80M off-center-fed dipole - best feed point? - feedline type? - compared with center fed?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K1HL, Dec 9, 2019.

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  1. K1HL

    K1HL Ham Member QRZ Page

    Thank you all for your insight. Ideally, of course, I would run the dipole diagonally across the property, thereby putting the wire through my bedroom. The suggestion that I use a vertical would be excellent, as W1VT observed. And, yes, I am directly on the beach, but I don't own the beach. The best I could do would be two short radials within my lot only. I believe that an inverted L with only a forty foot vertical portion and a poor ground wouldn't work well either.

    So the question narrows to this:
    1) A shortened (96ft) ZS6BKW center fed with ladder line (or coax?), dipole - no bend needed!
    2) A full length 135' dipole off center fed with ladder line, with a single 90 degree bend in one leg at about 40 ft from the end.
    3) A "real" Windom antenna 135 ft long, with single wire feed of any length connecting to the dipole at the 45 foot point from one of the ends. Would also require the 90 degree bend 40 ft from the end.

    WA7ARK, thanks for the precise calculations. You are correct - lots of wasted energy going to the moon. You must be an engimaneer...

    Thanx everyone.
    K1HL, Harry
     
  2. W1VT

    W1VT Ham Member QRZ Page

    I think you would be surprised what you could work with a highly compromised Inverted L, as it is the interaction with the water off in the distance that will really help your signal.

    I made 500 contacts in the 160M contest this weekend with a 36' high Inverted L that fits in by 70x100 ft back yard! You may not be a big signal on 80, but I suspect that you will be strong enough for the DX to hear you on CW and FT8. I get really well on 80M with a 40' high vertical--I have 227 countries confirmed. 134 on 160. My radial system is four elevated radials across the back yard. For both bands.

    DX-peditions with locations like yours next to the beach get out really well using verticals.

    http://www.k2kw.com/6y2astory/story.html

    Zak W1VT
     
    Last edited: Dec 9, 2019
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  3. K8JD

    K8JD Ham Member QRZ Page

    WHY OCF
    The whole idea of the OCF antenna is the higher then 50 Ohm and lower than 2KOhm feedpoint ,
    This higher Z and using higher Z feedline (450-600 ZOhm line) lets you get away with high SWR and reasonable transmission line losses when you work on other than resonant freqs !@
    I like having several halfweave dipoles fed with coax, I use one band per antenna . One antenna per band. never have to mess with a tuner.
    For the DX bands using a vertical works fine and your inverted L is really a vertical !
     
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  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    I'm with W1VT on this one. You may be pleasantly surprised with an inverted-L even with only a pair of radials.

    If you really can get 40 feet of vertical before the L top that's actually very good. A full sized 1/4 wave vertical on 80m is only 65 feet tall so 40 feet is really quite good. If there's any way to elevate those ground radials, even a couple of feet they could be very effective but even with only a couple of ground radials and perhaps some ground screening in near the feed point (or a bunch of very short radials near the feed point) you will likely do much better with an inverted-L or other vertical than any low horizontal antenna with your QTH right up against salt water.
     
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  5. WD4ELG

    WD4ELG Ham Member QRZ Page

    I vote for the inverted L also. I am lucky that I have very tall trees, I have a 1/4 wave 160 vertical that I can use on the other bands and it does work surprisingly well...the vertical portion is 95 feet long.
     
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  6. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    I don't understand either.
    20 bucks and 60 minutes .... you could be on the air with a dipole that would work as well as anything you chose except maybe the ZS6BKW.
    Just because a simple dipole is old and common, doesn't mean it's not effective.

    The dipole I mentioned was one of Cebiks favorites according to his writings ........
     
  7. K1HL

    K1HL Ham Member QRZ Page

    Hi Zak, Appreciate your comments. A question about your radials: How high, how long, and are they evenly spaced. What if, with 2 radials only, I wrapped one radial halfway around the perimeter of my house, with the other doing the same, but in the opposite direction? Radials are a real problem here... would four or more deep ground rods going to salt water work? Any other ideas on compromise radials?
    Harry K1HL
     
  8. W1VT

    W1VT Ham Member QRZ Page

    I'd suggest symmetric radials of equal length. This should force and equal amount of current into each radial. I suppose you could measure the current into each radial and adjust for symmetry.

    Ground rods are a poor substitute, an Inverted L results in a better compromise antenna than a vertical if you just have ground rods.
     
  9. K1LKP

    K1LKP Premium Subscriber QRZ Page

  10. WA7ARK

    WA7ARK Ham Member QRZ Page

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