ENG - Communications - Building UHF 433 Antenna

With some metal dipsticks, for example, disposable dry cleaning hangers, you can build for free a Yagi antenna to receive UHF signals.

UHF Yagi antennas are the most common antennas... the roof TV antennas. Taking a look in an store you can find them with prizes from 15€. The problem is the frequency they are designed. Starting at 470 Mhz up to 862 Mhz. A little bit high for our purposes. If you want to buy an specific UHF 433 Mhz antenna then the prize increase to 50€ a 3 directors one, and the interesting for us, 5 or more directors are around 75€ to more than a hundred.

However, to do a Yagi antenna is not complicated if you take care measuring distances and sizes. You can find lots of tutorials surfing the web. In our case we are going to use a free downloadble software called VK5DJ's YAGI CALCULATOR

Pressing ( Task - Design Yagi ) and having all the materials you can fill all the items.

Pressing Calculate you have the results having all the measures with a 0,1 mm precission indicated.

Now it's time to build it! Having all the measures we can start cutting material. First the Reflector, Radiator and Directors. We used 6 mm round Brass for Reflector and Directors and a flat Brass 7,5 x 3 mm for the Radiator (Figure 1). To turn the radiator we used a pipe bender but having a pipe or something round of the diammeter you need you can bend the material.

To build the boom we had decide to use a simple square piece of wood but finally we take a different decission. Recycling wood sheets of a curtain (Figure 2) to build a light boom.

Using the distances indicated in the Yagi Calculator we start measuring and marking the position of all the Directors, Reflector and Radiator (Figure 3) after that we mark the center of the sheet (Figure 4) and we cut the exceed of wood (Figure 5). Then we drill the position of all the items of the antenna (Figure 6).

To fix properly the pieces of wood first we sand the two sheets (Figures 7 and 8). When it is finished we cut the square wood where the directors etc will be positioned (Figures 9, 10 and 11).

Now we have all the pieces to start fixing (Figure 12) First of all we put a film paper because we want to fix the pieces togheter... not to the table (Figure 13). then we put the pieces first the preholed sheet (Figure 14) and then the square pieces of wood (Figure 15) and finishing with the last wood sheet (Figure 16) and fixing it with tweezers (Figure 17).

And now keep calm (Figure 18) We have to wait for the glue to take effect.

Welcome again! now we have the piece finished (Figure 19) it's time to drill the boom.

After drilling the boom (Figures 20 and 21) we can preassemble the antenna (Figure 22). To fix the radiator we need an extra of wood, a sheet of 10 mm width is perfect (Figure 23) because the square piece was of 30 mm (Figure 24) and our boom is 50 mm of diammeter (Figure 25).