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10708Re: [loopantennas] (unknown) [1 Attachment]

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  • Craig F. Simmons
    Aug 1, 2014
    • 0 Attachment
      Understand the use of "HDTV" as any part referring that there is something special needed to receive "HDTV" signals is false and inaccurate. The receiving antenna does not care what type of information is being sent, only the frequency. A regular antenna made for analog signals at the same frequency would work just as well. The Fractal loop is just a full wave loop (Adjusted length according to interaction of folding) allowing it to be more compact and smaller. Using  fractal design allows for a "quad" type antenna to have similar gain in a small size. Also it works somewhat different on F/B and forward gain patterns. Magnetic (Fractional loop) is a different thing all together. There are hundreds of articles and books available for reading.


      On Sat, Aug 2, 2014 at 12:04 AM, Myamiphil myamiphil@... [loopantennas] <loopantennas@yahoogroups.com> wrote:
       
      [Attachment(s) from Myamiphil included below]

      I made a fractal antenna for HDTV. Works great.. I picked all the stations in the NY area.
      Essentially a dipole antenna folded down. (UHF) see attachment. I guess if it was resized..... but for lower freqs it would be much larger, using the same design.
       
      Best Regards
      Phil
      WA2069SWL
      Lat: 40.8367633  Long: -74.1768412
       



      From: "Andy ai.egrps@... [loopantennas]" <loopantennas@yahoogroups.com>
      To: loopantennas@yahoogroups.com
      Sent: Friday, August 1, 2014 4:43 PM
      Subject: Re: [loopantennas] (unknown)

       
      Loyd wrote:

         "I heard some one on the air who indicated they were using a Fractional Loop antenna."

      If I heard that, I would seek clarification.

      Until that, I would guess that it might mean either:
      - A Fractal antenna of some kind, or
      - A loop antenna that is a fraction of a wavelength long, also known as a Small Magnetic Loop antenna.

      I've never heard of a Fractal Loop, but I suppose they could exist.  Fractal antennas are somewhat controversial, as to whether or not they actually do anything special, other than just look pretty and perhaps make big bucks for the people who make and sell them.  Fractal antennas are apparently used in cellphones, and that may be their niche application.  I have not heard much about them in significant use elsewhere.  There's a guy named Nathan Cohen who has been a big proponent of fractal antennas, though these days his company (Fractal Antenna Systems Inc.) seems to be more interested in researching meta-materials and 'cloaking' devices, than antennas.  Mr. Cohen has been the target of much ridicule in years gone by.

      Small magnetic loops can be either homebuilt or purchased.  They are the magnetic equivalent of a very short dipole.  They tend to have very large currents and voltages and very narrow bandwidths and require a lot of attention to keep the losses down.  Most small loops are used on the higher HF bands, not 80, but yes they can be used there too.  Losses tend to go up (and bandwidths down) as you go towards the lower frequency HF bands, unless you scale the antenna dimensions up accordingly.  Most homebuilt small transmitting loops require a vacuum capacitor, which is a kind of variable capacitor normally found in high power transmitters.  They can better withstand the large currents and voltages (many 10s of KVs) and keep the I*R losses down.

      The AlexLoop is one of the less expensive commercial small loops.

      Regards,
      Andy





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