Ah, yes, the good old Collins receivers.
https://en.wikipedia.org/wiki/R-390ANote this:
Many of the R-390As that exist today are in the hands of vintage amateur radio collectors and amateur radio operators who contend that few modern solid state communications receivers can equal its performance.
My Son1 has what I believe is the original 390, which conists of a separate humongous 110VAC power supply plus the receiver itself. That receiver even has
mechanical IF filters in it, which were originally developed by Collns.
Typifies the expression "boat anchor" radio equipment.
Bearing in mind what I said about radio propagation being a complex matter, your receiving that station could be a result of "skip," directly receiving scattered reflections, or surface waves along the highly conductive sea water.
Also the fact that there was possibly a highly directional antenna involved aboard the Navy ship as well as excellent contact with the "ground," meaning the salty ocean.
Antenna engineers take a lot of effort to thoroughly ground (or "earth," in British parlance) the radio equipment.
And I don't mean connected to a cold water pipe. I mean with a radial pattern of conductors actually buried in the earth. (Amusing, but seriously, it is sometime recommended that in dry weather, the ham operator should go out and pee on his radial grounding system.)
In addition to all this, the Collins receivers were well-known for their sensitivity and selectivity.
Or it could have been a combination of all these factors.
It's tricky stuff.
Terry, 230RN
REF (Jes' 'cause it's interesting):
http://www.wa3key.com/filters.htmlContains a picture of the stacked, tuned iron slugs of a mechanical filter.
Mechanical filters are based on a little known property of ferrous and some other metals known as magnetostriction. That is, they shrink or change shape slightly under the influence of a magnetic field:
https://en.wikipedia.org/wiki/MagnetostrictionWith the correct shaping and stacking of pieces of magnetostrictive materials, a very highly selective electronic filter can be produced. Thus the Collins "mechanical filter."
The action is similar to that of a quartz crystal filter, which is based on the crystal's bending and warping under an electric field, but IIRC, shaping the iron elements is a lot cheaper and faster than grinding a quartz filter and has some other advantages.