capturing (and decoding) open wireless network packets

hello,

i am trying to capture my open wireless network's (no password) packets.

I am able to capture wpa2 traffic and decrypt the packets with it's password. but, when I capture open wifi traffic, i cannot see any readable packet in the capture file.

I am using: -backtrack 5 -AWUS036H card (Realtek RTL8187L chipset)

i tried: "airdecap-ng -b <ap_mac> <capture_file.cap>"

but it didn't work.

How can i decode/decrypt/decipher the "open wifi" packets?

Thank you,