1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice

Homemade Dipole, High SWR?

Discussion in 'CB Antennas' started by office888, Sep 6, 2009.

  1. office888

    office888 Active Member

    Joined:
    Jun 8, 2009
    Messages:
    499
    Likes Received:
    11
    Decided to try to make my own 11m dipole.

    Used an SO239 "Tee", and 2 x 239 fittings. I split 16ga lamp wire down the middle. Each leg is 103.25". I soldered one side to the center signal fitting, and the other to the outer ground fitting.

    So then I went to check the SWR before I hung it up. I laid it out, and checked it with TWO different meters. SWR overall is high, almost 10:1.

    Any ideas? Do I need a Balun?

    -Richard-


     

  2. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

    Joined:
    Oct 23, 2005
    Messages:
    5,964
    Likes Received:
    941
    check for a short
     
  3. Jay in the Mojave

    Jay in the Mojave Active Member

    Joined:
    Apr 6, 2005
    Messages:
    309
    Likes Received:
    6
    Hello Office 888:

    You first sentance is hard to follow. What are 2 x 239 fittings???

    The SWR will be high just laying on the ground. This is not a good SWR test.

    Its a know fact that dipole antennas as most all antennas will change SWR when the heigth is changed.

    The SWR will change with heigth, but if your not using a Balun the SWR can get crazy and not work to well. Some dipole antennas without a Blaun will seem to work, but all my experiences show the use of Current Balun is a good call.

    The ARRL Antenna Book and Radio Handbook show how 1 to 1 Current Baluns are used and made.

    Best 1:1 Balun 1.5 - 54MHz Dipoles & Yagis 5kw - #1115
    Transmitting Baluns
    BALUN UNUN

    The higher the dipole antenna the better.

    Good Luck

    Jay in the Mojave

    Upate: Here is a great paper on the Balun, and its uses.

    http://w2du.com/r2ch21.pdf

    The Book Reflections II is well worth the Doe Ray Me.

    Jay in the Mojave



     
    #3 Jay in the Mojave, Sep 6, 2009
    Last edited: Sep 20, 2009
  4. HiDef

    HiDef Active Member

    Joined:
    Aug 16, 2008
    Messages:
    543
    Likes Received:
    6
    The antenna needs to be checked in it's operating position or the test isn't valid. Drooping the ends into an inverted V might be necessary for a 1:1 match.

    Plan to put it up and take it back down a few times. This is the price we pay for the simplicity of a coax fed resonant sky hook.

    Make a coax coil BalUn from the existing feedline. No need to buy anything. All you need are a few turns at this freq. Plenty of info on the web about that.
     
  5. Beetle

    Beetle Sr. Member

    Joined:
    Dec 7, 2005
    Messages:
    2,925
    Likes Received:
    809
    What Marconi said. Use a multimeter and check at the radio end of the coax. You should see infinite resistance between the center and shield. If you see any measurable resistance, you have a problem either with the connections you made, or with the coax itself.

    Get some regular wire antenna insulators. UHF connectors aren't designed to be insulators by themselves, and they're expensive. Insulators are cheap.
     
  6. Quiksilver

    Quiksilver Active Member

    Joined:
    Oct 23, 2006
    Messages:
    385
    Likes Received:
    18
    Do you have pics of your connections? Sounds like a short as previously mentioned. Should look similar to these:

    [​IMG]

    [​IMG]
    Or if you used the SO-239 tee, it should look like this.
    [​IMG]
     
  7. freecell

    freecell BANNED

    Joined:
    Apr 6, 2005
    Messages:
    1,430
    Likes Received:
    13
    the radiation resistance required for a reasonable match is non-existent as long as it's laying on the ground.
    Dipoles, Radiation Resistance
     
    #7 freecell, Sep 6, 2009
    Last edited: Sep 6, 2009
    mackmobile43 likes this.
  8. mackmobile43

    mackmobile43 Jock Supporter

    Joined:
    Feb 11, 2008
    Messages:
    6,709
    Likes Received:
    381
  9. Beetle

    Beetle Sr. Member

    Joined:
    Dec 7, 2005
    Messages:
    2,925
    Likes Received:
    809
    Quiksilver - I would DEFINITELY put some insulating sleeving or at least some tape on the lead going to the center of the SO-239. Hanging that up as it is is an open invitation to the wind gods to blow the whole thing around until you have a complete short at the feed point.

    Also, if you're happy with the performance of the antenna, I'd suggest you solder the places where the wire is wrapped around itself. It has a tendency to stretch a bit anyway, and soldering things will keep the resonant frequency from getting significantly lower than it is, at least for a while. Just enough soldering to keep things from pulling apart.
     
  10. Quiksilver

    Quiksilver Active Member

    Joined:
    Oct 23, 2006
    Messages:
    385
    Likes Received:
    18
    Yeah,
    That was just a temp setup that's long since taken down. Definitely would have done what you suggested if it was up longer.
    Thanks!
     
  11. packrat

    packrat Active Member

    Joined:
    Sep 24, 2008
    Messages:
    749
    Likes Received:
    16
    I never bother using an so-239, or any connectors at the antenna, I just wrap the coax on the center insulator and solder the legs to the elements where they are connected to the insulator. Strong, Cheap, Easy and lots less to go wrong!!!

    FWIW


    PR
     
  12. W5LZ

    W5LZ Crotchety Old Bastard

    Joined:
    Apr 8, 2005
    Messages:
    6,832
    Likes Received:
    775
    Just out of curiosity, what problems have you had with SO-239 or PL-259 connectors?
    - 'Doc
     
  13. packrat

    packrat Active Member

    Joined:
    Sep 24, 2008
    Messages:
    749
    Likes Received:
    16
    OH, lets see... connectors that come loose in the wind, water intrusion since they are not weather proof, corrosion from exposure...

    PR
     
  14. Jay in the Mojave

    Jay in the Mojave Active Member

    Joined:
    Apr 6, 2005
    Messages:
    309
    Likes Received:
    6
    Upate: Here is a great paper on the Balun, and its uses.

    http://w2du.com/r2ch21.pdf

    The Book Reflections II is well worth the Doe Ray Me.

    Jay in the Mojave
     

: dipole

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!