Instructables
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Picture of interfacing u.fl connectors
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This is about how to use a transmitter / receiver component that uses a communication protocol, like this WiFly rn-xv, or this xbee pro, which doesn't come with a mounted antenna.  It does have a u.fl connector.

Here's how to interface this component with a proper antenna.


 
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Step 1: What is a u.fl connector?

Picture of What is a u.fl connector?
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It is a mini coaxial cable connector designed for high radio frequencies up to 6GHz, which means that is has a wire conductor in the center, surrounded by an outer conductor, and an insulation between the two, called a dielectric layer.  Wifi, being 2.4 GHz transmission, often uses a u.fl connector as an adaptor wire for the antennas. 

You can see that the male connector is surface mounted on the pcb of the xbee and wifly rnxv. The female connector is on the end of the coaxial cable. 

Step 2: What you need

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If you have a component with a u.fl connector, what do you need to get its signal properly transmitted? 

You need an adaptor cable that goes between the male u.fl connector mounted on the pcb, and you need an antenna. 

But: You need the connection between the antenna to match the connector on the u.fl adaptor cable and there are a few types. 
Just make sure that these match.

How to choose an antenna:
You can use an sma antenna or an rp-sma antenna.
Match the frequency of the antenna rating to your component frequency (2.4 GHz for both the aformentioned xbee and rnxv components)

for the SMA antenna: get an SMA antenna and an SMA to u.fl interface cable adaptor. 
for the rp-sma antenna: get an rp-sma antenna and an rp-sma to u.fl interface cable adaptor.

For this instructable, I'll use an SMA antenna with an SMA to U.fl adaptor, but you can substitute and RP-SMA antenna and an RP-SMA to u.fl adaptor cable. 

Step 3: Attach the SMA antenna to SMA-u.fl cable adaptor

Picture of Attach the SMA antenna to SMA-u.fl cable adaptor
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Screw in the male end of the SMA coaxial antenna to the female SMA end on the adaptor cable. 

Step 4: Attach the u.fl connector cable

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Delicately but firmly, snap on the female u.fl connector on the end of the u.fl - SMA adaptor cable to the male u.fl connector, surface mount soldered onto your PCB. 
qonnor2 months ago

Wouldn't it have been better to include how one would go about afixing the female U.fl conn. to the cable? Does one solder the single internal wire? If so, is there some "thing" called a single thin leg solder tip, or perhaps a Spider Leg soldering iron? Yeah! for those especially tiny jobs. I do appreciate the very clear and concise instructions for putting the cable on the device. Interfacing. My Great,Great Grandson thinks that I should stop doing these things that I know I can't do, Well, that "He" knows I can't... Ya Da Ya Da.... I make him stand there and watch me shake, flutter and F*rt while I peer into a long thin battery lit portable microscope pretending that I can't see. Also, it has become mandatory to answer every question he has by politely saying "What"?, and drop the hot soldering iron in my lap just to get a reaction while he screams and jumps and makes a fuss with "You're going to burn the house down!! I always thank him profusely and say "Jimmy, Someday all this will be yours". At my age we call that, "Living it up".