What's the story with end-fed antenna's?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KI7QVR, Feb 27, 2018.

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  1. W8IXI

    W8IXI Platinum Subscriber Platinum Subscriber QRZ Page

    If you are fairly new to ham radio and reading this thread for advice you would be better advised to understand that the non-subscriber posters here are just out behind the barn comparing the length of things that don't affect your actual ability to get on the air on HF.

    It's well accepted here and elsewhere that nearly all wire antennas designed and discussed here or anywhere have been around for 80 to 100 years. Wire antenna designs have been well know before most of the posters here were born. Don't delay getting on the air by "paralysis by analysis".

    After following this thread for awhile I pulled out my 1963 and 1969 ARRL Manuals for an antenna refersher. It was refreshing.

    If you are an ARRL member, all of the antenna stuff going back to 1915 is a pretty good read. Clarence Tuska is pretty impressive.

    Some of my original wire creations in the 1960's as a novice would horrify me today. I don't even want to describe them.. As a novice I was only able to get out eight or nine thousand miles.

    Get something in the air and get on the air....

    73, Mike
     
    KC8VWM and N0TZU like this.
  2. W9XMT

    W9XMT Ham Member QRZ Page

    Those considering/analyzing/testing the performance of end-fed antennas should be interested in the comments of Roy Lewallen in his Help file for EZNEC, under the subject End Fed Antennas.

    Below is a clip from those comments in EZNEC v.6.0. The "very short piece of wire" he refers to in the second sentence before the end of the quote applies to the ~0.05λ counterpoise wire suggested for a practical end-fed half-wave (EFHW) antenna.

    That counterpoise wire or a functional substitute for it such as the outer surface of the outer conductor of a coax transmission line connected at/near the end of the single "antenna" wire of an EFHW are required for that antenna system configuration to radiate a significant amount of the Z-matched output power available from the transmitter.

    "Now suppose you have a very, very small battery powered transmitter. Connect one of the transmitter terminals (it doesn't matter which one) to the end of a very high, horizontal wire, and leave the other end open circuited. What happens? You've connected a load (the antenna wire) to one terminal, but there's nothing connected to the other. The source sees an open circuit and no current flows into the antenna wire or anywhere else. ... This is because one terminal of the source is very nearly open circuited since it's effectively connected only to a very short piece of wire. The small amount of current which does flow is due to the mutual coupling between the antenna wire connected to one source terminal and the half segment length wire connected to the other terminal."
     
    Last edited: Mar 15, 2018
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  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    :D I almost spit out my coffee!
     
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  4. AI3V

    AI3V Ham Member QRZ Page

    I agree with the above.

    And too add, it's not that a dipole does not radiate, of course a dipole radiates.

    The trouble with every single "end fed" antenna is we take the absolutely predictable dipole, and make a absolutely random "second half of the antenna"

    And it frustrates me no no end not to be able to give a logical answer when a station asks "my end fed .........." :)



    Rege
     
  5. K9AXN

    K9AXN Premium Subscriber QRZ Page

     
  6. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Brian had some questions regarding end fed antennas. He is trying to sort through the myriad of theories, facts, experiences, and just maybe to actually understand the way the antenna works so he can choose for himself what route to take.

    50 years ago folks knew how antennas worked --- now we know how to use a tool to think for us. Some are still interested in how they work.

    This list just might achieve that objective in spite of ourselves. We've all been out behind the barn --- even the subscribers and have found behind the barn to be a not so good venue. Why? Cuz when we went in for dinner we didn't clean our boots; the results predictable.

    I do agree with your comment to just get something in the air then take the time to understand how it works.

    Have a great day Jim
     
  7. W9XMT

    W9XMT Ham Member QRZ Page

    The best method of predicting/testing the performance of an antenna is based upon using the frequency it is designed to radiate, not on its response to a video pulse with a frequency spectrum many times larger than the antenna is designed for.
     
  8. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    Steve,Is that why you moved from NJ to CA?? :)
     
  9. K9AXN

    K9AXN Premium Subscriber QRZ Page

    The measurement technique is used to extract the surge impedance of the wire that you will use to build an antenna. It is also used to calculate the velocity factor of the wire. You can confirm the velocity factor of your transmission line and use it to sync multi element arrays or simply to confirm the impedance and velocity factor of your coax. It is also used to determine whether the coax you are using is compromised and where on the coax it is damaged.

    Regards Jim
     
  10. W8IXI

    W8IXI Platinum Subscriber Platinum Subscriber QRZ Page

    Brian didn't come back after the first page of what is now a 19 page rambling, confusing, argumentative thread where we found that few were actually interested in Brian at all. His post was just an excuse for what was to happen. On page ten I posted a link to a site which desribed in detail one of the better known and successful implmentations of an end fed antenna- a design I and a lot of other hams have real-world experience with. But it was too late. Brian was obviously long gone by page ten.

    It's unfortunate when a newer ham or a ham new to HF asks a question such as the one Brian asked, and the whole thing veers off into a black hole of comments from older hams from whom I would have expected better. It's about helping another ham, and not about using him in order to get into a contest among yourselves as to who is the "most expert".

    It's still running of course, and it will be interesting to see how many more pages are spent until a "winner" is proclaimed or the contest otherwise ends. I hope Brian is getting some wire in the air.
     
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