Simple DIY Dipole

 

It's possible to make an effective dipole using parts that you are likely to already have or that are available at your local DIY store. The construction methods used can be easily adapted to other antenna designs such as beam or halo. These parts are suitable for a 2m dipole centred at 145Mhz

The full 2m version is at the top of the page with a closeup of the centre below.

 


Required parts

  • PL259 Plug - or something better suited to your radio
  • Coax (RG58 works well enough)
  • 34mm PVC waste Pipe
  • 1m of 5mm threaded rod (or 2x 50cm lengths)
  • 2x M5 washers
  • 4x M5 Nuts (Wingnuts or Hex nuts - I usually use 2 of each)
  • shrink wrap (optional)

Required tools

  • Drill with 4.5 and 5.5 bits
  • Soldering Iron
  • Junior hacksaw File
  • Spanners
  • File
  • SWR meter (or VNA if you're feeling rich)

 

  1. First cut the pipe to a length you want to use, I would suggest the minimum length to use is 20cm.
  2. At one end drill two 4.5mm holes oposite each other. These should be about 2cm from the end of the pipe and are used for mounting the dipole elements.
  3. Another 1-2cm in drill a 5.5mm hole (or suitable size for your coax. ou might want to try making this at a sligt angle.
  4. Determine the length needed for around 12 turns of the coax and after that distance drill another 5.5mm hole. For my RG58 this is around 6.5cm further in.
  5. Push the end of the coax through the first hole. With a short end exiting the dipole end.
  6. Loosly wrap 12 turns of coax around the pipe and pass the spare end through the 2nd hole (you will tighten this up later).
  7. Strip the short end and optionally add some strink wrap to the braid.
  8. On the short end solder a washer (or wingnut) onto the striped ends of the coax (centre and braid).
  9. Add a suitable plug ono the other end of the coax.
  10. Cut the treaded rod to a suitable length (see section below)
  11. Add a nut (or wingnut onto the threaded rod (if it's a wing nut put it on wings first)
  12. screw the rod through the 4.5mm holes you drilled
  13. add the washers and nuts on the inside of the rod.
  14. Tune the antenna and trim as appropriate

 

The Rod needs to be cut to roughly the right length. As with all antenna designs its best to start off too long as it's easier to remove excess metal rather than add it back on. Each element is a 1/4 wave length long. Applying 300/f will five you a full wavelength in meters for a frequency in MHz. This will give you just over 2m for 145MHz. Dividing this by 4 gives a quarter wavlength of just almost 52cm, luckily the speed of light in an dipole antenna is reduced so we can reduce the length to 95%. Calculations give the length to be just over 49cm. Hence cutting to 50cm gives us something to trim off.