Arduino UNO - UARTS and HopeRF Transceiver

Projects Networking, Protocols, and Devices
4

i have some problem with my RF. i used HM TRP RS232 http://www.hoperf.com/rf/data_link_module/HM-TRP-RS232.htm
this is transmitter wiring with arduino mega
VCC (RF) --> 5V (Mega)
GND --> GND
RX --> RX1
TX --> TX1

and i used usb to serial in receiver. but i've got bad data.
please help

this my code
int a;

void setup(){
a=0;
Serial1.begin(9600);
delay(3000);
}

void loop(){
Serial1.println(a);
a++;
delay(100);
}

please help
thanks
sorry for my english