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My situation: 66' end fed vs ZS6BKW

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG9LD, Apr 16, 2021.

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  1. KG9LD

    KG9LD XML Subscriber QRZ Page

    Hello all,

    I'm looking for opinions regarding my antenna situation. I'm running an end-fed 66' wire. The feedpoint is at 35' and slopes down to 6'. I'm running 100' of RG-8X across my roof and down into the shack. Not the best situation but I have to make due in my tiny city lot right in the middle of Chicago.
    My SWR is not the best but manageable on the bands. 20 meters, unfortunately, is the worst. I have a Flex 6500 and the ATU is doing a great job.
    I'm wondering about an upgrade of sorts, possibly a ZS6BKW type of dipole which I have room for. I can do this in an inverted V type of setup. The 40' of ladder line would have to lay on top of my roof (again) and then go into 60' of RG-X to my shack.
    Any opinions if this would be a better setup for my situation? Any suggestions and/or opinions are welcome.


  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    The 66ft wire? How fed?

    When you say 20m is the worst, what are you referring to? Swr after tuning? Inability to tune? Noise on receive?

    I would not use the 'BKW if the matching line has to lay on the roof. You are in snow country.
    What is the roof made of?
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The window line laying on the roof isn't good.

    To prevent substantial coupling of that line to the intended radiator it's best for the window line to run perpendicular to the axis of the wires for its entire length.

    But, sounds like a fairly easy experiment to try! Why not try it and see how it works?
  4. KG9LD

    KG9LD XML Subscriber QRZ Page

    Sorry... SWR is high, approx 6:1 on the cw portion of 20 meters. Most other bands are 3:1 or less. My tuner will handle it and I have made a ton of FT-8 contacts recently on 20 meters but it's not ideal. I'm feeding it with 100' of RG-8X run across my roof and into the shack.
    I am in snow country. The roof is just asphalt shingles over a wood frame.
  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    Please describe how you are feeding the 66ft wire?
  6. KG9LD

    KG9LD XML Subscriber QRZ Page

  7. KI8DJ

    KI8DJ Ham Member QRZ Page

    That antenna has a 9 to 1 unun. I have similar one. Looks like you have a half wavelength of wire which is resonant on 40/20. You want a non resonant length with that transformer ratio. balun designs has a chart of off lengths to use. You can either shorten or add.
    I found a length where I can tune 160 through 6 with a 3 to 1 tuner.
  8. WA2COP

    WA2COP Premium Subscriber QRZ Page

    Your issue is your running a resonant antenna with an improper transformer. The feed point at 66 foot is 3000 ohms. Your 4 to 1 will not match the impedance. If your going to run 66 foot which is a resonant length, you need to be running a 49:1 transformer (with a capacitor terminated) to achieve a <2:1 on the non-warc bands. A 4:1 is more of a random length antenna and must NOT be at resonant lengths. So, shorten it or lengthen it like KI8DJ mentioned.

    But to add to that - the moment you go to anything less than a 1/2 wave, you will need a counterpoise.

    Personally - I would just change out the transformer and since your OK with the 66 foot length you will get 10 - 40 NON-WARC bands <2:1 and on the WARC bands you will be <4:1 (or better) - your tuner can easily handle it. Lastly, you wont need a counterpoise/radial.
    Last edited: Apr 16, 2021
    KU3X and WA7ARK like this.
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    You should convert your antenna to a configuration similar to this:

    or this:

    The commercial versions also have what I call a "compensation coil", which aligns the higher order harmonics such that no tuner is needed on four bands.

    I discuss methods of harmonic alignment for EF antennas in the slide show linked to at the bottom of my QRZ page.

    If you are up to building the antenna from parts, I can help you with the required wire lengths, coil inductance, and coil placement.

    If you are receiving a high noise level, choking/grounding the coax run between the antenna and where it enters your ham shack will likely reduce the resting noise level in your receiver. Write back if you would like to try this. First fix the antenna, then tackle the noise reduction as a second step...
    Last edited: Apr 16, 2021
    K1LH likes this.
  10. KO4CQ

    KO4CQ Ham Member QRZ Page

    I recently installed a ZS6BKW. Although it is not at full height yet, and 8' at one end is hanging straight down, I am pleased with the results. My interest is mainly 40 and 20. The SWR on 40 is nearly flat across the band, and on 20 it is 1.5:1 (about) in the middle of the phone band. I don't even need to use the internal tuner in my TS820S (I usually do, though). It's simple, cheap, and cut to the correct dimensions, does not need tuning. Here's a link to more than you would probably ever want to know about this antenna. I don't know how the ladder line (a matching section) would work laying on the roof.
    K1LH likes this.

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