[Milsurplus] Underwater VLF reception (and old SSBNs)

[Mike Morrow]

>However, pre-nuclear submarines didn't patrol submerged. So receiving
>or transmitting while submerged would be an interesting phenomenon,
>but hardly of worthwhile practical use.

More than 30 years ago when I was OOD on a ballistic missile submarine,
maintenance of continuous reception of the appropriate VLF transmissions
was absolutely the *highest* priority of operations.  Any communication
loss figured *very* prominently in the CO's post-patrol report.  Without
appropriate communication, the rest of the SSBN package is useless.  (But,
SSBNs of the pre-Klintoon era did NOT require an *external* command link to
enable weapon deployment.  The boat carried everybody and everything needed
to deploy the RVs without outside facilitation.  But that's changed.) 

The heart of that system was the AN/BRR-3 receivers on board.  I'd like to
have an AN/BRR-3 as a significant cold war relic, but its 14 to 30 kHz
total range is not too useful for hobbyists.  The AN/WRR-3(*) was also carried,
and is IMHO the finest 14 to 600 kHz receiver ever to reach surplus.  It is much
more useful.  (I've got the AN/WRR-3B...such as was in naval use at least
into the early 1990s, and all vacuum tube.  Unfortunately, that interesting
maritime Morse band above 420 kHz is long gone today.)

The preferred SSBN VLF antenna system was a towed submerged bouy with an
automatic depth control system that maintained the bouy submerged but its
whip antenna projecting above the water surface.  But sometimes bouy depth
control failed, or the bouy flooded, or the bouy couldn't be retracted
into its storage place in the upper aft superstructure.  This resulted in
the need to cut the tow and abandon the bouy (very expensive to taxpayers!)

The backup was a bouyant wire that could be trailed out behind the sub's sail.

Another backup was a VLF "football" omni-loop that could be raised on a mast
from the top of the sub's sail.

SSN (fast attack) boats do not have a towed bouy antenna.

The characteristics of underwater VLF reception have been very well understood
and implemented for more than 50 years.

There were, of course, no VLF transmissions from the sub.  HF or UHF (including
satellite) transmission was possible, using masts raised from the sail (above the
water).  Most often the only transmissions during an entire patrol were those from
commercial marine VHF-FM handheld units used by the bridge watch officers to tugs
assisting undocking or docking at the beginning and end of the patrol.

There's no telling what is in use today.  Today's strategic nuclear forces are pretty
much forgotten entities, though I can think of a number of localities where the magic
wrought by a flight of MIRVs could change things for the better.

Mike / KK5F