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DIY 7 turn 5.8 GHz Helical FPV antenna

This antenna is based very much on IBCrazy's helical designs on rcgroups

I have used it to fly out to over a kilometre with my 25 mW 5.8 GHz system. Click here for a vid of a 1.35 km flight using the actual antenna in the picture with my Antenna Tracker

Instructions

  1. Check you have the tools and materials
  2. Download and print out helical7.pdf which has templates of the components at 1:1 scale.
  3. Make the bits using whatever materials you have using the templates as a guide.

    For plastic and wood parts one technique is to put the template over the material and prick through with a pin. (Wear a thimble or leather glove or wind tape round the pin head). Alternatively use carbon paper, or just cut out the templates a bit oversize and stick em on with Prittstick etc. Drill holes using a drill a bit bigger than your wire.

    For tin parts, cut the templates exact size and draw round them onto the tin using a felt tip marker pen.

    Wear leather gloves and watch the edges when cutting tin!

    Before gluing or soldering to tin, roughen the surface with the wet and dry paper

  4. Prepare the base with wet and dry and glue the helical support mount centrally on the base with CA glue, leaving a slot wide enough for the helical support to slot in

  5. wind around 8- 9 turns of the wire around your former

  6. Decide whether you want a right hand polarised or left hand polarised helical

    (To figure which each is, take a normal wood screw and a piece of wood. Screw the screw in the wood. The screw represents the antenna and the wood the base. The direction of the threads on the screw is the same as the right hand polarised helical.)

  7. Prepare the wire around 1/2 a turn from the end and the impedance match rectangle with wet and dry.

    Tin the impedance match rectangle and the wire and then solder the impedance match on so the long direction is in line with the wire. solder the match on the underneath of the wire so its face will be facing the base when attached.

  8. Feed the wire on to the helical support, checking your polarisation is correct. Carry on until you have the impedance match about a 1/4 turn away from the former

  9. Put the helical support in the slot on the base and check it fits ok. Once happy glue in position.

  10. Strip 200 mm of outer plastic off your 50 ohm coax and bare 3mm of inner conductor. Solder inner conductor to end of helical and sheath to the base

  11. Fly!

Tools

Materials

Descriptionsourcescomments
cyano gluevarious
wet and dry papervarious
1mm brass wirehttp://www.hobbycraft.co.uk/salix-brass-wire-various-gauges/561297-1000Various sources. Actual thickness unimportant but should be easy bend and to solder. 1mm brass works well. Copper wire would work too.
Tin can lid for base and impedance matchTin canAny can will do. The serations don't seem to do any harm. For soldering you will probably need to sand the surface with wet and dry paper.
helical support material. 1.5 mm ply, plasticard etcvariousAnything reasonably thin stiff and obviously non-conducting. And gluable
helical support mount. 3 - 5 mm ply or plasticvariousYou dont really need this, since you can just attach the helical support to the base with a big blob of glue, but it makes it a bit neater and stronger
50 ohm coax pigtail

Search for RG316 SMA pigtail on ebay.

Though you can get higher spec coax,in practise RG316 works well. The difference of a higher spec cable is minimal. You can also get RG316 coax without connector attached and put it on yourself.
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