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EFHW vs Random wire

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W6TC, May 29, 2020.

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  1. W6TC

    W6TC Ham Member QRZ Page

    I have space/height limitations at home.
    I have the option to put up an EFHW or a longer end fed long wire, maybe about 80 feet.
    Height at the highest point would only be about 20 feet.
    Which one have a performance advantage over the other on say 10,15,20 and 40?
    According to this https://udel.edu/~mm/ham/randomWire/ an optimum length for my space restrictions could be 70 feet which would give me 80-40-30-20-17-15-12-10 as opposed to the EFHW which is advertised as resonant on 40/20/15/10m.

    Thanks
     
  2. WA9UAA

    WA9UAA Ham Member QRZ Page

  3. KK4OBI

    KK4OBI Ham Member QRZ Page

    The usual problem for hams is getting height. Low antennas radiate the ground under them and the rest of the RF reflects skyward until the wire is up around a half-wave above ground. At that height the directional, high-gain figure eight pattern they show us in books develops. Half-wave height is 16 feet at 10 meters, 32 feet at 20 meters, 64 feet... you get the idea.

    A vertical antenna radiates in all directions, except up, from ground level and higher. That is one of the reasons hams use verticals when they can't get height. Another benefit is the SWR is hardly effected if you tune it low then raise it high.

    A dipole mounted vertically is still a dipole and needs no radials. The length of the end near ground needs tuning. Angling the low end of a dipole is the way to get best SWR.
    Look up Bazooka antenna. Commercially look at Gap Antennas.

    A vertical monopole or inverted -L fed at or near ground level needs many untuned radials on the ground. An elevated vertical monopole needs at least two tuned elevated radials per band. Three of four radials per band are slightly better. Look into Remote Auto-tuners for multi-band operation

    Commercial multi-band vertical$ have decoupling radials for different bands but work best with ground radials. Look at Cushcraft R8 and Hy-gain HGN-AV.

    Having both a long wire and a vertical gives you the freedom to pick which is best at any moment.
     
    M0AGP, N6KX, WA8FOZ and 4 others like this.
  4. KC3GHK

    KC3GHK XML Subscriber QRZ Page

    Like said with out height a lot of energy will go straight up, however if that is all you can do then try it and get on the air. Any antenna is better than NONE. I use the end fed wire lengths recommended by Balun Designs on their web site and run them as Inverted L's feeding them at ground level at the corner of my deck as Marconi's (verticals) AND use a 1 to 9 UnUn. I have done well with 53 feet, 72 feet, 98 feet and currently 124.5 feet and a 9 to 1 UnUn with lots of radials on the ground lug. If you want to avoid radials you will need a Half Wave End Fed and use the coax feed line as a counterpoise which will mean using a 1 to 1 current choke down the coax line before entering the house. You also need to be aware and take care of electrical grounding before entering the house and follow NEC (National Electrical Code) grounding rules tying any ground rods mechanically with number 6 wire or better to the electric service ground rod. Read up on proper grounding. You could get a fiberglass push up pole to run your wire up and then out if using a 9 to 1 or 4 to 1 UnUn and recommended wire length (it's NOT random) along with some radials or if a half wave end fed use the pole to hold the transformer off the ground and above houses and buildings. Good luck. Just get started and play with wire until you get something that works best for your location and situation. Google ideas on line and get some antenna books for ideas. Lots of fun experimenting.
     
    W6TC and K0UO like this.
  5. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Just get something up and try it

    remember: "The Best antenna is one that's, In the AIR and ON the AIR"
     
    NX6ED and KU3X like this.
  6. W6TC

    W6TC Ham Member QRZ Page

    I already have up a fan inverted V for 20/40 feeding an Elecraft K1. It works ok.
    I am looking at getting a multi band rig and want to make sure I have a mutiband antenna to match.

    Thanks for the replies.
     
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    If you are constrained to a "low" antenna, then a not-resonant-on-any-desired ham-band inverted-L wire fed against a modest set of on/in earth radials through a 50:450 auto-transformer (aka unun) placed just above the radials, with low-loss coax (to minimize coax loss) is about the best you can do... This set-up requires an in-shack wide-range coax tuner. Likely if your rig has a built-in automatic tuner, that will not have enough matching range.

    If the vertical part of the inverted-L is say 20ft tall, and the horizontal part of the inverted-L is 53ft long, then that makes usable (not great) antenna for 80m to 10m. This is based on the RG8X coax being 55ft long (makes a difference), and 4ea 20ft radials under the vertical section...

    The performance on 80m is the worst compared to the other bands, but it should enable you to make some contacts there...
     
    Last edited: May 29, 2020
    AJ6LB and KC3GHK like this.
  8. W4KJG

    W4KJG Subscriber QRZ Page

    For a very interesting read, there is a great article about Yardley Beers, w3AWH/W0JF, who assisted W3EDP's antenna experiments. Mr. Beers then wrote an article about it for QST in 1936. I don't believe I ever worked Mr. Beers, but for those of us who were licensed from the 1950s to the early 1990s probably know a little bit about this extremely interesting person. He was still active into the 1990s at age 91. His wife wrote a great article in 2004 for QST about his and her life. It can be downloaded here: https://www.qsl.net/w0dk/scholarship_files/yardley.pdf

    Enjoy.
     
    W6JJZ likes this.
  9. W6TC

    W6TC Ham Member QRZ Page

    2E0CIT likes this.
  10. AC6LA

    AC6LA Ham Member QRZ Page

    Wow, thanks for that link. Reminds me that us young squirts (I was first licensed in the late 60s), with all of our Computer-This and Internet-That, still can't hold a candle to some of the old timers.

    Dan, AC6LA
     
    M0AGP likes this.

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