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Re: [loopantennas] REALLY dumb question from a non radio guy.

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  • Jim Dunstan
    ... The radio more than likely uses a ferrite rod antenna/front end inductor. If it has a terminal for the AM receiver it will in all likely hood be connected
    Message 1 of 10 , Aug 8, 2004
      At 04:01 PM 8/7/04 +0000, you wrote:
      I just bought a Sangean PRD-2 radio.  It works great on the internal
      AM antenna.  Just for experimentation, I want to hook up an external
      loop antenna.  It has 2 terminals on the back.  One marked "am
      antenna" and the one next to it marked "ground".  My question is,
      where do the 2 wire leads from the antenna go?  I assume the ground
      is for a ground wire and not the antenna.  Do the 2 wire leads from
      the antenna both go to the terminal marked "am antenna"?  What?                                 
       
      The radio more than likely uses a ferrite rod antenna/front end inductor.  If it has a terminal for the AM receiver it will in all likely hood be connected to a wire link wound around the ferrite rod.  In this case you have 2 choices for coupling to a tuned loop.

      1.  Simply ignore the connectors and making a physical connection between the loop and the radio.  Tune the radio to the frequency of your choice, then tune the loop to the same frequency and orient the loop and radio for best reception.

      2.  If your loop has a pair of wires coming out (usually from a coupling link) then simply connect one wire to the 'AM Antenna' connector and the other to the one marked 'ground'.  If the wire from the loop is a coax type wire, then connect the centre conductor to the 'AM Antenna' connector and the shield to the 'Ground' connector.

      Experiment with both methods.



                     

      Jim Dunstan
      Thunder Bay, ON

    • realrussian
      OK, I hooked the loop (a cheap, simple little plastic thing that comes with an am/fm hifi receiver for the am part) up 1 wire to am antenna and 1 wire to
      Message 2 of 10 , Aug 9, 2004
        OK, I hooked the loop (a cheap, simple little plastic thing that
        comes with an am/fm hifi receiver for the am part) up 1 wire to "am
        antenna" and 1 wire to "ground". I tuned to a strong local station.
        When I rotated the loop for strong signal it sounded about like the
        internal ferrite bar. But, when I rotated to null the station signal
        I got nothing. Does this indicate that something automatically
        disconnects the internal ferrite bar when I have the loop hooked up?


        --- In loopantennas@yahoogroups.com, Jim Dunstan <jimdunstan@r...>
        wrote:
        > At 04:01 PM 8/7/04 +0000, you wrote:
        > >I just bought a Sangean PRD-2 radio. It works great on the
        internal
        > >AM antenna. Just for experimentation, I want to hook up an
        external
        > >loop antenna. It has 2 terminals on the back. One marked "am
        > >antenna" and the one next to it marked "ground". My question is,
        > >where do the 2 wire leads from the antenna go? I assume the ground
        > >is for a ground wire and not the antenna. Do the 2 wire leads from
        > >the antenna both go to the terminal marked "am
        > >antenna"? What?
        >
        > The radio more than likely uses a ferrite rod antenna/front end
        > inductor. If it has a terminal for the AM receiver it will in all
        likely
        > hood be connected to a wire link wound around the ferrite rod. In
        this
        > case you have 2 choices for coupling to a tuned loop.
        >
        > 1. Simply ignore the connectors and making a physical connection
        between
        > the loop and the radio. Tune the radio to the frequency of your
        choice,
        > then tune the loop to the same frequency and orient the loop and
        radio for
        > best reception.
        >
        > 2. If your loop has a pair of wires coming out (usually from a
        coupling
        > link) then simply connect one wire to the 'AM Antenna' connector
        and the
        > other to the one marked 'ground'. If the wire from the loop is a
        coax type
        > wire, then connect the centre conductor to the 'AM Antenna'
        connector and
        > the shield to the 'Ground' connector.
        >
        > Experiment with both methods.
        >
        >
        >
        > >
        >
        > Jim Dunstan
        > Thunder Bay, ON
      • Jim Dunstan
        ... Okay .... I thought you were using a tuned loop. The loop you describe will be an inferior antenna to your built in ferrite rod antenna. It is designed
        Message 3 of 10 , Aug 9, 2004
          At 10:38 PM 8/9/04 +0000, you wrote:
          OK, I hooked the loop (a cheap, simple little plastic thing that
          comes with an am/fm hifi receiver for the am part) up 1 wire to "am
          antenna" and 1 wire to "ground".  I tuned to a strong local station. 
          When I rotated the loop for strong signal it sounded about like the
          internal ferrite bar.  But, when I rotated to null the station signal
          I got nothing.  Does this indicate that something automatically
          disconnects the internal ferrite bar when I have the loop hooked up?            

          Okay .... I thought you were using a tuned loop.  The loop you describe will be an inferior antenna to your built in ferrite rod antenna.  It is designed for receivers with relatively high gain and no internal antenna (HiFi receiver).  It will work fine for the purpose of picking up strong local signals.  A tuned loop is another thing all together.  They have multi turns and are tuned with a capacitor so they come to resonance.  When the do come to resonance they create a strong electromagnetic field at a very narrow frequency bandwidth.  This field can then be coupled to your receiver by either bringing a receiver with a ferrite rod antenna into its vicinity or if doesn't have a built in antenna you couple using a wire turn or two as a link.  The loop you have would make an excellent link to a tuned loop antenna.  It is in fact exactly what I use for my Hi Fi set.

          My set has the same small plastic loop (8 1/2" dia es 3 turns)  I use it to couple to my tuned loop.  The Hi Fi set works just fine with the plastic loop when receiving local AM stations.  However if I want to pick up stations in say Duluth (about 160 miles away) I bring the plastic loop close to my tuned loop, which I tune to the same frequency.  The difference in reception is like night and day.  The signal increases at least 20 to 30 DB.

          Jim Dunstan
          Thunder Bay, ON

        • realrussian
          Thanks, but what about my question regarding auto disconnect of the internal ferrite bar? When I turn the loop to null a strong, local station (I don t hear
          Message 4 of 10 , Aug 10, 2004
            Thanks, but what about my question regarding "auto disconnect" of the
            internal ferrite bar? When I turn the loop to null a strong, local
            station (I don't hear ANYTHING)doesn't that suggest that the internal
            antenna has been defeated in some way?

            --- In loopantennas@yahoogroups.com, Jim Dunstan <jimdunstan@r...>
            wrote:
            > At 10:38 PM 8/9/04 +0000, you wrote:
            > >OK, I hooked the loop (a cheap, simple little plastic thing that
            > >comes with an am/fm hifi receiver for the am part) up 1 wire to "am
            > >antenna" and 1 wire to "ground". I tuned to a strong local
            station.
            > >When I rotated the loop for strong signal it sounded about like the
            > >internal ferrite bar. But, when I rotated to null the station
            signal
            > >I got nothing. Does this indicate that something automatically
            > >disconnects the internal ferrite bar when I have the loop hooked
            > >up?
            >
            > Okay .... I thought you were using a tuned loop. The loop you
            describe
            > will be an inferior antenna to your built in ferrite rod antenna.
            It is
            > designed for receivers with relatively high gain and no internal
            antenna
            > (HiFi receiver). It will work fine for the purpose of picking up
            strong
            > local signals. A tuned loop is another thing all together. They
            have
            > multi turns and are tuned with a capacitor so they come to
            resonance. When
            > the do come to resonance they create a strong electromagnetic field
            at a
            > very narrow frequency bandwidth. This field can then be coupled to
            your
            > receiver by either bringing a receiver with a ferrite rod antenna
            into its
            > vicinity or if doesn't have a built in antenna you couple using a
            wire turn
            > or two as a link. The loop you have would make an excellent link
            to a
            > tuned loop antenna. It is in fact exactly what I use for my Hi Fi
            set.
            >
            > My set has the same small plastic loop (8 1/2" dia es 3 turns) I
            use it to
            > couple to my tuned loop. The Hi Fi set works just fine with the
            plastic
            > loop when receiving local AM stations. However if I want to pick
            up
            > stations in say Duluth (about 160 miles away) I bring the plastic
            loop
            > close to my tuned loop, which I tune to the same frequency. The
            difference
            > in reception is like night and day. The signal increases at least
            20 to 30 DB.
            >
            >
            > Jim Dunstan
            > Thunder Bay, ON
          • Jim Dunstan
            ... I am sure there is no auto disconnect .... most receivers with the ferrite antenna that have external antenna connections will operate both at the same
            Message 5 of 10 , Aug 10, 2004
              At 07:28 PM 8/10/04 +0000, you wrote:
              Thanks, but what about my question regarding "auto disconnect" of the
              internal ferrite bar?  When I turn the loop to null a strong, local
              station (I don't hear ANYTHING)doesn't that suggest that the internal
              antenna has been defeated in some way?

              I am sure there is no 'auto disconnect' .... most receivers with the ferrite antenna that have external antenna connections will operate both at the same time.  There are a few exceptions .... for example the Sony 7600GR will disconnect the AM antenna when an external antenna jack is plugged in.  The disconnect is mechanical however.  A similar Grundig radio ... the YB400 with the same type antenna jack only disconnects the whip on SW .... but leaves the internal AM antenna. 

              However that does not explain the strange behaviour you are experiencing.

              Jim Dunstan
              Thunder Bay, ON

            • Steve Greenfield
              It probably means the loop is not really tuned to null; instead it is tuned -near- null, and is putting out just enough at 180 out of phase with the internal
              Message 6 of 10 , Aug 10, 2004
                It probably means the loop is not really tuned to null; instead it
                is tuned -near- null, and is putting out just enough at 180 out of
                phase with the internal ferrite to cancel out the signal being
                received by it directly.

                Steve Greenfield

                --- realrussian <realrussian@...> wrote:

                > Thanks, but what about my question regarding "auto disconnect" of
                > the
                > internal ferrite bar? When I turn the loop to null a strong,
                > local
                > station (I don't hear ANYTHING)doesn't that suggest that the
                > internal
                > antenna has been defeated in some way?
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