Oh, you mean the antennae for the alarm itself. It should just be either copper or aluminum wire, AWG 20-22 or something, right? You can just either replace it with stranded wire, or solder an extension on. But the length is usually determined by the frequency of the signal being sent to/from the unit. It may screw up the signal, so I would make it so that you can put it back if it doesn't work.
well heres the deal, the range on the alarm sucks. its mostly the fact that i have to hold the remote right up against the car to get it to recieve the signal. this is my second one and it has the same range problem. how can i increase the range of the alarm reception?
What I did years ago when I had aftermarket alarms, I would make the end of the antenna as high as possible. I would just take some tape and tape it up way up inside your dash. Keep in mind though that metal causes interference. Also, if you are to far away you can always hold the transmitter up to your chin and then opperate it. This uses your body to amplify the signal somehow. It works beleave it or not.
It might sound stupid, but have you called the manufacturer yet? They may be able to offer some suggestions. sfblacksel has a good suggestion about the mounting point. High and away from the frame. As you know, the frame is the ground for the whole car, and all that power going through it will surely mess up an RF transmission.