This is the solution in order to make to work the adapters usb wi-fi based on chipset ralink 3070 with slackware 13.37.
Blacklist this modules in /etc/modprobe.d/blacklist.conf
the driver rt2870sta it demands two firmwares: the 2870.bin and the 3070.bin, but the firmware 3070.bin it's not installed of default in a full installation of slackware 13.37,
then I have downloaded the symlink 3070.bin from a debian package with the last ones firmwares of Ralink and I have copied the file 3070.bin in the directory /lib/firmware. I have rebooted with modem turn on and the adapter usb wi-fi connected to the computer and at start of slackware I have seen the led to flash therefore the adapter usb wi-fi it's be recognized also from the driver rt2870sta finally, then in wicd I have put in the preferences in general settings and wireless interface: wlan0 and in advanced settings driver: wext, then instead in the property of the connection wpa1/2 preshared key and I have inserted my key wpa. Enough facts these passages it's connect to Internet to the first blow.
I enclose the link of download of the symlink 3070.bin that's necessary for the connection.