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Re: [BCD396XT] Re: A better understanding of P25 decoding

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  • Tony Langdon
    ... Don t forget polarisation. Most, if not all of the signals of interest to people in the group here are going to be verticaly polarised, because that makes
    Message 1 of 17 , Feb 12, 2013
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      On 13/02/13 3:12 PM, Michael Hopkins wrote:

      > Sorry, but I have to take issue with John Stark’s comments about grounding a Yagi. Any Yagi will work with a scanner or hand held tranciever without being grounded. What IS important is that you use good quality coax as John suggests and that the coax braid is properly connected to the yagi and the scanner.
      Don't forget polarisation. Most, if not all of the signals of interest
      to people in the group here are going to be verticaly polarised, because
      that makes it easy to use a simple vertical antenna for mobile
      stations. That means any Yagi needs to be mounted "on its side", and
      not "flat" like a TV antenna. The loss caused by this cross
      polarisation can exceed 20 dB, and the radiation pattern is likely to be
      all over the place, increasing the likelihood of reflections corrupting
      the received signal, especially when receiving digital transmissions.

      --
      73 de Tony VK3JED
      http://vkradio.com
    • Michael Hopkins
      Tony --- you are absolutely correct. Most of what we listen to on a scanner is vertically polarized so anyone using a yagi should definitely mount it so the
      Message 2 of 17 , Feb 13, 2013
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        Tony --- you are absolutely correct. Most of what we listen to on a scanner is vertically polarized so anyone using a yagi should definitely mount it so the elements are vertical. Personally, I use a discone antenna which is broadband from about 100MHz to 1GHz, vertically polarized and omnidirectional. I have two of them: one at home on a 30 foot mast, and one at the cabin in main just stuck up in a crawl space about 20 feet above the ground. Both work exceptionally well.



        Cheers,





        Mike Hopkins – K1VLB

        Mhopkins735@...



        From: BCD396XT@yahoogroups.com [mailto:BCD396XT@yahoogroups.com] On Behalf Of Tony Langdon
        Sent: Wednesday, February 13, 2013 2:02 AM
        To: BCD396XT@yahoogroups.com
        Subject: Re: [BCD396XT] Re: A better understanding of P25 decoding





        On 13/02/13 3:12 PM, Michael Hopkins wrote:

        > Sorry, but I have to take issue with John Stark’s comments about grounding a Yagi. Any Yagi will work with a scanner or hand held tranciever without being grounded. What IS important is that you use good quality coax as John suggests and that the coax braid is properly connected to the yagi and the scanner.
        Don't forget polarisation. Most, if not all of the signals of interest
        to people in the group here are going to be verticaly polarised, because
        that makes it easy to use a simple vertical antenna for mobile
        stations. That means any Yagi needs to be mounted "on its side", and
        not "flat" like a TV antenna. The loss caused by this cross
        polarisation can exceed 20 dB, and the radiation pattern is likely to be
        all over the place, increasing the likelihood of reflections corrupting
        the received signal, especially when receiving digital transmissions.

        --
        73 de Tony VK3JED
        http://vkradio.com





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