Hi Stefan,

 

three of the frequencies seem to be the alternate frequency set of the Alpha (RSDN 20) navaids, mentioned on

http://www.vlf.it/alphatrond/alpha.htm

 

F6  12500.00000  Hz = 16 x 781.25 Hz

F7  13281.25000  Hz = 17 x 781.25 Hz

F8  15625.00000  Hz = 20 x 781.25 Hz

 

There also seems to be another one somewhere around 12.75 kHz.

Best regards,

Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: Stefan Schäfer <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Mo., 1. Aug. 2011, 12:55
Betreff: VLF: strange transmissions

VLF,

There are strange transmissions near 12.4, 13.3 and 15.6 kHz, narrow 
band, very strong here in Heidelberg 
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html and 
also in Iceland 
http://simnet.is/halldorgudmunds/TF3HZ_VLFgrabber/index.html, also very 
clear at http://www.ok2bvg.cz/vlfgrabber/ and others.

Does anybody know what it is? Looks different to the often seen 
staircases during transmitter tests...

Unfortunately many VLF grabbers are paused / OFF these times...

73, Stefan/DK7FC