433MHz Half-wave dipole for LRS

How to make a simple half-wave dipole useful for 433MHz LRS.

You need:

  • SMA Pigtail with your desired coax length, the cable I used is RG316
  • Plastic antenna tube (found some made by Reely here in Germany, 380mm long)
  • Two pieces of wire each 200mm long, I used AWG28
  • Hotglue

Required parts

Mark the center on the antenna tube and use a solder iron to make a small hole in the tube right at the center. Do not cut the tube in half, this will give a better mechanical stability.
Prepare the open end of the SMA pigtail. Keep the feedpoint cap as short as possible.

Prepare open end and antenna tube

Solder the two pieces of wire to the coax open end. Be sure the center wire will not touch the outer shielding.

Soldered wires

Pull the wires through the antenna tube and the coax open end into the tube hole.
Then apply some good amount of hotglue to strengthen this point.

Dipole feedpointDipoleFeedpoint fix

Cut the antenna tube including the wires inside to an overall length of 300mm. Each half of the tube to 150mm.

Overall length 300mmEach half 150mmReturn loss

On my EZ* I sticked the dipole through the wing. On the lower end, the antenna tube (and only the tube!) was cut and put back together using silicon fuel tube (from nitro engines). This way it’s flexible and will not break in case of ground contact during landing.

Dipole on Easystar wing

New Easystar FPV setup

In the last few weeks I simplified my FPV setup drastically. No more antenna tracker and pan/tilt is also gone.

The RX antenna was changed to a new one from China for 15€ and free shipping. This antenna performs best for the price. A range test was stopped at 13km due to lost line of sight. But it’s sure 15km+ can be reached as long as you have line of sight to the transmitter.

The antenna is from eBay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280402380910

Receiver is a standard 1200MHz one, only did the SAW filter mod (descripted here) and added a LiPo volatage monitor with 3 LEDs.