Re: Antenna

Kelly Jack
 

Summary of Steve Ellington's video presentation on efhw on youtube.

  • First half up to minute 38 is a bit of a history on how the efhw arose, starts with the zepp. Talks about longwires fed by 9:1 unun. EFHW stuff starts at 38 min and you could probably skip to here and not miss much. Quite easy to watch at 2 times speed.
  • Steve mentions that he is not an EE or considers himself to be an antenna expert rather someone who has been experimenting with antennas for a long time.
  • Steve dissects a myantennas efhw 8010. See attached snippet from the video.
  • Grounding methods are discussed. Recommendation is to ground at the transformer and again at the radio end for max measured current. Note he uses a version for 20m for this test. See snippet pic for his summary.
  • Uses same 20m version to compare with a dipole version and compares radiated rf. Note that this is not far field.  Steve finds EFHW equal to the dipole version in this test.
  • Beyond just an EFHW Steve shows how to add 160M (and 60M and 6M).  Requires an extensive ground system which sort of defeats one of the attractions of the EFHW.  See pic. The schematic drawing in the video does not have a cap that was needed so I have added it.  Blue lines represent the cap which Steve says needs to be 0.0015pf (this does not seem right to me). Note this cap and schematic is only required for the extra bands.  Potentially 60M and 60M could be reached with a tuner??  I don't know.
  • 75M option.  As constructed the antenna resonated in the lower end of he 80M band. Add a cap (250pf - 500pf) at the half way point to resonate at 75M without impacting the other bands.
  • Compensating coil. The antenna resonates most bands at the upper end of the bands, ie phone end.  if you want the CW end of the bands add a coil, 5 turns of 14ga enamel copper wire on 1 inch coil 72 inches from the transformer.  See snippet (from another video).
I do recommend watching the video and others on Steve's channel, I find Steve to have a personable style, a more scientific method than most when it comes to antennas and he has other radio videos that I have found useful.  IC7300 seems to be a theme also. And there is a video on an interesting monoband antenna called a folded counterpoise which is a 160M antenna that uses a full length counterpoise folded back on itself a couple of times underneath an inverted L wire instead of a ground screen. Not really what people are after in this thread but interesting nonetheless.  I have no association with Steve or his channel.

Regards




Simon
VK3ELH

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