Jan 052012
 

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

Jul 122011
 

A last helix to cover all interesting frequencies for FPV.

Antenna dimensions:

  • Design frequency 2450MHz
  • 8 turns
  • Wavelength 0.23
  • Internal diameter 41mm
  • Wire diameter 2.5mm
  • Coil spacing 28mm
  • Reflector diameter 80mm
  • Wave Trap size 15.2mmx7.6mm
  • Feed point height 5mm (wire center), see pictures
Jul 082011
 

This is an example how one can hit the target on spot with a clean build even on 5.8GHz.

Antenna dimensions:

  • Design frequency 5800MHz
  • 8 turns
  • Wavelength 0.23
  • Internal diameter 17-17.5mm
  • Wire diameter 1mm
  • Coil spacing 11.8mm
  • Reflector 40mmx40mm
  • Wave Trap size 6.5mmx3.2mm
  • Wave Trap spacing from feed point 2mm
  • Feed point height 2.5mm (wire center), maintained over 1/4 turn
Jul 052011
 

Just finished with my helix antenna, designed for 1240MHz.
Used the helix calculator from http://jcoppens.com/ant/helix/calc.en.php.
Parameters were 1240MHz, 8 turns, 0.23 wavelengths.

My internal helix diameter is roughly 80mm with a coil spacing of 55.5mm. Wire diameter is 3.5mm/10mm².
Reflector size is 250mmx250mm. Center support is made from 6mm Balsa, soaked with epoxy resin.
For matching the IBCrazy wave trap method is used. Trap size is 30mmx15mm. See also http://www.rcgroups.com/forums/showthread.php?t=1377791

 

Mar 082011
 

The first recorded FPV flights I made for antenna and range testing.

Tested the following antenna combinations for video downlink:
1. Flight: Skew-Planar-Wheel on video TX+RX
2. Flight: Inverted-V on video TX and Yagi on RX
3. Flight: Inverted-V on video TX and skew-Planar-Wheel on RX
4. Flight: Inverted-V on video TX and Yagi on RX, pointing in other direction