On Tue, Jan 3, 2012 at 9:54 AM, wrote: > Do they still use ELF? I had been given to understand that they use laser= s from spacecraft these days, green blue lasers penetrate the water quite w= ell apparently, and the resultant data rate is much faster than ELF, and ha= s a potentially bidirectional path. It's been a little while since I did any work with UW comms (and if I had done anything more recent which changed anything I don't suppose I could discuss it freely on here!) but certainly until very recently VLF/ELF was what they were doing. I just can't see using lasers between spacecraft and subs being practical in terms of spacecraft location/availability, pointing accuracy, gain etc. I do know a bit about why you might not pick up the VLF/ELF signals easily, but that definitely comes under things I can't talk about. Chris --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .