[Lowfer] What type of signal am I hearing on 48.800 KHz

[ToddRoberts2001 at aol.com]

In a message dated 2/14/2008 2:45:43 P.M.  Eastern Standard Time, 
ku4xr at yahoo.com writes:
I am hearing a " unusual to me  " type of
signal on some of the freq's. either some type of
RTTY, or maybe  FSK. I don't know, but no mode setting
on MultiPSK will decode the signal. I  can faintly hear
it at 37.500 ( Iceland ), I have heard it at times on
JJY  ( 40 KHz ), the strongest one for me is on 48.800
KHz ( Puerto Rico ) always  there; booming strong. If I
remember right, I think I even heard it at 73.750  KHz
pretty strong too. I am curious if anyone might know
what type of  signal it is ?
Thanks for any replys: 73, Andy - KU4XR  


Hi Andy,
I think you mean the strong signal you are hearing is on 40.80KHz, not  
48.80KHz - that is from Puerto Rico, one of a number of U.S. Navy fleet  broadcasts 
on VLF below 60.00KHz.
 
The U.S. Navy and other ocean-going fleets use VLF broadcasts to  insure 
reception to vessels at sea and also to submarines because of the  VLFsignals 
ability to penetrate below the surface of seawater. 
 
The mode is called MSK which stands for Minimum Shift Keying but I am  not 
sure exactly what format they are transmitting in. The transmissions are  
encrypted so if you could properly decode them you would most likely just see  
strings of number or letter groups that have no meaning to someone without the  
code key.
 
The VLF transmissions are most likely used as backup nowadays to more  
sophisticated satellite comms but in an emergency they could be counted on to  get 
important messages thru to submarines below the surface if satellites were  
disrupted.
 
73 Todd WD4NGG



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