Channel Bonding

[katsumi_seki]

Does Channel Bonding generally affect communication distance(radio distance)? If the distance of the Rx and Tx are far away from each other, which channel(20MHz,40Mhz,80Mhz...) should be used?

Plus, if I use P300 for long-distance communication and the distance is within 1km, which channel should I use? 

Thank you