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Thread: 40 meter delta loop problem

  1. #1

    Default 40 meter delta loop problem

    I have just finished a delta loop for 40 meter and up.
    My antenna house and garden is very similar this this :
    http://www.mccormick.uk.com/40%20met...oop/index.html

    after cutting and adjusting the antenna to 7.05 MHz i still get 2.8 swr at that frequency.
    At 14.1 MHz the swr is 1.2 ! (so i guess the length is OK) and on 28.2 1,8 in swr.
    The reports are excellent on 14 MHz and good on 7 MHz.
    But i have a feeling that there is something wrong on the 40 meter band.
    The antenna of this type should hang around 1/8 wave length above ground (5 meters)
    On same pleases i am down to around 3,5 meter so the height is between 5 and 3,5 meter.

    One of the 4 legs of the loop is about 1 to 1,5 meter from the rain catcher (metal).
    Is the high swr on 40 meter because of this ?


    or since the swr i 1,2 at 14 MHz it is an indication of that i need the antenna higher up.
    Is the high swr on 40 meter because of the height above ground is to low ?

  2. #2

    Join Date
    Feb 2008
    Location
    St Thomas Ontario Canada
    Posts
    13

    Default Re: 40 meter delta loop problem

    What balun do you have at the feed point? I would try to get the antenna away from the metal as much as possible too. That amount of metal, your rain gutters etc will have some effect on the antenna.

    A better way to feed the loop, if you wish to use it on other bands would be with some 450 ohm ladder line. Run the ladder line from the feed point down to a 4:1 balun, then coax to the tuner. Make sure you keep the ladder line away from metal objects by at least one foot.

    Your loop should be 140.5 feet in total length. That length is for 7.150. It will still have a good SWR at 7.000 as I have found loops to be pretty broad banded.

    I once ran a 75 M loop, the same way you have yours setup. The highest point off the ground was 29 feet. It ran through a maple tree, to a support that kept it 15 feet off the ground. Then over to another support mast at 15 feet. To another support at 20 feet, then to another tree, then another tree and back to the tower to complete the loop. At the lowest point it was only about 10 feet off the ground. I used insulated 14 ga stranded wire. The SWR was 1:1:1 for the section of the band I set the loop up for. Now it was by no means a DX machine but I managed to work all 50 states on 75 SSB with 100 watts from south west Ontario Canada. I worked some European DX with it also.

    One thing I did notice about my signal was this. Anyone within 150 miles of me thought I was running an amp! My signal was strong within that distance. Most likely due to the fact the antenna was too low in the air for 75 meters. But it was all I could do and it worked!

    By they way, those are nice looking homes at your location. Very nice yards too, lots of trees and bushes etc.

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