for the receiver, it's a good idea to use some type of direction finding anntena. a RADIO-GONIOMETER or BELLINI-TOSI direction finding antenna system is one method that can be built in a compact form. more info about such antenna systems can be found here: **broken link removed**
the advantage to this is that 4 quarter wave vertical antennas mounted on a metal surface, or two crossed loops of wire, can take the place of a rotating antenna. the only moving part is the sense coil in the termination box. as you will see, you need to ignore the "james bond" image of a little GPS-like receiver with a single whip antenna and a map display. while it's possible to do something like that with an APRS transponder, that's a bit more complicated than a simple tracking transmitter (an APRS transponder contains a GPS receiver and a radio modem that sends GPS data to a base station). also keep in mind that a small battery powered device with a small antenna will not have much range, and a larger device with a proper quarter wave antenna will give better results