Link

   
HOKA Electronics "Headquarters" The Netherlands
HOKA Electronics ITALIA
HOKA Electronics UK
NSK Frequency Manager
   
IK1YDE - Andrea Gerolla - http://ik1yde.blogspot.com/
Utility DXers Forum
udxf · Utility DXers Forum
Monitoring Utility Stations - Digital Mode
IPS Radio and Space Service
Ary Boender, Numbers & Oddities
Utility Monitoring Central
VLF
Ed Deasy, Analysis RTTY signals
The Italian HF Archive
DRAFT version of the High-frequency Radio 
Automatic Link Establishment (ALE) Application Handbook
International Telecommunication Union (ITU)
Radiofacsimile - Marius Rasenson
HF ASIA
Digital Mode Samples
   
Google