[tacgps] Re: [time-nuts] Any Spectracom hackers out there?

[Brooke Clarke]

Hi John:

Is the idea to be able to decode the WWVB time signal by using a known 
frequency?
Do you have docs on the 8170?

Have Fun,

Brooke Clarke, N6GCE

-- 
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
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John Ackermann N8UR wrote:

> 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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