This probably doesn't belong on -net, but:

With 802.11 interfaces, setting the channel is only sensible when
creating an IBSS (via 'mediaopt adhoc' in 2.0) or hostap.  In other
modes, the card searches for an AP to associate with.  Note that 'IBSS
channel' says 7.

Are you trying to do IBSS mode, hostap, or BSS (regular client)?

-- 
        Greg Troxel <gdt@ir.bbn.com>