You can remove the little RP-SMA connector and put on a wire antenna if you like. Just make sure you make it the right length for the frequency you're using. Solder the wire to the middle of the 3 antenna pads. Alternatively it should work fine to just solder the wire antenna onto the middle pin of the 3 pin RP-SMA connector where it connects to the board while leaving the connector in place. That will allow you to easily remove it later if you want to use a RP-SMA antenna again.
The prototypes came with wire antennas so I've been flying these radios with a wire antenna for a while, and it certainly works well for small planes. I even used a wire antenna for my 7.6km long range test.
Thanks Tridge, that's just what I needed to know.
So what are the right lengths of wire for the two frequencies of 3DR radios sold on diydrones? Do you happen to have any pictures of your simple wire antenna's to get the idea? Do they work just as well ?
What you want is a "quarter wavelength". That comes to about 8cm for a 915MHz radio, and about 17cm for a 433MHz radio.
I find the wire antennas do work well. I don't have any comparative numbers as I don't have the right sort of equipment to do accurate testing, but I've certainly been happy with my wire antennas.
Look in the 3DR wiki page under the amplifier section for a picture of one of my radios with a wire antenna.
You mean that little white wire? Would that work on both the "air" and "ground" module?
yep, that's the antenna. It works at either end.
I have a problem with rf noise coming from the xbee causing servo jitter. How can I remove the white wire antenna and relocate it away from my servos?
There's a simple solution... I wouldn't unsolder your SMA connector!
Just take a pigtail from something you have laying around or order a cheap one from ebay. By "pigtail" I mean a piece of coax cable with a RP-SMA connector on at least one end.
Cut the cable as needed. Figure this by adding antenna length + any distance you want from the radio to the outside of your plane. Now strip off the shield the proper distance for your frequency from the non-SMA end. Optionally shrink tube it a bit for added durability.
RC receivers often use this method. This way you have a better antenna that is more easily placed properly and you don't have to remove anything from the board. The "antenna" is the end length of coax where you have removed the shield.