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I do not know much about antenna's. A wire broke off of a Wifi antenna, being part of a video transmission unit of a quadcopter.

enter image description here

The short grey colored wire on the right side of the picture broke off. I simply tried soldering it back on. But that does not seem to work. The range of the antenna now is not even 2 meters. The thick shrinkwrapped black part of the antenna is a holow metal tube.

I assume that the center of the antenna is going through the tube, while the outside of the antenna should be attached to the tube. But this is just a guess of mine, I have not much knowlegde about antennas.

The black antenna wire is so small that I can not see a distinct core or shield. Is this a coaxial wire? How should it be attached to the metal tube? In other words: How could I fix this antenna?

Thanks.

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Frequency is not given, but this looks like it could be based on a quarter-wavelength antenna main element (your broken wire), and a quarter-wave sleeve balun element:

sleeve balun antenna


Coax cable extends into the left end of the metal sleeve, which is hollow. The left end of the sleeve is electrically floating, unattached to anything. The right end of the sleeve is attached to the coax shield.
Coax centre conductor is attached to the quarter-wave antenna wire, where it appears at the right end of the sleeve.

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This looks like a basic 1/2 wavelength dipole antenna, similar to the one shown here, with the central element broken off. It may be difficult to solder it back on without shorting it to the metal sleeve to which the braid of the coax cable is connected.

A better idea is to find a spare coax cable with the right connector (or just shorten the existing one), peel off 1/4 wavelength (about 3 cm or 1.2" for 2.4GHz) of the braid, and then crimp or solder the sleeve to the coax braid so that the central element is sticking out:

enter image description here

If attaching the sleeve is too difficult, you can simply solder another 1/4 wavelength piece of wire to the sleeve, and make it point in the direction opposite to the central element.

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