End Fed Half Square

A 20 meter end fed half square antenna should probably have the following properties:

• Easy to errect:
  • Two 20 foot fishing poles staked in the ground 34 feet appart.
  • Feed a starting from the 3 foot level up one pole to the top which will bend down a bit... maybe a foot, then over to the top of the other pole and down to the three foot level again.
  • Attach a high impediance antenna tuner (parallel tuned tank) at the three foot level.
  • Stay away from ends during operation... stray capacitance will detune the antenna and besides that, you could get rf burns if you touch the end while transmitting.
• 20 meter operation:
  • High impedience end feed so an extensive ground not needed
  • coax feed not needed so none to carry.
  • Low angle of radiation
  • NEC model
    • nec file
    • 
• 40 meter operation:
  • High impediance end feed so an extensive ground is not needed.
  • High angle of radiation - NVIS antenna
    • The high current portion is in the middle of the horizontal top making it look very much like a low dipole. The high impediance ends provide some loading but radiate very little.
    • nec file
    • 
    • When grounded at the far end, the antenna performs like two phased verticals. A comparison of the high impedance end versus the terminated end shows that leaving the far end open is useful for NVIS and grounding it is good for low angle radiation. In practice, I didn't notice much difference when listening to signals which should have been arriving at a low angle.
      • 
• 80 meter operation
  • Low impediance end feed - it's a quarter wavelength.
  • High angle of radiation
    • It may be a combination of low angle of radiation because the low impediance forth is vertical and the middle two fourths are horizontal. The high impediance probably doesn't have much affect.
  • extensive ground needed... how about unrolling a roll of tin foil under it.
    • nec file
    • 

12 October 2004 test

• Built with 2 20 foot fishing poles. Top corners probably 18 feet high.
• Resonated at 3.46 MHz.
  • With aluminum foil ground directly under element - 42 ohms
  • With +/- 16 feet of aluminum foil at right angles to driven base 34 ohms.
  • With aluminum foil ground directly under element and +/- 16 feet of aluminum foil at right angles to driven element, 25 ohms.
  • Disconnect +/- 16 feet of aluminum foil but leave on ground & use foil under driven element yields 50 ohms.
• Grounded far side of loop to give low impedance feed point on 40 meters and to attempt some directivity and low angle of radiation, but there was very little difference between that and the dipole on the fence (5 feet up)... maybe an S unit but maybe only detectable on foreign broadcast stations.
• Compared to loop in attic:
  • ke7bk could not hear my 4 watts on 40 meters on the dipole or half-square dipole but he could hear the same rig when connected to attic loop.
  • ke7bk could hear my 4 watts on 80 meters... Maybe an S5-7.
  • ke7bk could barely hear me on 160 meters and the antenna tuners would not load to give an acceptable SWR.
• Had QSOs with Arizona and Pennsilvania while running 4 watts into the high impedance end fed configuration.