Making a UHF 433mhz Inverted Vee Antenna Set

Here's a quick guide to build your own Inverted Vee antenna.

Calculate the length of antenna you need for a 1/4 wave antenna. This calculator is awesome:

http://home.comcast.net/~wxtofly/wavecalc.htm

I used 433mhz and a 95% velocity factor. You could pair your OpenLRSng Rx/Tx and read the exact frequency to tune the antenna precisely to the frequency you're using.

The dipole antenna uses 1/4 wavelength per wire, so each wire will be 164mm measured from where the shielding ends. Cut your wires slightly longer before attaching, then trim them to length. I cut mine at 18cm.

Parts

You can use any wire for this, but I'm using 22awg (that is .025" diameter) lacquered wire.

For the SMA connector, I've taken the stock antennas that came with my OrangeLRS TX/RX, removed the plastic casing and de-soldered the existing coiled antenna from the coax. I then put some heatshrink around the base of the connector and soldered on the laquered wire.

Protip for soldering laquered wire, turn your iron up to 700 or 750 degrees and put a blob of solder on the iron. Touch and hold the blob to the wire until you see the lacquer burn off. Tin the wire as normal.

Build

  • Solder one wire to the shielding and one to the center pin of the coax. Here's what it looks like after re-enforcing the center pin solder with some heatshrink.
  • Trim the wires to exactly 164mm, measuring from where the coax shielding and center wire separate.
  • Here I've covered the wire with some thin (2mm) tubing and then coffee stirrers. The tubing is cut to 170mm to cover the 164mm wire.
  • I have the wires taped to a ruler to get the recommended 120 degree angle between the wires.

  • Using arcsin 60 degrees = .866 we get an "opposite" side length of 147.22mm for a distance between both antenna tips of 170mm * .866 * 2 = 294.4mm

  • Cut a support out of an old hotel key card, any rigid plastic will do, and hot glued the antenna to the plastic:

I built a matching antenna for my transmitter, but maybe a 1/2 or 1/4 wave monopole would be better? Any suggestions?