For those who may have the same problem as I had with Hercules WiFi PCI 802.11G card.
This card uses a Ralink chipset.
Indeed, "lspci -n" returns :
02:0b.0 Network controller: RaLink RT2561/RT61 802.11g PCI
Subsystem: Hercules Unknown device 0050
Flags: bus master, slow devsel, latency 32, IRQ 20
Memory at ea000000 (32-bit, non-prefetchable) [size=32K]
Capabilities:  Power Management version 2
The chipset is well detected by FC7 and module rt61pci is automatically added in modprobe.conf.
However the connexion does not work as if.
So, you just have to add the following file in /etc/yum.repo.d :
Name this file "kwizart.repo"
Then type "sudo yum --enablerepo=kwizart install rt61-firmware"
The rt61pci module should now work fine !