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  • help with loop antenna

    From ecliptic@logicon@zipcon.com to alt.ham-radio.hf on Wed Mar 21 12:14:28 2007
    From Newsgroup: alt.ham-radio.hf

    Have a need to build a "small loop" antenna. Got some embroidery
    loops. Started to think. I know winding around the loop's form will
    increase the inductance, but
    1) what would be the formula to calculate the length of wire for 10
    meters (or any for freq) when winding the wire around the loop form
    instead of just along the outside surface of that inner loop?
    2) how will this effect the receiving nulls? will it reverse the normal sideways nulling?
    3) what would be the effect(s) if I wound around that inner loop but
    reversed the direction of the winding to have say 4 different windings
    on the same form? I know it would change the inductance but what about
    the capacitance. Does anyone have a formula for doing n different
    winding directions on such a form? What would it do to the bandwidth
    and Q?
    Ralph
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  • From lgadbois@lgadbois@earthlink.net to alt.ham-radio.hf on Thu May 3 02:27:04 2007
    From Newsgroup: alt.ham-radio.hf

    I assume you want to build a loop for direction finding. The design
    parameters are not very critical.

    It isn't necessary to make a round loop. It can be diamond shaped using two pieces of wood or bamboo forming a "t" or cross. The vertical piece of wood can longer so that it can be used for a handle or mast. Nails or screws can
    be used as posts projecting from your frame to support the wire corners.
    This type of loop can be built very quickly. If you want to spend a lot of time building a round loop, that's okay.... but it won't work any better.

    The loop is a resonant 1/4 wave. Because it is a coil and has mutual inductance, the length of wire will be shorter than a 1/4 wave which is
    about 100 inches for 10 meters. The diameter of your loop should be a convenient size. I like to make them about 12 inches in diameter. Two turns around the loop will require about 75" of wire. Work it out so the ends of
    the wire meet at the bottom of the loop at the mast. You will need a screw driver adjustable trimmer capacitor in series with the center conductor on your coax, to be used to peak the loop at the desired frequency. You will
    hear maximum background noise from your receiver at the correct adjustment point.

    Good luck!



    "ecliptic" <logicon@zipcon.com> wrote in message news:4601841d$0$30087$19f6ad23@news.zipcon.net...
    Have a need to build a "small loop" antenna. Got some embroidery loops. Started to think. I know winding around the loop's form will increase the inductance, but
    1) what would be the formula to calculate the length of wire for 10 meters (or any for freq) when winding the wire around the loop form instead of
    just along the outside surface of that inner loop?
    2) how will this effect the receiving nulls? will it reverse the normal sideways nulling?
    3) what would be the effect(s) if I wound around that inner loop but reversed the direction of the winding to have say 4 different windings on the same form? I know it would change the inductance but what about the capacitance. Does anyone have a formula for doing n different winding directions on such a form? What would it do to the bandwidth and Q?
    Ralph


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