[GreenKeys] Wobbly FSK ?

[Nick England]

    Thanks - actually shipboard dual diversity reception was a
standard capability given the ubiquitous AN/URA-8A dual RTTY converter
with comparator. Ditto for earlier URA-6, URA-7 and later URA-17
dual-diversity converters. I imagine in practice this was usually
frequency diversity but could have been spatial with fore/aft
antennas.
     In addition to the 200 cps phase modulation capability being used
in the early outboard FSK modulators, I found the standard 1950's
shipboard MF/HF AM/CW/FSK  AN/URT-2, -3, -4 and AN/SRT-14, -15, -16
transmitters had it built in too. And so did the 1960's shipboard
LF/MF AM/CW/FSK AN/WRT-1 transmitter.
     So maybe wobbling turned out to be fairly useful. How much MF/HF
ship-to-ship RATT traffic was there? I know UHF relay to task force
ships was common. Man, I wish I knew someone who was responsible for
this stuff at BuShips back in the 1950's to talk with!

FWIW, this feature disappeared with the advent of SSB shipboard
transmitters - the 1960's AN/WRT-2 has an internal 425 cps oscillator
that alternately drives the USB and LSB modulators for mark and space
(ooh, that's weird!) - but with no extra wobbler. Then later
everything switched to AFSK (VFCT) and ISB I guess.

cheers,
Nick K4NYW
www.navy-radio.com


On Fri, Aug 19, 2011 at 11:01 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:
> Still more on this topic.  I've run across a paper in RCA Review,
> March 1946, by Peterson et al, "Observations and comparisons on
> radio telegraph signaling by frequency shift and on-off keying."
> As you might expect, FSK is a big win over make-and-break.  They also
> note in the summary "the use of superimposed 200 cycle phase modulation
> was not found to yield a gain on the FST system when space diversity is
> provided.  however some gain is indicated where a single receiver is used."
>  That would make it seem that wobby FSK might be advantageous
> for shore-to-ship transmission, since the ship can't very well use
> diversity reception; but would not be advantageous for transmission
> from a ship if the shore station has diversity antennas.
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