[ntp:questions] Any Spectracom hackers out there?

John Ackermann N8UR jra at febo.com
Sun Oct 24 14:28:13 UTC 2004


I'm planning to try some experimental mods on a Spectracom 8170 WWVB 
clock and wonder if anyone out there has done (or considered) something 
similar.  Please contact me off-list so we don't bore everyone else...

My hope is to remove the several millisecond jump and consequent long 
recovery time when the receiver momentarily loses lock, which seems to 
happen every couple of days.

The 8170 phase locks a 10MHz crystal to the WWVB signal, dividing that 
down to 1pps for the on-time signal.  It then decodes the WWVB timecode, 
and shifts (delays or advances) the 1pps in 100us steps in a slow PLL to 
stay on the mark.

My thought is to replace the phaselocked 10MHz signal with an external 
oscillator (in my case, an Rb standard that's monitored against LORAN-C) 
to avoid the bump that happens when the cheap 10MHz crystal in the 8170 
loses lock and free runs for a few minutes.

Spectracom had an option to automatically switch to an external 
reference when the WWVB signal was lost, but I'm wondering if it would 
work to use the external clock all the time, since the Rb is kept within 
a few parts in 10e-12 of LORAN (and is also checked against GPS every so 
often).

Just curious if anyone else has looked into this.

Thanks,

John N8UR
jra at febo.com



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