High SWR ON EF QUAD

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  • #1005
    kiheiman
    Participant

    I just put up an EF Quad antenna – up 30 feet on one end on a fiberglass pole. The antenna slopes down to the peak of the roof on the end with the matchbox. The antenna is very low in resonance on the 40M, 20M, and 15M bands – about 5.8 MHz on 40m. We folded back the far end about 6 feet. That helped some, but the SWR is still about 5:1 at 7.160 MHz. Any ideas on what might be wrong? There is a heat pump about 8 feet away from the antenna section with the tuning stubs.

    73
    Clint
    W7KEC

    #1006
    QRPME
    Participant

    Clint,
    #1> Is the heat pump directly under the radiator or off to the side?

    #2> Instead of just folding the excess back, be sure it is wrapped tightly on itself for two or three close turns (like a hangmans noose), then let the remainder hang free instead of wrapping it back on the radiator.

    #3> Can you give me SWR readings at:
    7.000 =
    7.100 =
    7.200 =

    #4> What are you using to measure SWR?:
    antenna analyzer,directional watt meter, rigs internal meter etc.

    The more information the more we can help.

    73 for now,
    Randy_KB4QQJ

    #1011
    QRPME
    Participant

    Clint,

    You can trim/tune the antenna in one of two ways: Either cut the wire or wrap the wire back along itself toward the feed point. I prefer cutting the wire for the very bottom of the band, (cw portion) then wrapping to shorten it to the voice portion.
    Be sure the wire is routed through the insulating anchor before wrapping, and you may wish to use a combination of cutting and wrapping to carefully trim into just the right frequency without having an excessive wire wrap. In wrapping, be sure the wrap is as tight as you can get it in small loops back around the main radiator. Make it look like a small hangmans noose.
    Photo- http://www.kb4qqj.com/wrap.jpg
    If you are now getting the lowest SWR at 5.8 mHz you will be reducing the antenna length roughly 39″ to get to the low end of band.

    #1013
    kiheiman
    Participant

    The heat pump is off to the side of the antenna wire. We used the following ways to check SWR – Youkits Antenna Analyzer, MFJ-259, Diamond SX-600 SWR Meter, and SWR meter on Kenwood TS-2000 transceiver. We did not tie back the folded over wire as you recommended – just a few turns around the main wire so that the folded back wire runs in parallel with the main wire and a turn about every six inches.
    We moved the antenna so that is was about 25′ away from the heat pump – SWR readings are still bad. We put a 50 ohm dummy load on the end of the coax and the SWR was 1:1 over all the bands. Will need to get you the SWR readings that you requested.

    73
    Clint

    #1014
    kiheiman
    Participant

    Here are the SWR readings:

    7.000 = 6.8
    7.100 = 7.0
    7.200 = 7.3

    73
    Clint

    #1015
    QRPME
    Participant

    Clint,
    I spoke with Larry and it seems a number of antennas shipped with a radiator 10-12 feet too long. Either measure your radiator to 65 feet and start from there or fold back about 10 feet and see how that affects the swr. If it draws it much closer to spec, then start trimming it in 4 foot increments to sneak up on the correct length. Let me know how it works out. We apologize for the confusion.

    Randy_KB4QQJ

    #1021
    kiheiman
    Participant

    We took the EF Quad to the park and set it up out in the open with no surrounding objects. 30 foot pole on one and and 7 foot pole on the other end. Checked the SWR and the resonant point was still 5.8 MHz. We laid the antenna wire on the ground and I stepped off the length – 25 paces. So the antenna wire was 75 feet long. We took it back to the house and cut off 10 feet of wire. We then did three runs for shortening the length. Ended up at 62 feet long. Nice resonant point in the 40M and 20M bands, with nice wide bandwidths. The antenna was resonant at 21.8 Mhz on the 15M band and a little high on the 10M band. We will need to trim the 15M and 10M stubs to get them to where they need to be.

    73
    Clint

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