antenna question, help!!!

i'm modifying my electronic wildlife caller a little bit...i'm using is a Nady VHF 151VR wireless series... http://www.nady.com/vrseries_pg.html ...i have the transmitter hooked up to a mp3 player...the transmitter is hooked up to an amp then a speaker horn...it works great but the transmitter currently has a softwire antenna...i want to convert it to something more like a rod antenna that i can attach somehow to the outside of the caller and extend easily...i have no experience with antennas...is it possible to do this?...can i solder the softwire somehow to a rod antenna?...or do i have to detach the softwire from the circuit board and solder in a new antenna?...i'm lost here...thanks in advance

dsf