NavList:

Frank,

You jogged another memory with that interesting analysis of early tube radios. Another joy of Pre GPS marine radio was the RDF.  

I grew up sailing with my father before GPS. We somewhat later on got first real electronic nav toy with a Loran C the size of an old picture tube TV. Before that I remember he specifically had purchased an old clunky looking but functional RDF. I also remember playing with time signals and world broadcasts on an ancient giant zenith tube radio "wave magnet" that at my young age felt like you were picking up a small car. 

As I grew, he taught me to triangulate known station transmissions with an RDF and verify a DR position, or run down an RDF bearing to a known point.

I remember  an old RDF I think from WW2 era with a big ring on top and later on the bendix 555.  I kick myself for not saving mine as a curio. I had an old Bendix that I let go when moving 15 years ago...it still worked.

From his USCG Officer days (Early 1960's), he related to me a rescue of a disabled vessel in storm off Hattaras by the large tug Chilula. He stated the rescue was done entirely (along with some amazing luck) by running down a fading RDF signal as the batteries failed on the powerless vessel until finally found by searchlights. I think that experience, was what caused him to carry it sailing.

The 555 guts were I recall an early transistor version.

Not very celestial, but still a very handy tool.

MC