[time-nuts] Symmetricom TS2100-GPS - 1PPS has 10uS offset

Esa Heikkinen tn1ajb at nic.fi
Fri May 10 14:05:46 EDT 2013


I bought Symmetricom Tymserve TS2100-GPS some time ago. When comparing 
it's 1PPS with Thunderbolt they are not in sync:

Symmetricom seems to be always about 10 uSec ahead. If I turn of the 
power and then on again, it will be in sync very short moment after the 
tracking led is turned in. But then it will always roll itself at 10 
uSec ahead and lock there, when the locked led turns on.

It seems that it has somehow wrong GPS PPS offset or maybe it's 
folloring the 1PPS signal from it's internal GPS from the wrong edge 
(this is just my guess; Thunderbolt has 10 uSec long PPS signal, maybe 
the internal GPS as well?)

I understand that TS2100 is not as accurate PPS source as Thunderbolt. 
But it's manual claims that 1PPS accuracy should be 1 uS. So this is 
clearly out of spec. This is strange because the Symmetricom seems to be 
high quality product. Obviously not?

Is there any way to fix this by adjusting some offset with telnet etc? 
If not, maybe I try to invert the 1PPS from internal GPS. Or if someone 
knows how to use Thunderbolt as a time source, I could use that and 
remove the internal GPS...


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