The specification for the recever: 

• Type: R81 - D8 Nano Sbus Receiver
• Channels: 8
• Frequency range: 2400-2483.5Mhz
• Power input range: 4.5-6V
• Signal format: Frsky D8 Compatible
• Output format: SBUS
• RSSI: RSSI on Ch9 of Sbus Output
• Range: more than 1km
• Antenna length: Approximately 6cm
• Size: 17x11mm
• Weight: 2 grams