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When making antenna out of wire, does curling it affect the outcome?

March 11th, 2010 by , under nnmj.com.

  • When making antenna out of wire, does curling it affect the outcome?

    I want to make an antenna out of wire. It's a 433 MHz Antenna used for RF. The wire is made out of components of a cat-5 (Ethernet) cable. Instead of leaving the wire straight out, can I just curl it?


  • Curling it does have an effect. What it does is change the inductance. The effect of this is to change the resonance point of the antenna. In other word, to get it to resonate on the same frequency you would have to shorten the antenna.

    It also has an effect on the aperture of the antenna. A shorter antenna does not 'cut' the same amount of field and so the induced voltage is lower. In other words, a shorter antenna is not as good as a full length antenna.


  • Assuming you're trying to pick up only the 433MHz signal, you would do best using a straight 69.24cm (quarter-wavelength) wire perpendicular to the direction of the signal (usually straight up like a car's antenna).
    Only make it into a coil if you know the direction and distance at which the signal is coming. If the coiled antenna is misaligned, it may not pick up anything at all. If you don't mind adjusting the orientation occasionally, this might not be a problem.

    Also, if you're using a CAT5 cable, make sure you take off the shielding or you'll surely get no signal.


  • Coiling the wire as you explain can definitely affect how well the antenna functions. Depending upon many things, coiling up the wire might make a better antenna or it might make a worse antenna. The subject is too technical and there are too many variables to give you the details of why this is so.


  • Yes, No difference







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