Amateur Radio Propagation Studies by IK3XTV
S.I.D.C. - Sunspot Index Data Center directory (Belgium)
DXrobot
Beaconspot.uk by UK Microwave Group
La chasse au radiosonde

Ripetitori - Repeaters

Elenco ripetitori e link italiani VHF e superiori by IK2ANE
The Repeater Builder's by W3KKC