unlikely to notices any real difference in this application.

      Always remember that the sats are line of sight signals. It makes no
      difference if you shove the antenna up on a pole or tie it to a chair
      in the garden providing the antenna can see the sat. So it's always
      worth taking a few passes with the antenna at ground level first so that
      any tweaks can be done .

      Andy






      On Thu, 17 Jan 2013 10:02:42 -0500 (EST)
      geojohnt@... wrote:

      >
      > In a message dated 17/01/2013 08:32:49 GMT Standard Time,
      > gm8arv@... writes:
      >
      > For 20m I would try and get something better than RG58 - its loss is
      > around
      > 3.8 dB. Probably the best value for money low-loss cable is good satellite
      > TV cable - its lower loss will more than compensate for the slight loss
      > caused by impedance mismatch.
      >
      >
      > All,
      >
      > Not being a radio ham I'm not familiar with 'RG' cables and their
      > properties.
      >
      > With modern satellite TV the standard (good spec) cable was CT 100 -
      > though I think this is now CT 125?
      > Good screening and low loss.
      >
      > However, David raises a good point - impedance matching.
      > I seem to remember someone saying sometime ago that impedance matching was
      > only really important when transmitting.
      > 50 and 75 ohm being close enough for receiving - and (most) turnstile
      > antennas are unbalanced anyway.
      >
      > Also I'm not sure what the R2ZX expects to 'see' at the antenna input?
      >
      > I hope my comments will generate some enlightening information - for me, at
      > least.
      >
      > Regards,
      > John.
      >
      >
      >
      >
      > [Non-text portions of this message have been removed]
      >
    • David J Taylor
      From: Andy Eskelson [] However that s all for transmitting. CT100 is good for receivinbg. it s loss is about 9db/100m at 200Mha, 7db at 100Mhz However plain
      Message 2 of 11 , Jan 18, 2013
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        From: Andy Eskelson
        []
        However that's all for transmitting. CT100 is good for receivinbg.
        it's loss is about 9db/100m at 200Mha, 7db at 100Mhz

        However plain old RG6 HF TC coax is a bit better better. 2db /100 ft at
        100Mhz, and 6db at 1Ghz
        []
        Andy
        =======================================================

        There's a helpful chart for TV type cables here:

        http://www.satcure.co.uk/tech/cablespecs.htm

        I've found SatCure to be a very helpful, prompt, and reasonable cost
        supplier of cables, connectors, and all sorts of accessories. Highly
        recommended! (No, I still hate F connectors!) 30m of WF100 is £15, 50m is
        £21:

        http://www.satcure.co.uk/accs/WF100_cable.htm

        Many of the transmitting cables marketed for Amateur Radio use are well over
        £1 per metre.

        73,
        David GM8ARV
        --
        SatSignal Software - Quality software written to your requirements
        Web: http://www.satsignal.eu
        Email: david-taylor@...
      • David J Taylor
        Hi all, I have just purchaced a new r2zx and a turnstile antenna from the geo shop. I am upgrading from a very old timestep reciver and a homemade qfh. I
        Message 3 of 11 , Jan 28, 2013
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          Hi all,

          I have just purchaced a new r2zx and a turnstile antenna from the geo shop.
          I am upgrading from a very old timestep reciver and a homemade qfh.

          I curently use rg213 coax with my old timestep but wondered what you
          experianced guys would recomend for use with the r2zx. I intend on using my
          homemade qfh on one antenna input and the new turnstile on the other.

          Thanks.

          Matt
          ===================================

          Matt,

          If you are on a tight budget, you can use satellite TV cable. In spite of
          the slight impedance mismatch, to total loss over a long length may be less,
          and it's a lot cheaper than RG213.

          http://www.satcure.co.uk/accs/page8.htm

          30m reel £15

          http://www.satcure.co.uk/accs/WF100_cable.htm

          [Sorry for the delay in this message, it must have been your first post and
          Yahoo had a hiccup at the instant it was approved. Your subsequent posts
          won't need approval.]

          Cheers,
          David
          --
          SatSignal Software - Quality software written to your requirements
          Web: http://www.satsignal.eu
          Email: david-taylor@...
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