How to build a 5.8GHz Helical Antenna by Danger Mouse

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Posted: June 6, 2012  |  18,197 views
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How to build a 5.8GHz Helical Antenna

Introduction

A helical antenna consists of a conducting wire wound in the form of a helix mounted on a reflector (Figure 1).


The two key advantages to this design are circular polarization and high gain. In simple terms this means you can bank your plane without losing image and you can fly a long way away. The following instructions will help you construct just such an antenna.

Please check out forum for complete instructions.

Parts List

Part

Part Code

Price

Blank Fibreglass Printed Circuit Board

HP9514

$3.95

1/16in Copper Round

KSE1176

$3.35

Copper Sheet

KSE0259

$17.00

SMA Reverse PCB – Plug

PP0594

$9.95

Total

$34.25

Tools Required

  • Bench Drill
  • Hacksaw
  • Side Cutters
  • Soldering Iron
  • Stanley Knife

Miscellaneous

  • 15mm Ø Dowel

Build

Step 1: Print Guides PDF

  1. Print out Guides PDF and cut out Forma and Reflector Templates marked in blue.

Step 2: Construct coil

  1. Attach Forma Template to 15mm Ø Dowel.
  2. Wrap 1/16in Copper Round around 15mm Ø Dowel marked in black to form coil.
  3. Using a pair of side cutters, cut where indicated (Figure 2).



Step 3: Construct Reflector

  1. Using a hacksaw, cut a 50mm x 50mm square from Blank Fibreglass Printed Circuit Board.
  2. Attach Reflector Template to 50mm x 50mm square.
  3. Using a bench drill, drill 1.5mm holes marked in green and a 3mm hole marked in red.



Step 4: Solder SMA Reverse PCB-Plug to Reflector

  1. Remove Reflector Template and insert SMA Reverse PCB–Plug into rear of reflector (Figure 4).



  1. Using a soldering iron, solder pins where indicated (Figure 5).




Step 5: Construct Wavetrap

  1. Using a Stanley Knife, cut a 3.2mm x 6.4mm rectangle from Copper Sheet.
  2. Using a soldering iron, solder rectangle to coil where indicated (Figure6).



  1. Using a soldering iron, solder coil to remaining pin where indicated (Figure7).

You’re good to go!

Thank God for IB Crazy

Comments

Danger Mouse June 11, 2012
Hi Luka

Thanks for the comment. There are two reasons that I can think of for not using a spring. First and foremost, a spring is made from spring steel which doesn't lend itself well to being reformed. Secondly, copper is a fantastic conductor which is what you want for an antenna.

Regards

DM
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rollinolin July 27, 2012
what does the diameter have to be? is 15.5 to 15.6mm too much? What are the limits?

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Danger Mouse July 27, 2012
Hi rollinolin

I would suggest using 15mm or slightly smaller. The critical factor is the material you are going to use to form your coil. If you find after winding it that it slightly expands then by all means use a forma less than 15mm. Hope this helps.

Regards

DM
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Luka Carl June 11, 2012
why not find a spring of a same diameter, and compress it to the correct pitch. easy and exact
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schraut5 June 17, 2012
Very cool! Thanks for posting

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Danger Mouse June 19, 2012
Hi Kiwi Carl

The first 1/4 turn of the coil does not sit 2mm above the reflector because I've found that given the size of the 5.8GHz helical it was impractical to achieve. Just my personal experience.

As for the 0.8mm MIG Wire. I would suggest this would be too thin. Most hobby shops stock 1/16in Copper Round and it is inexpensive.

I hope this helps.

Regards

DM
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Luka Carl June 24, 2012
Can you provide some background math involved to help me get the dimensions to construct such an antena for the specific channel (tuned) lets say 5860Mhz (channel 7 on fatshark/immersion)?
What kind of gain is expected and what is the usefull angle on these?
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Danger Mouse June 24, 2012
Hi Luka Carl

The Helical Antenna is wide band. In simple terms this means the above design will suite numerous channels/frequencies in the 5.8GHz range.

Gain is affected by the number of turns. The greater the number of turns the higher the gain. Ideally Helical Antenna's are in the region of 3 - 12 turns.

The angle of the antenna depends on far away you intend to fly and how high. To give you an example, if you fly 8km away and in the region of 250m - 500m high then your antenna should be at an angle 2.5 - 5°.

I would highly recommend reading IBCrazy's thread on Helical Antenna for a more in depth discussion.

Cheers

DM
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Luka Carl June 24, 2012
I meant the angle of radiation. So the more turns I make the higher gain I get and the narrower the angle of radiation?
Does it matter if a use a copper sheet and not the pcb one? Is 1.8mm wire still ok?
Thanks
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Danger Mouse June 24, 2012
Hi Luka Carl

Yes you are correct, the more turns the greater the gain but the narrower the angle of radiation.

Yes copper sheet will do fine. Just make sure that it is relatively stiff so as not to deform.

Yes 1.8mm copper wire will do fine. The thicker the better generally speaking.

Hope this helps.

Kind Regards

DM
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kiwi carl June 19, 2012
Hey DM, I'm new to helical antennae but I've noticed in other versions that the bottom of the coil runs parallel to the reflector board 2mm above (or so) for 1/4 of the coil, yours does not... why is that? Also, is .8mm Mig wire ok to use? Thanks mate, Carl.
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colorex June 7, 2012
Thanks for posting this here!
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rollinolin July 27, 2012
Where the hell do you get a 15mm dowel. I got a 5/8 inch dowel thinking it would be close but caliper says its 15.45mm
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Danger Mouse July 27, 2012
Hi rollinolin

I found some in a mates shed. You could ask a friend with a wood lathe to turn a piece up. You could look at another material all together such as plastic or alloy. Hope this helps.

Regards

DM
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Timot June 10, 2012
Great !
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Soldier53 December 30, 2012
Thank You, looks straightforward. great job.
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alcoxy March 30, 2013
Hi Danger Mouse,

Thanks so much for posting this tutorial, I'm going to get onto making one of these soon for my 5.8GHz FPV system too. I am using the fatshark goggles and just bought these (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=27750). Would the antenna you have built above be a good substitute for the skew planar from Hobbyking in the link above? Is it the right kind of 'handed polarisation'?


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tb0384 September 11, 2013
Hi guys, can I leave the dowel in to support the coil? If so, can I then cover it in electrical tape or Kapton tape to keep the coils protected? Thanks in advance... Tony
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larz001 March 1, 2014
I have some k&s 1/16 brass round, would this work as well as copper wire, or should I stick with copper?,, I also have thin brass plate 0.8 mm thick, would this work for the reflector?
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Longbow August 28, 2014
Hi I have been doing some research on the best way to build helical antennas and happened across a page that shows the best way to build the reflector (or ground conductor). Seems that everyone is doing it wrong (or at least not as well as it could be). Even the $80+ antennas don't use a conical reflector which adds a further 3DBI gain at least.
http://users.ece.gatech.edu/~az30/Downloads/Helix_EuCAP_07.pdf
...is the page that shows how it works and the dimensions required.
http://flitetest.com/articles/Video_TX_RX_Frequency_Chart
...shows the frequency length of whatever frequency you use.
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debasish March 15, 2014
can i use aluminum wire of 14awg or 1/16 inch inplace of copper wire??
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Longbow August 28, 2014
If you can solder aluminium...
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