how i can vary the range of tws 434?

hello friends.....
i m working on a wireless project in which i m using tws-434 and rws-434.
can u plz suggest me how i can vary my distance of transmission?
if i want to use a potentiometer then how it will help me exactly?

1)change the vcc of Tws
2) put attenuator for either TWS/RWS or both

bro i will use tws&rws434 to trasnmit data serialy databy using mcu.
brother can i connect my tx or rx directly to my mc tx or rx pin? is there any need for intermediate circuitry?coz i am would be transmitting temp and fire statues serialy kindly help