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The Pitfalls of Non Resonant antennas.

17 Nov

I have been touching up the “Look and Feel” here a bit. This morning I brightened things up a little by adding a new picture to my header. I also added to my blogroll. These links provide some of the background that helped me get through the last antenna project here at our low profile Ham Radio home. Here are a few of the things I learned while doing this project:

  • While using a no/low gain antennas it is important to manage your received noise floor. Common mode chokes help a lot.
  • RFI to appliances and electronics within my home is managed to zero when proper chokes are employed in the transmitting antenna feed lines.
  • Near field field strength varies as the cube of distance-not the square as I had previously thought.
  • 200 Watts on a balanced feed line and a reactive feed point impedance can easily generate up to 2100 volts.
  • Reactive power causes loss in balanced feed lines.
  • Reactive power destroys baluns, tuners and chokes if not properly sized.
  • Balanced lines most likely are not balanced if they live with other metal objects in the near field-this includes underground objects like pipes, laterals, power lines.
  • For practical purposes, consider near field as anything within a 50 foot radius sphere around your antenna.

These are a few of the lessons learned. I count as a blessing a great deal of hand holding by my Elmer as well as some wonderful web references and tools available in the ARRL Antenna book.

Next steps for me include:

  • Further managing my noise floor by use of a B Field noise antenna to find local sources.
  • Purchase and learn to use the full edition of EZNEC.
  • Improve my balanced feed line chokes by winding better ones using RG-393.
  • Apply X-2 noise capacitors in AC wiring around my home.

Have a great day…

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Posted by on November 17, 2007 in Radio

 

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