Waveguide Can-tenna |
Wednesday, 09 September 2009 00:58 |
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The waveguide antenna or 'Cantenna' evolved from the Pringle's can antenna. The Pringle's can, being cardboard, does not last well in the weather and is difficult to secure connectors to. More importantly, testing shows that the waveguide cans work better! Step 1.
Standing Wavelength (scientifically written as L_{g })The standing wavelength (L_{g}) is important ! The diameter of the can determines L_{g}. L_{g} in turn determines the best length of the can and the position and size of the connector. See image above (click to enlarge). Plug the diameter of your can into the form to calculate S, L, and d in the above image: {js} var f_c = 299792458; //constant c - the speed of light var f_Lo = (1 / 2440000000) * f_c; //wavelength in open air function calculate(form){ var f_D = form.diam.value / 1000; //get diameter of can in metres D var f_Lc = 1.706 * f_D; //calculate low cut wavelength Lc var f_Fc = f_c / f_Lc; //calculate low cut frequency Fc var f_Lu = 1.306 * f_D; var f_Fu = f_c / f_Lu; var f_Lg = 1 / (Math.sqrt(((1 / f_Lo)*(1 / f_Lo))-((1 / f_Lc)*(1 / f_Lc)))); form.lg.value = floor(f_Lg * 1000); form.lg_one_quarter.value = floor(f_Lg * 250); form.lg_three_quarter.value = floor(f_Lg * 750); form.lo_one_quarter.value = floor(f_Lo * 250); } function floor(fX){ return Math.floor(fX*1000)/1000; //Reduce to three decimal places } {/js} |