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

Fri Mar 8 10:59:32 EST 2024

At least one thing works out when running AFSK. If xmt/rcv audio is mark
low, you will be OK for military USB (RF mark low) and also OK for ham LSB
(RF mark high).

Nick England K4NYW
www.navy-radio.com

On Fri, Mar 8, 2024 at 10:43 AM John Spigel <w1an.dxusa at gmail.com> wrote:

> And, for us today, adding to the permutation mix of possible settings
> you need to include along with AM/FM, USB and LSB.  With some mix of
> combinations, not necessarily the same, we can talk to each other. The
> Dovetron Tempest I'm playing with had an AFSK output which initially I
> set for Mark Low, Space High with normal operation LSB.  But on the net
> last Saturday I needed to copy in REV, because the other side of the QSO
> needed to go to REV to copy me and we are on USB! We could copy, but,
> unless told, what I think are correct settings are not! I could of
> course flip the Mark and Space with the front M/S frequency dials, but
> that would add to my confusion.  So in the interim I've added a switch
> on my Dovetron rear panel to flip High/Low for my loop generated Tx
> signal to give me that option and let others in the group copy and
> transmit "Normally" and for me to determine what is NORMAL. I'll
> probably also need to keep a cheat sheet!
> 73, John W1AN
>
>
> On 08-Mar-24 13:27, 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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