I have a few X10 video cameras around my house. A few of them are right on the edge of the reception range. Can I make a better antenna for the receiver ? Or can I buy a better one somewhere ? Thanks for the help.
Your unspecified X10 camera mutation usually comes with what looks like a small patch or panel antenna. It's not. It's a circuit board with a pair of cross polarized dipoles attached. That's crude and fairly low gain (my guess is about -2dBi including circuit board losses). If you disconnect the coax cable, and solder on a 0.141 semi-rigid pigtail, with an SMA, TNC, or N connector on the end, you can attach any antenna that is made for 802.11b/g which uses the same exact frequency range. I can't recommend a specific antenna because you didn't mention what type of coverage or range problem you are trying to solve.
Incidentally, beware of people "war driving" for X10 cameras: