[time-nuts] TrueTime XL-DC questions

[Robert DiRosario]

At a hamfest a few of weeks ago I got a TrueTime XL-DC, with antenna and 
feedline for $45. :-) With the antenna setup in my living room it works 
great, in good weather. It's the 1U version, with only the center LCD 
display. The IRIG-B output works. I found a manual at

https://web.archive.org/web/20161222211531/glacier.lbl.gov/gtp/DOM/Support/xl-dc-manual.pdf. 
There is also on at 
https://web.archive.org/web/20161226212915/https://ics-web.sns.ornl.gov/timing/151-652-893man.pdf, 
but it's newer than my unit. The manual shows the unit labeled as 
Symmetricom. with a large LCD for the time/date only and the small LCD. 
Mine is labeled TrueTime and has only the small LCD. The manuals do not 
have any information on the option cards. Is that documentation on the 
web anywhere?

I have two option cards. One is an NTP card, labeled NTL-XL 87-6003-XL, 
with an AUE Ethernet port.

The second card is labeled “HAVE QUICK II” 86-396-3 and has one of three 
BNC connectors installed. A scope shows that it puts out a low speed 
serial digital signal. Does anyone know what this card is for? The US 
military has a secure radio system named Have Quick, everything Google 
turns up is for that.

Can I upgrade this unit with one of these cards, to get 10 MHz output?

https://www.ebay.com/itm/Used-Truetime-XL-DC-GPS-Time-Frequency-Receiver-Module-Card-85-600-Rev-C/312792439289

It's made to go into the larger 2U version. If I remove the top bracket 
it will fit in my unit, but will it work?

Is the 10 MHz output a GPSDO?


On my unit Function 71 shows on the LCD display:


Osc Phase, I see numbers +/- in the range of e-9 to e-10. It updates at 2 Hz

Osc Offset, same as above but the scale is +/- e-10 to e-11, sometimes 
down to e-14. It also updates at 2 Hz

Osc Drift is of the order of 10e-9 per day. It updates at 2 Hz, or slower.

DAC is -17645, +/- 30 or so, and it doesn't update/change very often.

Respone Time 1.250E+01 seconds. It does not change, and the maual makes 
to mention of it.


Manual:

"Oscillator phase" is the instantaneous error between the XL-DC timing 
outputs and GPS.

"Oscillator offset" is the frequency offset or error with respect to the 
GPS frequency

"Oscillator drift" is the change in oscillator frequency per day.

"Oscillator DAC" is the signed 16 bit DAC control integer which sets the 
DAC output voltage to control

the internal or external oscillator.


On this list the next question is, how good is this? Looking at the 
manual and inside of the unit I think

it has just a TCXO.


I will use the 1 PPS output to drive a Shera board.

Thanks

Robert