Hello List Wonder if the sounds that you are hearing are the 'Jet' signals [ENIGMA designation XJT]. A sample exists on either http://reachus.at/enigma or http://groups.yahoo.com/group/enigma2000 In the ENIGMA 2000 newsletter you can read more about XJT. It is available for download from the files section. XJT is very prevalent throughout the entire shortwave spectrum and is probably military in origin. 73 Paul