Build Instructions

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• 1

  Step 1

  Making the Yagi
  

  1) Use the dimension for the elements from the design I posted above to measure and cut the elements. 2mm fencing wire & some small wire cutters does the job, try to get the lengths as accurate as possible.
  
  2) Use a sharpie to draw a straight line on the 6.3mm Bunnings aluminium rod. Use this line to measure out the spacing between the elements and use a good nail to indent the rod where the elements should go so the drill bit catches at this point.
  

  3) Buy a 5/64 (1.98mm) drill bit which is slightly smaller than the 2mm wire creating a force fit for the wire when it goes through the hole in the aluminium rod, making an electrical connection.
  

  4) Drill a 2mm hole at the 410mm point on the sharpie line and use a nail through this hole to secure the rod to a long bit of timber. This secures rod with the sharpie line on the top of the rod and ensures all holes are drilled at the same angle. I didn't do this step when I first tried and the holes weren't all drilled in the same plane, so had to start again.
  

  5) Drill all the element holes, ideally with a drill press which will ensure the bit is perpendicular to the rod and the holes on the other side of the rod will line up.
  

  6) With a small hammer gently tap all the element wire into the drilled holes - ensure the right length wire goes into the right hole.
  

  7) Use a ruler to ensure the wire on each side is equidistant length to the rod, using small taps on a hammer to adjust. Try not to shift the wire too many times in the hole as the aluminium hole will widen which means you won't get an electrical connection and the wire may shift too easily messing up the length on both sides of the wire (i.e. no longer equidistant to the rod).

  Using this technique the holes were perfect and all the elements when fitted had a snug fit and lined up in the same plane nice and straight.

  Spray with galvanising paint to protect the steel (especially as we have aluminium and steel touching which can cause galvanic corrosion when exposed to the elements) and the paint also binds the elements to stop them from sliding (although they should be pretty tight in the hole), it also makes it look good!
  

  8) for the active element I used the coax itself to avoid having to solder an extra connection (never a good idea with RF), and stripped the coax and shield back to make a dipole of the right length, soldering the wire to give it some stiffness and using a small diameter plastic sheath to protect the wire. I then mounted the coax so that the coax ends for the dipole sits in the same plane as the elements.

  9) For the balanced to unbalanced balun I used a 32mm (1/4 wavelength of 2350Mhz) piece of RG213 coax and soldered the braid to the feed coax inner conductor and the other end to the feed braid.

  10) Silicon to seal around the coax ends to protect from the elements.

  11) Used a 30mm plastic conduit (not metal!) to mount the antenna above the roofline and orientate it at 45 degrees and point towards the cell tower (check the modem RSSI values while moving the Yagi around to get the best direction). To mount the Yagi onto the conduit I used the handle from a squeegee window washer that used a rod about the same size as the Yagi boom so it clipped onto the Yagi and the handle end inserted into the conduit.

  Here is a link to a comprehensive LTE Yagi build: http://bcbj.org/antennae/lte_yagi_diy.htm

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