[time-nuts] Determination of the placement of the first pps

Chris Albertson albertson.chris at gmail.com
Wed Jan 25 14:54:40 EST 2012

I'm sure people will figure out all these undocumented features.  But
there is a danger is using any of them because some day your Rb
oscillator will fail and you will need to replace it.  You can't count
on the replacement unit to have the same set of undocumented features.

I do intend to lock mine to a T-Bolt. but I'll phase lock the 10MHz
signals not the PPS.
I think I can send both 10MHz to the 74HCT9046 a uPwill read the
74HCT9046 and then send rs-232 commands to adjust the fe5680 to reduce
the phase or frequency error

The uP might also check the temperature of the FE5680 and keep a table
of DDS words vs. temperature and use this table for hold over when the
GPS is disconnected.  I don't know.  First steps first need to play
with 74HCT9046 and need to write fe5680 library for Arduino.

On Wed, Jan 25, 2012 at 11:19 AM, Magnus Danielson
<magnus at rubidium.dyndns.org> wrote:
> Hi Joe,
> On 01/25/2012 08:04 PM, J. L. Trantham wrote:
>> Magnus,
>> Thanks for the research.  Now that I have read your information, I am
>> going
>> to have to go back and 'measure' the PPS output on my unit.  I just
>> 'eyeballed' the '1 PPS' and it seemed close to 1 second.
> Good luck. Hopefully I put you onto a working solution.
>> It would be nice to find a serial command that would allow placing the 1
>> PPS
>> at any arbitrary point in phase to match GPS.
>> My impression of reading the posts about the FE-5680A is that the 1 PPS is
>> likely there, just not easily documented.
> Well, being lazy enough not to go into the lab and open up my 5680 I went
> hunting the web and it seems like there was more out there than we seems to
> have been piecing together.
> Seems like a bit of more systematic research needs to be done. There are
> obviously at least two basic models, one older with 50,255+ MHz oscillators
> and various add-on boards and secondly the 60 MHz + DDS variant.
> Reverse-engineering the schematics and functions has only partly been done,
> but I haven't seen any systematic schematic popping out of the work.
> There is already plenty of information available, but it is not coordinated
> and systematically done to the level that most aspects can be written down
> in a service type of document.
> Cheers,
> Magnus
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Chris Albertson
Redondo Beach, California

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