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!
Cantenna on tripodcantenna baileys can super cantenna

The waveguide antenna can be used by itself, or in combination with a parabolic dish to make connections over even greater distances.

Step 1.
Select a Can - Calculations indicate that the Can should have a diameter between 70 mm (millimetres) and 110 mm. These are not strict limits, but performance will diminish increasingly beyond these sizes. The required length of the can is dependant on the can's diameter. A Can with a large diameter can work with a shorter length (eg. a coffee can). A calculator is provided below.

  • A smooth metal can is better, irregular and ribbed surfaces can cause internal reflections and scatter radio-waves.
  • Can strength is a good virtue.
  • A fitting plastic lid (preferably non coloured) will help with waterproofing.

tin can antenna design

Standing Wavelength (scientifically written as Lg )

The standing wavelength (Lg) is important ! The diameter of the can determines Lg. Lg 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}

D - diameter in mm

Lg in mm

S - ( Lg / 4 in mm)

L - ( 3Lg / 4 in mm, suggested minimum length)

d - (in mm, length of brass tube/ copper wire)

Step 2.

Measure S (calculated above) from the base of the can, mark and drill small pilot hole, then drill or fashion a 1/2 inch /12mm or 5/8 inch /16mm (depends on the N connector) size hole for the N-type connector.
inside can with copper soldered

Step 3.

Solder a piece of 1.5mm diameter (approx. 12 gauge U.S.) copper wire or brass rod to the pin of the N connector. This will serve as your driven element or radiator. Once in place, cut the wire/rod down to d length (calculated above).

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