[Milsurplus] Naval History and LO radiation

[Don Davis]

John said:

Compare the DF as a search technique to a relatively early radar,
That means at extreme range it can search a 140 mi wide path.
That's a whole lot more than a DF system seems capable of, and this is a
very
early radar.

AFAIK, the only down side of using such a system is that it's an active
search,
rather than a passive one.


Don Replies:

So what?  How can one compare RADAR with DFing?  DF and RADAR are two
completely different things that have nothing to do with one another.  RADAR
is a search technique designed to locate objects due to reflection of the
RADAR signal.. DF is designed to locate a distant radio source and is an
intercept technique, not a search technique.  The reason the allies were
able to use DFing successfully (referred to as HF-DF) was due to the fact
that the Germans in command back home were control freaks and had to have
daily disposition, location, activity reports sent by HF.  Doenitz was
especially insistent on this.  This is an early example of successful
SIGINT, relying on an enemy's poor operational practices.  Successful DFing
was done at many ranges; close-in by sub chasers and destroyer escorts, and
by fixed stations thousands of miles away.  HF-DF doesn't have any distance
restriction per se (as opposed to RADAR which does have a specific distance
limit), but propagation effects certainly make it more/less useful depending
on specific conditions.  Couple this with ULTRA intercepts, controlled by
the British Navy, that gave the location and sailing plans for all of the
German subs, it's a wonder any were able to operate at all.  The Germans
kept up the daily HF transmissions until late in the war, and ULTRA was
uninterrupted until after the invasion of France by the allies.

Germans came up with a radar rx to alert them to closing allied planes using
early low freq (VHF) RADAR.  They could submerge and avoid becoming toast
(right away at least).  The literature is replete with rumors and stories
about DFing RX emissions, but there is nothing to suggest that this was in
fact done successfully or accounted for any of the known sub kills (or
convoy interceptions by the Germans).  If anyone believes this is not the
case, I would invoke the old "argument ender": ...name one ship that was
sunk by Rx emissions....  Probably a combination of plausible denial to
protect ULTRA, advertising by Scott and others, and ignorance of folks
around the periphery in the Navy.  Recall that RADAR was brand new and many
Navy folks didn't believe in it or use it in the early war.  Battle of Savo
Island disaster was a sad result of that.

I would refer to Samuel Eliot Morison's 16 volume set "History of US Naval
Operations in WWII" especially vols I, II, IX, X, and XI (mostly I & X),
Winston Churchill's 6 vol History of WWII (can't put my hands on it for
specific citations), F. W. Winterbotham's "The ULTRA Secret",  Peter
Padfield's  "War Beneath the Sea", and R. V. Jones' writings on WWII
technology history (can't find his book in my library this minute).  If you
read through all of that you get a very good idea of each and every convoy
interception, sub attack, and sub sinking in the Atlantic.  Mostly we had a
very good idea of where they would be from intelligence, lots of sub patrols
(not very effective on their own before the late RADARs), lots of good DFing
from the HF-DF sets (at sea and fixed locations), and lots of airborne
searches.

73s

Don  AD6PB
WWII Navy History Crank