Trak 6460 Multiple Time Scale Generator

The 6460 is a wonderful time display; one of the few that is capable of displaying more than one time scale. After entering the fixed offsets among the scales the 6460 can display time as either UTC, TAI, MJD, or GPS. Commands can be entered via the front keypad or sent over GPIB. Below is a photo of a Trak 6490 micro stepper driving a Trak 6460 multiple time scale display.

Keypad / GPIB commands

Time Display Commands

Command	Syntax	Description
1C	1C <enter>	Display UTC
2C	2C <enter>	Display TAI
3C	3C <enter>	Display MJD
4C	4C <enter>	Display Omega
5C	5C <enter>	Display Sidereal
6C	6C <enter>	Display GPS

Time Set Commands

Command	Syntax	Description
0A	0Ayymmdd <enter>	Set UTC date
1A	1Ahhmmss <enter>	Set UTC time

Time Scale Offset Commands

Command	Syntax	Description
2B	2Bss <enter>	Set UTC-TAI offset (seconds)
4B	4Bss <enter>	Set Omega offset (seconds)
6B	6Bss <enter>	Set GPS offset (seconds)

5B	5Bdddd <enter>	Set DUT1 (UT1-UTC) positive offset
8B	8Bdddd <enter>	Set DUT1 (UT1-UTC) negative offset
7B	7Bddddd <enter>	Set local sidereal offset (positive)
9B	9Bddddd <enter>	Set local sidereal offset (negative)

1 PPS Synchronization Commands

Command	Syntax	Description
4A	4Addddddd <enter>	Advance 1 PPS by ddd ddd.d us
5A	5Addddddd <enter>	Retard 1 PPS by ddd ddd.d us
8A	8A <enter>	Arm external sync

Other Commands

Command	Syntax	Description
2A	2Adddddd <enter>	Insert leap second in ddd ddd seconds
3A	3A <enter>	Insert leap second immediately
9A	9A <enter>	Lock input
	pppp <enter>	Unlock input (password)

Sample display formats

UTC mode shows MJD (Modified Julian Day), day of year, hours:minutes:seconds.

TAI mode shows hours:minutes:seconds only.

MJD mode shows MJD and fractional MJD, hours:minutes:seconds.

Omega mode (now obsolete) shows MJD, day of year, hours:minutes:seconds.

SID mode (sidereal time) is not implemented on Trak 6460 or 6460A.

GPS mode shows day of year, week number (less 1000), day of week, total seconds (ss ss ss) since start of week (0h Sunday).

Notes

The standard Trak 6460 has a serious Y2K bug that prevents the clock from displaying the correct MJD after 31 Dec 1999. But by entering the year 36 instead of 00 you can trick it into displaying the correct MJD during the year 2000. However on and after 1 Jan 2001 there is no work-around. Trak Microwave used to have an EPROM fix for this bug on their web site but no more. The above 6460 has the new EPROM's installed. You can burn your own: 2716.bin and 2732.bin.
When Trak Microwave took over the 6460 product from TST (Time Systems Technology) they renamed it the 6460A. Other than the name there are no differences between the 6460 and the 6460A.
The sidereal time display was never implemented correctly on the 6460. It's not easy generating a display when the sidereal day is 23:56:04.09 long instead of 24 hours. Rather than disabling the feature the manual just states it is not supported.
The "user interface" to change the display using the keypad is awkward.
There's no volume control on the 1 PPS beep but if you cover the hole with tape it will be much quieter.
In my lab I currently run the main frequency standard (H-maser) into the 6490 and the steered output of the phase micro stepper goes into the 6460 to produce my UTC(tvb) time scale.

See also Live TAI, UTC, GPS clocks.
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