[Lf] history question

[hal]

On the original uses of lf can anyone tell me if these facts are true?

1) It was the German Navy prior to 1940 who began using LF to
communicate with
the submarine fleet?   If so, what year was it that they began?

2) Radio Luxemburg was the first international LF broadcast station?  I
recall
reading that some British engineers were involved with its design and
construction.
Anyone know the year.  This was pre-WWII, in the late 1920's or early
1930's.

3). The frequency of Hertz's spark resonator?   Was it LF?

4). Marconi's first transmitters, did these operate on LF or higher up?
What about
the famous transatlantic (Europe to Canada) transmission?

5) How did NDB find themselves clustered around 200Khz and up?  When did
this start.
NDB began before WWII along short hop flight routes in the US and
elsewhere. Why LF and
why there?  Is there an international convention where this was first
recognized?

6)The first US Navy transmitter that used long wave operated from Ft
Meyer in Arlington VA (?)
Were other nations were also operating LF transmitters for their naval
forces?  Does anyone
know of a reference to early US Navy communications experiments?

--Hal