at first let's take a look for what we need :
1) 2 Arduino Board "I used Uno"
2) RF 315MHz or 433MHz transmitter-receiver module .
3) jumper wire .
4) BreadBoard .
5)External Power supply (9V Battery *2) "Optional" .
Step 1: Module Specification
Working voltage: 3V - 12V fo max. power use 12V
Working current: max Less than 40mA max , and min 9mA
Resonance mode: (SAW)
Modulation mode: ASK
Working frequency: Eve 315MHz Or 433MHz
Transmission power: 25mW (315MHz at 12V)
Frequency error: +150kHz (max)
Velocity : less than 10Kbps
So this module will transmit up to 90m in open area .
Working voltage: 5.0VDC +0.5V
Working current:≤5.5mA max
Working method: OOK/ASK
Working frequency: 315MHz-433.92MHz
Sensitivity: excel –100dBm (50Ω)
Transmitting velocity: <9.6Kbps (at 315MHz and -95dBm)
the use of an optional antenna will increase the effectiveness of your wireless communication. A simple wire will do the trick.