I'm getting a growing number of requests for a how-to on building the simple 433MHz monopole antennas I use for our EzUHF receivers. Alternatively they can also be used on other UHF receivers, so the recipe is somewhat generic. I'd like to illustrate how to build these with a short DIY manual, so here we go:
What you need:
- 2x Right angle male SMA crimp connectors for RG58.
- Two pieces of wire (any wire!) about 20 cm in length, OD should fit within the PVC tubing.
- Two pieces of PVC tubing (servo pushrod sheeting) about 3 mm OD, 17.5 cm long.
- Two pieces of shrinkwrap about 2 cm in length.
Fig 1. All the parts needed to make a pair of EzUHF Sander-style antennas.
How to build the antennas:
Construction is pretty straightforward and starts with stripping one end of the two pieces of wire so the bare copper wire is exposed. Tin the exposed wire and slide it into the right angle SMA male connector and solder it to the slot in the center pin. A fine tipped soldering iron and some small diameter (<0.8mm) solder works best.
Fig 2. Soldering the wire to the center pin of the right angle SMA male connector.
Now we need to cut the wire to length, so it is tuned to 433MHz, this is accomplished by cutting the wire to 164mm (one-six-four millimeter) length *exactly*, measured from where the right angle SMA male connector ends. This is illustrated below in Fig 3.
Fig 3. This is where the wire exits the right angle SMA male connector, measure from here.
All that is required now is to glue the PVC tubing (Nyrod) to the right angle SMA male connector so it provides support for the wire. A drop of CA (cyano acrylate glue) at the end of the PVC tube will do. Slide it into the right angle SMA male connector whilst slowly rotating it to spread out the glue evenly. Any excess glue can be wiped off with your finger (or a tissue). The end result should look like shown in Fig 4.
Fig 4. The PVC tubing glued into the right angle SMA male connector.
Now we need to insert the plastic cap that goes over the center conductor, this is just placed inside, not glued. Then insert the threaded end cap and screw that in tightly. The right angle SMA male connector should now look like pictured in Fig 5.
Fig 5. The right angle SMA male connector fully fitted with the end cap.
All that is left now is to put a piece of shrinkwrap around the base of the antenna, to give the antenna a more professional looking finish. Fig 6. and Fig 7. illustrate the finished antenna.
Fig 6. The finished EzUHF antenna looked at from the side.
Fig 7. The finished EzUHF antenna looked at from the front of the connector.
That's it! It'll probably take you less than 15 minutes to build a pair of these antennas at minimum cost. They perform better than the Active Robots antennas we recommend in the manual and are thinner/lighter as well, hence have less drag than the Active Robots antennas.
Keep in mind that these *NEED* to go directly on the EzUHF receiver connectors, so don't put them out on an extension cable as their performance will suffer.
Good luck with building these antennas!