Thanks to AMRAD member Shannon Mishey for pointing out Throb. It might have some merit, perhaps with variation, for weak signal LF comms. A major downside is the need for a linear power amplifier. You can find out about it at <http://www.lsear.freeserve.co.uk/page3.html>. Frank -- Frank Gentges K0BRA, ex AK4R, W3FGL Check out our LF web page at <http://amrad.org/projects/lf>