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Old Sep 01, 2010, 09:15 AM
Registered User
Australia, QLD, Gold Coast
Joined Aug 2007
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Build Log
How To Build a BiQuad RX antenna

Hi,

I'm making a BiQuad antenna for my 1010MHz receiver refer to information released on the flowing websites.
How to build a BiQuad antenna by Eliot Phillips
BiQuad antenna construction
BiQuad antenna by Prof. Trevor Marshall
Another useful site
I think its a easy to build antenna and provide high gain approximately 11~12dBi.

I am using 300X200mm blank PCB for the base and reflector and 2mm wire for the antenna elements.
I'm using 1010MHz (CH5 on my Lawmate Video link) to keep the second harmonic far from my 2.4GHz control link.

The photos and design (kind of ) and construction method coming soon.
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Old Sep 01, 2010, 10:18 AM
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IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Awesome! I can't wait to hear the results. You might want to build this soon or I might have one built before you I have been wanting to try a biquad for quite some time now. The great thing about antennas is how well they scale.

One suggestion; why not use a sheet of galvanized steel as your reflector?

-Alex
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Old Sep 01, 2010, 10:34 AM
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Quote:
Originally Posted by IBCrazy View Post
Awesome! I can't wait to hear the results. You might want to build this soon or I might have one built before you I have been wanting to try a biquad for quite some time now. The great thing about antennas is how well they scale.

One suggestion; why not use a sheet of galvanized steel as your reflector?

-Alex
Blank PCB is much lighter and its what I have, even for the antenna element I was thinking to draw it on a PCB, it could be much easier to built and keep it in right shape in transportation.
I'm planning to stick the RX unit on the other side of base plate to keep the coax cable as short as possible and the whole thing compact.
What is your suggestion?
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Old Sep 01, 2010, 10:59 AM
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How dependant on a ground plane is the Biquad? I have found my Yagis have great range but also multipath like mad. My patches don't have the range but the video clarity is excellent. I wonder where the biquad stands.
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Old Sep 01, 2010, 02:30 PM
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Here is some photo.

Designing is pretty simple (I think ).
Each side of quadrangles is 1/4 wave, regards to Alex posts its 7125/Freq.MHz in cm.
The reflector size is about wave length.
Wires to reflector distance is 27mm in my antenna but if some one has a SWR meter to find the best distance could help.
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Last edited by Talajouy; Sep 23, 2012 at 11:00 PM.
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Old Sep 01, 2010, 02:40 PM
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Netherlands, NH, Edam
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Looking great, if you lived closer I'd suggest you drop by so we could do a VSWR measurement on the spectrum analyzer and tune it just right.

Cheers,

Sander.
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Old Sep 01, 2010, 02:55 PM
The Fixer
Canada, ON, Mississauga
Joined Jan 2009
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Nice job Talajouy. You may need a brace to hold the rx so the sma connector doesn't break off.
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Old Sep 01, 2010, 04:09 PM
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Joined Sep 2003
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i've made one of them, I used a polystyrene block to serve as a spacer between the plate and the wires.
It worked very well.
My friend has a 8dBi patch aerial and was flying his model. I tuned my setup to his plane and I never had any greyouts.
It was very cheap to make if we compare to the price of a patch...
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Old Sep 19, 2010, 01:50 PM
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Australia, QLD, Gold Coast
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This antenna works just great.
Today I flew my plane 5200m far and 490m hight, not even on flip or noise, clear nice video.
Lawmate 1000mw TX with a Vee dipole antena, Lawmate RX with Biquad.

Its cheap and works great, this antenna cost me less than 5$ and works very well, go ahead and make one for yourself.
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Old Sep 19, 2010, 11:03 PM
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I am working on it It's going to be a while. I am going to be moving into a new house in the next few weeks...
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Old Sep 20, 2010, 03:29 AM
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Congrats for the new house.
I have used blank PCB and it works great.

Lighter, much easier to work with and cheap.
Give a try to PCB this time.

habib
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Old Sep 20, 2010, 04:29 AM
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dimentions on the different frequencies are they available yet ? 900/1200/2400/5800 mhz
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Old Sep 20, 2010, 07:35 AM
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I'll put together a formal tutorial when I get some time. For now use the link. Each length around the quad should be 1/4 wavelength which can be calculated: length in inches = 2808/f in MHz. This should also be the height above the reflector. The reflector should be square.

So here's the quick and dirty dimensions in inches (for metric just multiply by 2.54 to get cm):

Element wire length = 22464/f in MHz
Element height above reflector: 2808/f in MHz
Relector size: 11622/f in MHz

When I do finally get around to building one, it will go on my antenna tracker... if I ever get finished designing it.

-Alex
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Old Sep 20, 2010, 12:11 PM
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United States, MI, Detroit
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Quick question about the coax cable.

So a brass tube can be used for the ground.. does the inner wire need to be anything special?

And I'm assuming you guys are hooking the rx directly to the antenna to minimize losses.. Can the brass tube be turned 90 degrees so the RX can be velcro'd flat to on the plate? This looks like an awesome antenna. I would probably find a plastic case to protect the wire element, just seems too easy to rip off.
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Old Sep 20, 2010, 12:24 PM
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That brass tube used as a base for the center point of antenna, that is why I used a brass tube.
If you can fix the center point with another solution like one of those screws, then no need to use the brass tube, just connect your coax to the antenna, remember the back plate as reflector must be connected to the coaxial shield too.
I have coaxial cable inside brass tube, at the end point I used an SMA connector, you can make the inside coax wire a bit longer then turn the connector.
The performance is awesome.
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Last edited by Talajouy; Sep 20, 2010 at 12:30 PM.
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