ipad 06.15.00 baseband downgrade iphone 3gs

[dave.dave]

when i tried to upload the firmware my iphone is currently running redsnow shows a message "this device does not support untehered jailbreak". what does this mean? should i upgrade from 4.1 to 5.1 before i downgrade? I have tryed this about 5 times now and the bb stays on 06.15.00 and the phone shows no signal. any help would be greatly appreciated

[dell_xps]

Have you got the phone switched off when trying to downgrade the BB ?, has to be switched off to start off with m8.

[dave.dave]

yes phone is switched off and in DFU mode.