[time-nuts] I've been thinking about a GPS receiver experiment
aphid1 at comcast.net
Thu Oct 26 03:37:26 UTC 2017
Sorry, my mistake, change that to the former! I have used DACs that
were monotonic with decent results but prefer analog loops when the
time constants are short enough.
On 10/25/2017 5:46 PM, Bob Martin wrote:
> The holdover state is a DAC set to the last value of the analog
> control voltage that adjusts the oscillator frequency. Some designs
> use an analog control loop and switch the DAC into the control loop.
> Others use the DAC to set the control voltage at all times. This can
> result in a steps in the control voltage (output frequency).
> I've used both methods and prefer the latter.
> Bob M
> On 10/25/2017 5:30 PM, Mark Sims wrote:
>>> No, you set up an oscillator so that is why you have that problem.
>> I hooked the two rubidiums together just to see what would
>> happen. It pretty much did what I expected... chaos... the
>> time-nut equivalent of a naughty schoolboy putting a microphone up
>> to the speaker of the public address system. I't's a tough job,
>> but somebody gotta do it ;-)
>>> No, not really. The rubidium would be the real hold-over clock.
>> Symmetricom calls the disciplining state where it can't lock to
>> the 1PPS signal the "holdover" state. It's sort of like a GPSDO
>> holdover state. Their discipline firmware does let you set the
>> time constant and damping values. I tried a little playing around
>> with them, but never found any settings that worked consistently
>> well with the LEA-5T.
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