Four copper rods are cut from the thick copper wire - it has to be stiff enough to stay straight without support. Aluminium can be used instead.
The rods are then connected to the white conduit box through the four holes at 90 degrees to each other. The holes can be filled with cork, wooden dowling or similar and drilled to a size to allow rods to be pushed through them. Another system is to wrap ends of rods in masking tape until they fit snuggly in the holes. A conduit box (see above) is recommended as this is electrically resistant. A wooden block risks becoming conductive once it gets wet at which point the antenna will not work.
The corks/dowling in the holes can be wood or cork because it does not matter if they get wet - this won’t make a circuit with an adjacent rod because of the plastic inbetween.
The length of the rods is determined by the frequency that we want to pick up. For UHF transmission @ 600MHz, the wires (rods) need to be 12.5cm in length - all four should be the same length
The calculations for this length = 300/600 = 0.5m. This the full wavelength. A dipole is in total 1/2 wavelength, with each element being 1/4 wavelength, so each leement is 12.5cm.