[GreenKeys] Military Mark High to Mark Low change - FWIW

[Doug Jackson]

Surely it was done as a security measure. 🤔

On Sat, 9 Mar 2024, 1:15 am Duncan Brown, <duncanancy at earthlink.net> wrote:

> The decision as probably made by someone who had never operated RTTY/RATT !
>
> 73,
>
> Duncan
> K2OEQ
>
> On 08-Mar-24 08:27, John Vendely wrote:
> > Hey Nick,
> >
> > The reason for various military branches switching from MARK high to
> > MARK low is surely one of the world's great mysteries, on par with the
> > construction of the pyramids.  From an engineering perspective, the
> > choice is entirely arbitrary, but so far as I can see, prior to the
> > U.S. Army's introduction of the MD-522 in 1967, MARK high was the
> > convention.  So why change?  This must have been a bit confusing at
> > times for Army RATT operators, since their existing GRC-26 and GRC-46
> > equipment was MARK high...
> >
> > 73,
> >
> > John K9WT
> >
> > On 3/7/2024 1:16 PM, Nick England wrote:
> >> From a 1989 Coast Guard Manual -
> >>
> >> CV-3883/UG Converter Keyer AFSK Frequency Adjustment Information
> >> If you have ever aligned a CV-3883/UG Dovetron you probably noticed
> >> the absence of Navy and Coast Guard frequency shift information. Το
> >> complicate matters, prior to about 1972 the Navy's Normal mode of
> >> operation was wide shift RATT with the MARK tone HIGH and the SPACE
> >> tone LOW.
> >> The Navy made Reverse keying MARK tone LOW and SPACE tone HIGH the
> >> normal mode of operation in 1972 but stayed with wide shift. On
> >> existing signal conversion equipment radio operators would put the
> >> RATT converter in the REVERSE mode to correct the output logic of the
> >> received now MARK LOW signals.
> >> Technical manuals for older Navy equipment reflect the original Mark
> >> High Space Low convention e.g. the CV-2460/SGC. Manuals for newer
> >> equipment e.g. the AN/URA-17E reflect the Mark Low convention.
> >> The Coast Guard uses Space High Mark Low narrow shift keying as its
> >> normal mode of operation. Some old timers argue that this is REVERSE
> >> keying, but the bottom line is that Mark Low is the standard to which
> >> we align our CV-3883/UG in the Normal mode of operation.
> >>
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>
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