40m BAND LOADED DIPOLE

This dipole is ideal when there is not much space available to install a full lenght dipole for this band. It is only 10 meters long and it's a good compromise that allows you to work 40 meter band.

Diagram and dimensions of the loaded dipole

Bill of materials:

- electrical cable 1,5 mm²;

- two 40mm outer diameter PVC pipes, 16cm long.

Drill a 3mm hole on the PVC support at a distance of one centimeter from the edge of the pipe. Insert the electrical cable into the hole you just made and pull out three meters. This will be the central part of the dipole. Wind 49 turns on the PVC tube, make a 3mm hole at the end of the winding and insert the rest of the cable. Measure two meters of electrical cable from the end of the winding and cut (leave an extra 10cm for calibration). Half of the dipole is finished, now do the same for the other half. If you prefer, you can cover the coil with tape or heat shrink. If you fix the dipole on two fishing rods 5 meters long each, using cable ties, you will have created a compact and lightweight rotary dipole.

The loading coil fixed on the fishing rod

The use of a choke balun is recommended, as always, to match the (unbalanced) coaxial cable with the (balanced) dipole feedpoint and to prevent the radio frequency come back to the braid of the coaxial cable. The bandwidth referred to an SWR of 2:1 is about 50 KHz. The use of an antenna tuner is essential if you want to use all the band.

Central support made with square aluminum tube 15X15 mm and TV antenna bracket. Fishing rods secured with cable ties

The dipole in use together with other antennas (10m dipole and 20m delta loop)