NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Radio-quiet oceans and emergency navigation
From: Peter Monta
Date: 2013 Dec 9, 02:32 -0800
It would be interesting to see a shortwave spectrum from Tahiti. I suspect it would be littered with many weak carriers from all over the world.
Cheers,
Peter
From: Peter Monta
Date: 2013 Dec 9, 02:32 -0800
It might be quite a while before there really aren't enough signals for mid-ocean RDF. Broadcast-band AM signals can propagate for thousands of miles at night, and if we include shortwave AM or VSB, those can go tens of thousands of miles (indeed ionospheric skip propagation can result in the signal going multiple times around the earth).
Since there's a discrete carrier in these broadcasts, receiver sensitivity can be made very high by narrowing its bandwidth from the usual 5 kHz down to say 0.1 Hz or even smaller (limited only by the stability of the receiver and transmitter and signal path). Nothing heroic is required in the way of equipment: an all-coverage shortwave receiver and a laptop with sound input running a spectrum analyzer is more than sufficient.Cheers,
Peter
