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Re: [loopantennas] slinky versus straight wire question

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  • Jim Dunstan
    ... loop type balanced antennas tend to be quieter than dipole type balanced antennas .... and much quieter than antennas end fed against ground. Since you
    Message 1 of 6 , Dec 31, 2009
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      At 01:14 AM 1/1/2010 +0000, you wrote:
      >
      >
      >I have been trying to figure out a way to get some wire up in my
      >crawl-space on the second level of my house .
      >
      >I am only interested in MW at the moment and the lower part of SW , I want
      >the antenna that i make to be very quiet ,I found the plans for the T2FD
      >antennas last night and think it would be very good ariel for me but in
      >order to make one for 500-1700 Khz it looks like it should be on the order
      >of 300 feet long? i don't have that much room. Iv'e read these are very
      >broadband so maybe it would'nt need to be that long .

      loop type balanced antennas tend to be quieter than dipole type balanced
      antennas .... and much quieter than antennas end fed against ground. Since
      you are interested in MW and lower HF reception you will by definition be
      using a "small" loop with very low signal strength to the receiver
      (assuming an untuned loop) with broadband coupling. Putting such an
      antenna some distance from the receiver will require coupling to a feed
      line .... in such a way as to maintain loop and feed line balance .... so
      as to reduce or eliminate common mode currents (a good source of noise). A
      receiver with good sensitivity is required ... or an axillary broadband
      amplifier could be used (best located at the antenna feed point).



      >Then your setup with the slinkys got me thinking? does the extra wire in a
      >slinky (being in a coil)act like a longer antenna ?
      >
      >In other words ,because of the coils in the slinky is there more wire up
      >than just the physical length of the slinky?

      The only thing a length of slinky adds to an antenna X feet long over a
      straight wire X feet long is additional inductance. The added inductance
      could be used strategically in certain antenna configurations to achieve
      resonance .... or to achieve certain phase shifting. In either case the
      resonance or phase shift is frequency dependant .... antithetical to the
      concept of a broadband function.


      >Another question i had ,is there a null with the flag antenna?


      The Flag antenna and other similar type antennas are technically broadband
      loops with the low noise characteristics, desirable in achieving a good S/N
      ratio .... however they are special loops that by virtue of shape,
      resistive terminations, and strategic feed points achieve a directional
      radiation pattern .... usually a cardiod shape. It is possible to cause
      antenna currents within the loop to be maximum in certain portions and
      minimum in others .... causing those portions with current to act in a
      similar fashion to a yagi antenna. To answer your question ... yes, it is
      possible to rotate the whole affair such that minimum reception in the
      pattern can point in different directions.

      Jim
    • david
      have a look here hope this helps cheers david http://www.youtube.com/user/tvdxrools#p/u/147/rgZ4y0Gql6k ... From: Dean Wayman To: loopantennas@yahoogroups.com
      Message 2 of 6 , Jan 1, 2010
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        have a look here hope this helps cheers david http://www.youtube.com/user/tvdxrools#p/u/147/rgZ4y0Gql6k


        ----- Original Message -----
        From: Dean Wayman
        To: loopantennas@yahoogroups.com
        Sent: Friday, January 01, 2010 1:14 AM
        Subject: [loopantennas] slinky versus straight wire question



        I have been trying to figure out a way to get some wire up in my crawl-space on the second level of my house .

        I am only interested in MW at the moment and the lower part of SW , I want the antenna that i make to be very quiet ,I found the plans for the T2FD antennas last night and think it would be very good ariel for me but in order to make one for 500-1700 Khz it looks like it should be on the order of 300 feet long? i don't have that much room. Iv'e read these are very broadband so maybe it would'nt need to be that long .

        Then your setup with the slinkys got me thinking? does the extra wire in a slinky (being in a coil)act like a longer antenna ?

        In other words ,because of the coils in the slinky is there more wire up than just the physical length of the slinky?

        Another question i had ,is there a null with the flag antenna?

        Anyway i would be very interested in how you made your antenna if you would like to post a diagram and specs?

        Thanks

        Dean_0





        [Non-text portions of this message have been removed]
      • Mike
        Hi Dean. I am a great fan of the T2FD, never put one in a loft mind but its an idea I have been thinking of. I am in no way tech in these things so a lot of
        Message 3 of 6 , Jan 2, 2010
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          Hi Dean.
          I am a great fan of the T2FD, never put one in a loft mind but its an idea I have been thinking of.
          I am in no way tech in these things so a lot of suck it and see.

          My garden is 40 ft long and the T2FD just about fitted in I inverted "Ved" it as well, the spacing was 3ft, the tuning was 7-30 MHz I understand a spacing of 5 ft may have got me to 5 MHz must try that this summer, as to using a slinky the extra wire may do the trick over a distance of 40 ft and bigger spacing, bringing the freq down to 3/4 megs who knows.

          It was as I said a great antenna I got to Diego Garsear in the Indian Ocean on 10 watts beating a pile up on 20 Mt's.

          Your need a non terminating 680 ohm resistor hope you can get that OK or make one up from a pile of mixed resistors.

          You can buy ready made T2FD but the price is megger bucks.

          HERES A GOOD TIP, use overhead telephone line wire that the guys no longer want, its steel/copper I think! very strong.

          Hope this helps
          --- In loopantennas@yahoogroups.com, "Dean Wayman" <dean_0_way@...> wrote:
          >
          > I have been trying to figure out a way to get some wire up in my crawl-space on the second level of my house .
          >
          > I am only interested in MW at the moment and the lower part of SW , I want the antenna that i make to be very quiet ,I found the plans for the T2FD antennas last night and think it would be very good ariel for me but in order to make one for 500-1700 Khz it looks like it should be on the order of 300 feet long? i don't have that much room. Iv'e read these are very broadband so maybe it would'nt need to be that long .
          >
          > Then your setup with the slinkys got me thinking? does the extra wire in a slinky (being in a coil)act like a longer antenna ?
          >
          > In other words ,because of the coils in the slinky is there more wire up than just the physical length of the slinky?
          >
          > Another question i had ,is there a null with the flag antenna?
          >
          > Anyway i would be very interested in how you made your antenna if you would like to post a diagram and specs?
          >
          > Thanks
          >
          > Dean_0
          >
        • tenorman1952
          ... Our club has the similar B&W folded loop that we attempted to use on Field Day. It just did not put out. SWR was excellent on all bands tested, but it
          Message 4 of 6 , Jan 2, 2010
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            --- In loopantennas@yahoogroups.com, "Mike" <michaelrae65@...> wrote:
            >
            >
            > Hi Dean.
            > I am a great fan of the T2FD, never put one in a loft mind but its an idea I have been thinking of.
            > I am in no way tech in these things so a lot of suck it and see.

            Our club has the similar B&W folded loop that we attempted to use on Field Day. It just did not put out. SWR was excellent on all bands tested, but it radiated like a dummy load. The club president drove home a few miles away and could not hear it at all.

            In the end, we had only one antenna, mine, a homebrew Buddipole variant, and all contacts made that day were on my antenna.

            The T2FD gets very mixed reviews.

            Paul
            AE5JU
          • Mike
            Something was very wrong with that T2FD mine is ex US war dept type all green, put in a google search, I think the Danish club DXSWG or something like that has
            Message 5 of 6 , Jan 2, 2010
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              Something was very wrong with that T2FD mine is ex US war dept type all green, put in a google search, I think the Danish club DXSWG or something like that has detail, was the T2FD not made by a guy named Countryman in about 1940!!! it was use by the japs during the war as well I understand, so has a long history, so how did my T2FD get a signal to the Indian ocean! if its c&*p. Mike Uk.

              --- In loopantennas@yahoogroups.com, "tenorman1952" <tenorman1952@...> wrote:
              >
              >
              >
              > --- In loopantennas@yahoogroups.com, "Mike" <michaelrae65@> wrote:
              > >
              > >
              > > Hi Dean.
              > > I am a great fan of the T2FD, never put one in a loft mind but its an idea I have been thinking of.
              > > I am in no way tech in these things so a lot of suck it and see.
              >
              > Our club has the similar B&W folded loop that we attempted to use on Field Day. It just did not put out. SWR was excellent on all bands tested, but it radiated like a dummy load. The club president drove home a few miles away and could not hear it at all.
              >
              > In the end, we had only one antenna, mine, a homebrew Buddipole variant, and all contacts made that day were on my antenna.
              >
              > The T2FD gets very mixed reviews.
              >
              > Paul
              > AE5JU
              >
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