On 3 Mar 2006 14:57:52 -0800, "purple_stars"
wrote:

most of the RDF equipment i've seen looks really old!

That's because it has been virtually obsolete for over 20 years, ever
since LORAN-C became widely available and affordable back in the early
'80s. Truth is, RDF was never all that accurate or reliable, it's
just that it was the only affordable electronic aide to navigation for
many years. I still have mine in the garage and I'm not expecting it
to move anytime soon. The best backup for GPS is another GPS, and
some spare batteries.