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Sky High SWR

Discussion in 'Amateur Radio Antennas' started by Keith Thompson, May 12, 2018.

  1. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    I put up a 73' dipole antenna between two trees and hooked it up this week. The antenna is above the house and about 20' away. I let the ladder line droop until it was even with the eaves, then ran it along the eave to the balun. From there, I ran the heavy 400 coax down to a surge arrestor attached to a copper grounding bar, then another coax back up to a pass-through in my second floor window, then another length of coax to the Icom IC-7300. This was the wiring plan suggested by someone at Ham Radio Outlet to address my grounding concerns operating from a second floor.



    It will probably come as no surprise that the SWR is pegged and the built-in tuner in the 7300 just beeps once and gives up. I tried running the coax from the balun directly to the radio, but the results are the same. I don't know if I'm misinterpreting the radio's SWR meter or if I really have a problem here. Don't want to burn out the transmitter.

    Desperate for help. Anyone want to tackle this?
    IMG_5112.jpg IMG_5115.jpg
     
    #1 Keith Thompson, May 12, 2018
    Last edited: May 12, 2018

  2. Robb

    Robb Yup

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    I'll bite . . .

    The ladder line is coiled up?!?
     
  3. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    Only the last six feet or so. The total length of the ladder line is 82 feet, I believe.
     
  4. Beetle

    Beetle Sr. Member

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    Is this a center fed dipole, or off-center FED (OCF)?
    Are your rain gutters metallic or plastic? Same question for siding.
    Ladder line should never be coiled. Coax is different; it CAN be coiled- carefully.
     
    Captain Kilowatt and Robb like this.
  5. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    IMG_5117.jpg IMG_5118.jpg IMG_5119.jpg IMG_5117.jpg IMG_5118.jpg IMG_5119.jpg
    Center-fed, no rain gutters, cedar siding. The manufacturer of the antenna says that excess ladder line can be loosely coiled. This coil is a little tight, but not sure it's enough to cause SWR this high. Could be wrong, of course.
     
    #5 Keith Thompson, May 12, 2018
    Last edited: May 12, 2018
  6. Beetle

    Beetle Sr. Member

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    There are a lot of connectors involved, so first, I'd disconnect the coax at the balun and see if there's a DC short circuit between center conductor and shield - somewhere. If there is, you'll have to disconnect bit by bit until you find the short.

    But if the coax checks out okay, I'd shorten the ladderline enough to eliminate any coiling.

    If you have access to an antenna analyzer it could be a big help in measuring just what the antenna conditions are.

    And what kind of balun are you using?
     
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  7. n8fgb

    n8fgb Well-Known Member

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    Keith Thompson likes this.
  8. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Looks like ALM sofit material....I'm with Beetle...regardless of what the Mfgr said Ladder Line should NEVER be coiled.
    And 73 ft dipole? What bands did they say this was good for? To short for 80/75m and to long for 40m?
    4:1 Balun?
    Give us some more info please.
    All the Best
    Gary
     
    Robb likes this.
  9. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    Brand new 4:1. Coax is all new, as well.
     
  10. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    The manufacturer claims it's good for 80 to 10 meters. It's a Granite State Ultralite Junior. 4:1 balun. I've been told not to cut the ladder line, that it's okay to coil the excess in loose coils, not to coil it. It's a little confusing. Ideally, I'd cut the excess six or seven feet off and call it good, but I'm too new at this to gauge what effect it will have on the antenna. I actually talked to France on 40 meters the other night with a good signal, but I've stopped transmitting until I resolve this issue.

    What would you do with the excess? I don't have room to move the antenna.
     
  11. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    Thanks, I was considering one of these. May take a chance on one.
     
  12. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    OK Keith: Couple things: First the Ladder line on that antenna is part of the antenna, and really a matching stub. That needs to be fully extended. So uncoil the excess let it droop down past the eve and then bring it back to the balun.
    As you can see below is a quote directly off HRO website: BALANCED ANTENNA TUNER required.
    I am sorry I totally disagree with the Mfgr., that using a 4:1 current Balun and the radio's internal tuner with a random length coax to connect with, will make this antenna work 80-10m as stated. My 2 cents!
    The correct way I would suggest, has been stated already A BALANCED External Manual tuner with Ladder Line connected directly.
    Sorry but the Mfgr. is in business to SELL antennas, and I disagree with much he states on his website in regards to this working effectively and 80-10m using a radio's internal tuner.
    However you may get it to do so by bringing the coax from the Balun directly to radio...shortest possible length.
    Then ground the Balun and radio to your nicely done ground buss via like a #6 piece of std building wire. Try it that way.
    To get better quickly try uncoiling the Ladder line...Do not cut it off and let it loop as straight down as possible from the feed point. Then bring it to the Balun as you have done.
    See if this improves the performance.
    My suggestion is to look to purchase a BALANCED ATU...ie...
    https://www.mfjenterprises.com/Product.php?productid=MFJ-974HB
    http://www.palstar.com/en/bt1500a/
    Old JOHNSON MATCHBOX...(google Link Coupled Tuner) designed specifically for Twinlead feed antennas.
    However any antenna tuner with a BUILT-IN 4:1 balun should work well...These above will be more efficient.
    Or build one...really not tough. I use a HB Double "L" style much like the Palstar

    Great info here:
    http://www.somis.org/bbat.html
    http://ka4cid.blogspot.com/2008/12/w4mmq-legacy-balanced-antenna-tuner.html
    https://twit.tv/shows/ham-nation/episodes/262

    My antenna is essentially a homebrew "LAZY H"(google that+W8JK antenna) laying Horizontal feed directly via the 300 Ohm KW+ rated Twinlead and tuned with either my HB Double "L" or my PALSTAR AT4K tuner.
    Does pretty damn nice job 80m -15m for an antenna only about 40ft above ground.
    Ok enough for now...Enjoy the experimentation...that's some of the great fun of Amateur radio...messing with antennas!
    All the Best
    Gary/W9FNB

    GRANITE STATE Cobra-Ultralite-JR
    3.5 - 30 MHz 73 Foot Dipole with Ladder Line - Requires Balanced Antenna Tuner
     
  13. Keith Thompson

    Keith Thompson AC1EG, Guns & Radios, Icom IC-7300, Yaesu FT-60R

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    Gary,

    Thanks for the terrific information. I appreciate your taking the time.

    Earlier tonight I ordered an MFJ -993B Antenna Tuner, Intellituner, Automatic, Desktop, 300 Watts, 160-10 meters. Should be here Wednesday. I ordered it before reading your missive. Will the 993B work or do I need the one you suggested that is designated "balanced"? If the 993B won't work, I'll cancel and reorder the 974HB.

    In the meantime, I will uncoil the ladder line and, as you suggest, drop it down and then bring it back up to the balun and see what that does when the tuner arrives.

    That's going to be an awfully long ground wire from the balun to the ground bar, but I guess it's better than no ground at all.

    Keith

    _____________

     
    #13 Keith Thompson, May 13, 2018
    Last edited: May 13, 2018
  14. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Kieth: That tuner should work. Be sure to bring the ladder line directly to it for best operation. (NO COILS) Loose the coax and balun.
    MHO... I don't like auto tuners...there are those that swear by them...However I just don't like some pile of computer chips and some embedded software telling me my antenna is correctly tuned.
    OLD school me! I like doing the tuning because I have done it for almost 40 years. I know how it should tune, and what to expect. Again MHO
    Hope to hear you on the air soon. Don't forget to put up a 6m dipole...Fun band...that tuner will not work with your antenna for 6m...but small, maybe not even significant issue for you...
    All the Best
    Gary
     
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  15. DainBramage

    DainBramage Well-Known Member

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    ....[​IMG]
     

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