Today I'm planning to solder the antenna for the ChepaBot radio controller. I purchases a SMA to SMA extension cable from Jameco for this. I'll cut the coax cable in half, peel back the inner conductor adn outer jacket, and solder wires to them.
The radios opewrate at a frequency of 434 MHz. If I take that frequency and divide it into 486, I get the proper length of the antenna (which will be a dipole). That comes out to 1.078 feet, or 12.936 inches. Divided in half and I get each element should be 6.5" long.
You can find an antenna calculator at http://www.crompton.com/wa3dsp/hamradio/antcalc.html