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Old Feb 03, 2012, 08:39 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,567 Posts
Mini-HowTo
10 dbic Crosshair antenna

For a full tutorial, please go here: http://fpvlab.com/forums/showthread....enna-tutorial!

This is the new Crosshair antenna developed as a joint effort between HugeOne (www.trueRC.net/Canada) and me (Video Aerial systems). It is a nice 10 dbic and incredible .98 axial ratio. Fits nicely on your tracker too!

We encourage hobbyists all over the World to try their hand at this design. While Hugo and I do open source this, we politely ask that it not be copied for commercial sale. We worked very dillignetly refining this design and we ask that you honor our work.

Below are the dimensions of this antenna for quick reference. However I put the build details only on FPVLAB under the VAS forum. The details on this antenna is critical, so I suggest you read the tutorial.

Materials needed:
1 sheet of copper or galvanized steel plate (I used galvanized steel)
1 Copper tube either or 3/8 (if using a balun build method)
1 coaxial cable
2 pieces of MIG welding wire or Memory wire.
4 nylon bolts
4 nylon nuts

Calculations:
Wire diameter in inches = 42/f in MHz to 60/f in MHz
Height over reflector in inches = 2350/f in MHz
Length of copper tube = 2933/f in MHz
Size of reflector panel in inches= 8800/f in MHz to 17500/f in MHz (larger reflector increases gain and F/B ratio)
Short leg length in inches = 2490/f in MHz
Long leg length in inches = 2945/fin MHz


If you want to buy them, you can find these at Ready Made RC, True RC, and Urban Drones

Have fun building!

-Alex
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Last edited by IBCrazy; Mar 02, 2012 at 09:08 PM.
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Old Feb 03, 2012, 10:50 AM
CEL abuser
USA, CO, Denver
Joined Dec 2010
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The mad scientist emerges from his lab with another awesome creation!
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Old Mar 02, 2012, 06:01 AM
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Sydney, Australia
Joined Jun 2006
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what antenna works best with is on the tx side? I currently use a cloverleaf.
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Old Mar 02, 2012, 09:11 AM
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Canada,Quebec
Joined Jan 2005
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Quote:
Originally Posted by Gree View Post
what antenna works best with is on the tx side? I currently use a cloverleaf.
Cloverleaf, windmill, skew planar wheel, turbine... as long as they are same polarization direction (RHCP >> RHCP) and good SWR match.

-Hugo
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Old Mar 02, 2012, 10:42 AM
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
i just flew my quad 2000 feet away, behind roughly 60 feet of treeline. 10DB crosshair and lawmate 500mw TX on 2.4ghz. Really really great antenna. I used a CL on the transmitter:

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Old Mar 02, 2012, 10:56 AM
Just trying to get a nut.
scrtsqrl's Avatar
United States, VA, McLean
Joined Oct 2006
6,469 Posts
Will enclosing it in a Tupperware plastic box degrade performance?

Thanks for your awesome work.

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Old Mar 02, 2012, 02:43 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by scrtsqrl View Post
Will enclosing it in a Tupperware plastic box degrade performance?

Thanks for your awesome work.

Not much. The thinner the plastic, the better.

-Alex
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Old Mar 02, 2012, 03:53 PM
Just trying to get a nut.
scrtsqrl's Avatar
United States, VA, McLean
Joined Oct 2006
6,469 Posts
Quote:
Originally Posted by IBCrazy View Post
Not much. The thinner the plastic, the better.

-Alex
Sweet.
This one, as you said is less cumbersome than the helical. I'm sold!
Thank you.
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Old Mar 03, 2012, 06:37 AM
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Gree's Avatar
Sydney, Australia
Joined Jun 2006
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Quote:
Originally Posted by Hugeone View Post
Cloverleaf, windmill, skew planar wheel, turbine... as long as they are same polarization direction (RHCP >> RHCP) and good SWR match.

-Hugo
Great thanks very much...
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Old Mar 09, 2012, 07:37 AM
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Australia, WA
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Whats the Beam width?
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Old Mar 09, 2012, 07:42 AM
Team White Llama!
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65 degrees for 10dB i beleive
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Old Mar 09, 2012, 07:52 AM
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Australia, WA
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Quote:
Originally Posted by gundamnitpete View Post
65 degrees for 10dB i beleive
Cheers
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Old Mar 09, 2012, 08:32 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Beamwidth:

55 degrees at 7dbic
90 degrees at 4dbic
120 degrees at 0 dbic

What this means it that the singal is just as strong or stronger than a skew wheel within a 105 degree beam.

-Alex
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Old Mar 09, 2012, 09:08 AM
Pat K
The Netherlands
Joined Dec 2010
382 Posts
Would this antenna work well at 5.8GHz?
Does the difference in height between the center conductor and shield conductor matter? I guess in theory it should be 0 and will be more critical at 5.8GHz.

Regarding the matching balun, are the diameter/thickness of the tube independant from the frequency as well as from the size of the RF cable?
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Last edited by Papat; Mar 09, 2012 at 09:32 AM.
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Old Mar 09, 2012, 09:28 AM
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Joined Jun 2010
561 Posts
this antenna is not working very well on 5.8 at least no one hast yet build a working one. But I would not say its impossible.
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