Building a ZS6BKW

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N6UM, May 31, 2021.

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  1. N6UM

    N6UM XML Subscriber QRZ Page

    I think I'm just going to do a straight dipole at around 50 feet, higher if i can get it up further. I might just make the wire around 47 feet on each side. and just trim the ladder line until it tunes.
  2. M0AGP

    M0AGP Ham Member QRZ Page

    I am all for experimentation! But I would be a little careful to avoid landing on certain lengths that might give a tuner troubles. For example, 468/10 = 46.8 feet so that will be close to a 30m dipole, which is great for 30m, but that piece of wire used on 15m might show a very high impedance, so might end up being tricky for a tuner to match.
    W5DXP has a very nice spreadsheet that lets you put in your length of wire and your length of ladder line, and you can see which bands will be easy or hard to match. I have a copy of it somewhere but I have a load of edits in mine. The thing is nice and visual and you can immediately play around and see which combinations of wire and ladder line will make your tuner’s life easy or hard.
    If interested we can track it down for you - somebody here will have a link to it.
  3. N6UM

    N6UM XML Subscriber QRZ Page

    The ZS6BKW should be cut to around 47 feet per side anyways. So it should tune right up by just cutting the ladder line. The image belows looks good. Im going to build this antenna over the weekend.

  4. N6UM

    N6UM XML Subscriber QRZ Page

  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    Having done extensive optimizations of a ZS6BKW using AutoEz, the things that effect getting the best match on as many bands as possible depend on wire length, wire shape (flat vs Vee angle), ground conductivity and dielectric constant, height of apex, length of window line, Zo of window line, Vf of window line.

    I would not claim to have a design unless I know ahead of time how high, shape, ground properties, and which specific window line variant (CCS551,552,553,554) is to be used. Knowing those first, I can determine the required wire length and window-line length.
    M0AGP likes this.
  6. W1VT

    W1VT Ham Member QRZ Page

    The free demo version of EZNEC could be used to pre-tune a ZS6BKW antenna. The 20 segments should be enough to model the antenna on the 80, 40, and 20 meter bands.
    M0AGP likes this.
  7. M0AGP

    M0AGP Ham Member QRZ Page

    You’re right! Apologies I misread your post - somehow I read a dipole 47 feet long - my bad.
  8. KK6WBS

    KK6WBS Ham Member QRZ Page

    I have a ZS6BKW in an Inverted V about 35 Ft at the apex. The lowest point in SWR in the 40 Meter Band is around 6.7 Mhz but is only around 1.9. Seeing the same in the 20 meter band (lowest SWR being about 500 Khz below where it should be.)

    I am seeing the same pattern in all the bands (SWR being at its lowest point around 500 or so Khz below where it should be. Also, the lowest SWR reading being around 1.9-2.0 all around (in other words, 1.1-1.5 SWR is no where to be found)

    My question is, Will Trimming the Window Line or trimming and/or folding back the legs, A) Help move me toward 7.0-7.3 Mhz and 14.250 ish ) B) Will trimming the window line vs. dipole legs help with overall lowering of SWR in general? Is any one of them have a greater impact than the other ?

  9. AB6RF

    AB6RF Premium Subscriber QRZ Page

    Based on my experience with the ZS6BKW, I would answer A) Yes, and B) Maybe.

    Like it's been discussed, the ZS6BKW has many variables, and in some configurations (window line Z0, height, ground type, inv-V vs Flat...) it might be difficult to find a good match on multiple bands. But 40M and 20M should be pretty easy.
    I have found that trimming the window line length produces very similar results to trimming the actual antenna wire length, and it can be much easier to do.

    But before you take the trimming too far, check all the possible bands, 80, 40, 20, 17, 12, 10, and 6 Meters.
    My preference is to pay more attention to 10M and 6M and trim for a best match where I want on those bands.
    The higher bands "move" much faster, and the coax losses past the window line are higher, so it makes sense to optimize those bands and then just let the lower bands fall where ever they do.
  10. KK6WBS

    KK6WBS Ham Member QRZ Page

    Thank you for your response. In regards to trimming the window line, would you suggest trimming at the point it goes into the balun or maybe move up the line a bit and take the parts out lets say 7-8 inches above ? For now I assume, I could just use electrical tape until I get the desired result and then solder once I get it tuned ?
    Sorry for the newbie question.

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