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Re: [loopantennas] Re: Transmitting loop

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  • Steve Baker
    Whether or not you fry your output transistor, having that big standing wave really sucks... right? Yes....standing waves are hard to surf. ...
    Message 1 of 28 , Aug 2, 2005
      "Whether or not you fry your output transistor, having
      that big standing wave really sucks... right?"

      Yes....standing waves are hard to surf.

      --- Richards <jruing@...> wrote:

      > I am a novice just studying for the first exams....
      > I gather you
      > guys are in agreement on one thing...
      >
      > Whether or not you fry your output transistor,
      > having that big
      > standing wave really sucks... right?
      >
      > ///////////// Richards /////////////////
      > ===========================================
      >
      > dldorrance wrote:
      >
      > >Hank, thanks for the distinction. However, even if
      > the wave is
      > >re-reflected (back and forth around the speed of
      > light about
      > >
      >


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    • vze3v8dt@verizon.net
      Hello, Richards. Good luck with your studies. In general large SWR is a bad thing, however there are things that can be done to deal with it, some more
      Message 2 of 28 , Aug 2, 2005
        Hello, Richards. Good luck with your studies.

        In general large SWR is a bad thing, however there are things that can
        be done to deal with it, some more efficiently than others. Generally,
        a blanket statement about something excludes some possibilities which do
        work okay. An example with a high SWR is a center fed Zepp that is fed
        with twin lead transmission line, like 300 to 600 or more ohms
        characteristic impedance. At some frequencies there will be a good
        match between the antenna (load) and the transmission line. The next
        problem with that is that most rigs are set up with 50 ohm coaxial
        output (source impedance) so some method to convert from 50 ohms to 300
        - 600 ohms is needed. Sometimes people use baluns to do this, however
        they also have limitations and issues. For example, they introduce an
        extra loss element and at high power that generates heat, and so at high
        enough power levels with enough heat the ferrite or powdered core of a
        balun saturates causing the balun to become nonlinear and not work very
        well (as well as generating harmonics?). Maybe another way instead of
        using a balun is to use an antenna tuner (although most of them that
        have balanced line terminals also have baluns). I like my Johnson KW
        Matchbox tuner which doesn't have a balun and is quite efficient (at
        least on the "standard" (pre-WARC79) ham bands from 80 to 10m. Now,
        take for example an antenna impedance that is not the same as the
        characteristic impedance of the transmission line, then there is an
        SWR. The main problem with that is loss of signal in the transmission
        line as the reflected wave goes between from the antenna and the tuner
        and back again (and again and again ...). In coax this is a problem
        because the losses are high however using balanced feeders (twin lead)
        the losses are surprisingly small. So, it becomes an engineering
        problem, trying to minimize losses with tradeoffs of different
        architectures for a given design parameters. In general resonant
        antennas work very well and should be fed with coax or could be fed with
        balanced feeders and an appropriate impedance transformation at some
        point. Non-Resonant antennas should NOT be fed with coax (unless some
        tricks are done, I suppose), but would be better fed with balanced
        (twin-lead) feeders and use of a good "transmatch". Oh, by the way, the
        term "antenna tuner" is generally a false nomenclature unless it is
        actually employed at the end of the feedline at the antenna. However,
        most "antenna tuners" people use in their hamshacks actually help the
        transmitter match the load at that point. The only place there is a low
        SWR then is between the radio and the tuner, a matter of a few feet, but
        there could still be high SWR on the long run from the tuner to the
        antenna.

        You can learn a great deal more about this if you pick up a book called
        "Reflections" by Walt Maxwell, W2DU. He used to be the department head
        of the antenna group at a company that was at one time called RCA where
        communications and research satellites were developed and built. He
        retired before I was employed there in 1990, but it was evident that he
        was still greatly respected. The original version of the book was
        published by ARRL but later they ignored the science and tended to more
        folklore so they dropped his publication. It is again published in
        softcover as "Reflections II" and I think is in the 2nd or 3rd printing
        the last I knew and published now by WorldRadio Books.

        73,

        Mark, NK8Q


        Richards wrote:

        >I am a novice just studying for the first exams.... I gather you
        >guys are in agreement on one thing...
        >
        >Whether or not you fry your output transistor, having that big
        >standing wave really sucks... right?
        >
        >///////////// Richards /////////////////
        >===========================================
        >
        >dldorrance wrote:
        >
        >
        >
        >>Hank, thanks for the distinction. However, even if the wave is
        >>re-reflected (back and forth around the speed of light about
        >>
        >>
        >>
        >
        >
        >If you've got links, post them in the Links section!
        >http://groups.yahoo.com/group/loopantennas/links
        >
        >For uploading images, I prefer the Files section since Photos only allows everyone (except the uploader and moderators) to see a max of 300x400.
        >http://groups.yahoo.com/group/loopantennas/files
        >
        >Put them in the appropriate folder, or create one.
        >Yahoo! Groups Links
        >
        >
        >
        >
        >
        >
        >
        >
        >
        >


        [Non-text portions of this message have been removed]
      • dldorrance
        Richard, you must be a diplomat! Dave WA6YSO
        Message 3 of 28 , Aug 2, 2005
          Richard, you must be a diplomat!

          Dave WA6YSO

          --- In loopantennas@yahoogroups.com, Richards <jruing@a...> wrote:
          > I am a novice just studying for the first exams.... I gather you
          > guys are in agreement on one thing...
          >
          > Whether or not you fry your output transistor, having that big
          > standing wave really sucks... right?
          >
          > ///////////// Richards /////////////////
          > ===========================================
          >
          > dldorrance wrote:
          >
          > >Hank, thanks for the distinction. However, even if the wave is
          > >re-reflected (back and forth around the speed of light about
          > >
        • Richards
          Thanks... Henry... I liked that story. Kinda gets right to the heart of the sales pitch.... Are you from Missouri, ... the show me state? ...
          Message 4 of 28 , Aug 2, 2005
            Thanks... Henry... I liked that story. Kinda gets
            right to the heart of the sales pitch.... Are you from
            Missouri, ... the "show me" state? ...

            ////////////// JH Richards ////////////
            =================================

            Henry Kolesnik wrote:

            >While the rep was talking to another customer I was calling CQ on the 701 and I disconnected the antenna connector to verify what he said. He saw me doing it and tried to jump out of his skin trying to stop me, but he was too slow. He was somewhat shaken and upset and got a little testy with me but the 701 survived. I wouldn't have purchased one it didn't pass this test, and I bought one,
            >
            >
          • Richards
            WOW... THANK YOU FOR THE DETAILED REPLY. ///////// JH Richards ////////// ==================================
            Message 5 of 28 , Aug 2, 2005
              WOW... THANK YOU FOR THE DETAILED REPLY.

              ///////// JH Richards //////////
              ==================================

              vze3v8dt@... wrote:

              > Hello, Richards. Good luck with your studies.
              > In general large SWR is a bad thing, however there are things that can
              > be done to deal with it,
            • Richards
              Actually ... Worse than a diplomat.... I am a trial lawyer... (although I do not take injury cases...mostly business, criminal and divorce trial cases...)
              Message 6 of 28 , Aug 2, 2005
                Actually ... Worse than a diplomat.... I am a trial lawyer...
                (although I do not take injury cases...mostly business,
                criminal and divorce trial cases...)

                So... it is a rare instance that I play "diplomat!" Please do not
                tell anyone in my town - they will think I have gone soft...

                Thanks for poking some fun. //// JH Richards ///
                ==========================================

                dldorrance wrote:

                >Richard, you must be a diplomat!
                >
                >
                >
                >
              • Henry Kolesnik
                Tulsa, OK ... From: Richards To: loopantennas@yahoogroups.com Sent: Tuesday, August 02, 2005 11:10 PM Subject: Re: [loopantennas] Re: Transmitting loop
                Message 7 of 28 , Aug 3, 2005
                  Tulsa, OK
                  ----- Original Message -----
                  From: Richards
                  To: loopantennas@yahoogroups.com
                  Sent: Tuesday, August 02, 2005 11:10 PM
                  Subject: Re: [loopantennas] Re: Transmitting loop


                  Thanks... Henry... I liked that story. Kinda gets
                  right to the heart of the sales pitch.... Are you from
                  Missouri, ... the "show me" state? ...

                  ////////////// JH Richards ////////////
                  =================================

                  Henry Kolesnik wrote:

                  >While the rep was talking to another customer I was calling CQ on the 701 and I disconnected the antenna connector to verify what he said. He saw me doing it and tried to jump out of his skin trying to stop me, but he was too slow. He was somewhat shaken and upset and got a little testy with me but the 701 survived. I wouldn't have purchased one it didn't pass this test, and I bought one,
                  >
                  >


                  If you've got links, post them in the Links section!
                  http://groups.yahoo.com/group/loopantennas/links

                  For uploading images, I prefer the Files section since Photos only allows everyone (except the uploader and moderators) to see a max of 300x400.
                  http://groups.yahoo.com/group/loopantennas/files

                  Put them in the appropriate folder, or create one.



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                  [Non-text portions of this message have been removed]
                • RICH
                  For those interested in a commercially made Transmitting Loop antenna There is one available on the e-Place. It is made by ARA and is the ARA Model MLA1/E, 1.8
                  Message 8 of 28 , Aug 6, 2005
                    For those interested in a commercially made Transmitting Loop antenna
                    There is one available on the e-Place. It is made by ARA and is the
                    ARA Model MLA1/E, 1.8 MHZ to 15 MHZ, REMOTE CONTROLLED, 1000 Watts,
                    TX&RX VERT/HORIZ Item number: 796289675.

                    There a a lot of pictures and a good description. This along with the
                    ARA Catalog description/Specifications should give you a good idea of
                    the antenna.

                    RICH WA6KNW
                  • Richard M. MC Clung
                    The item number should be: 5796289675. Some how the first 5 was eliminated the first time I sent the info..... RICH WA6KNW From: RICH
                    Message 9 of 28 , Aug 8, 2005
                      The item number should be: 5796289675. Some how the first 5 was
                      eliminated the first time I sent the info.....
                      RICH WA6KNW

                      From: "RICH" <sgm460122@...>
                      Subject: Re: Transmitting loop

                      For those interested in a commercially made Transmitting Loop
                      antenna There is one available on the e-Place. It is made by ARA and
                      is the ARA Model MLA1/E, 1.8 MHZ to 15 MHZ, REMOTE CONTROLLED, 1000
                      Watts, TX&RX VERT/HORIZ Item number: 796289675.

                      There a a lot of pictures and a good description. This along with
                      the ARA Catalog description/Specifications should give you a good
                      idea
                      of the antenna.

                      RICH WA6KNW
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