Utility Radio Stations

• Number stations
• Cryptography

listeners

• http://www.udxf.nl/
• http://www.udxf.nl/history.html
• https://twitter.com/i56578_swl
• http://i56578-swl.blogspot.it/
• https://www.hfunderground.com/
• https://www.hfunderground.com/wiki/Main_Page
• http://www.ominous-valve.com/uteworld.html
• http://www.utilityradio.com/

producers

• http://www.hcverbindingsdienst.nl/
• http://vovklict.nl/intercom/

digital mode examples

• http://www.kb9ukd.com/digital/ (Digital Modes Samples)
• http://www.sigidwiki.com/wiki/Signal_Identification_Guide (Signal Identification Guide)

literature

• http://www.klingenfuss.org/
• http://frequencymanager.de/products.html