I suppose you are referring to the Tx Rx modules. The antenna is basically any normal jumper wire..
theres a parameter lamda=f/c=434000000/300000000=1.44
to have the best range, the length of the antenna should be 1/4 of the value of lamda.
so around 36cm should be the length of the antenna (wire)… you will get a good range of almost 30m irrespective of the obstacles.
(use the antennas on both the transmitter as well as receiver side )
Hope this was helpful