[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Here is a plot of the Thunderbolt cold starting with the "initial DAC voltage" setting set to the peak value of the initial spike (and not the 10.00 MHz setting). The upward spike when the unit starts tracking sats (it took around twice as long to start tracking sats) is gone, but the DAC

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi > On Sep 13, 2016, at 10:36 PM, Scott Stobbe wrote: > > Hi bob, thank you for the polite response regarding rise time, indeed I > would fully agree. > > The rise time I was referring to was the DAC efc value in the plot mark had > previously attached. He just

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi Scott, The x-axis is shown in the dark blue text to the right of the big time display - 60 minutes total, 5 minutes per division. Peter On 14 September 2016 at 03:52, Scott Stobbe wrote: > Pardon my lack of knowledge regarding Lady Heather, what is the

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Mark wrote: Okee dokeee... here it is. Not much difference. The initial step is smaller, but it still spikes. After that things are pretty much the same. After it cool down, I'm doing another run with the initial voltage set to the peak of the spike. Excellent! Many thanks,

[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Pardon my lack of knowledge regarding Lady Heather, what is the x-axis scale? I assumed the text line above the plot is the various y-axis scales. This is good data. Thanks On Tuesday, 13 September 2016, Mark Sims > wrote: >

[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi bob, thank you for the polite response regarding rise time, indeed I would fully agree. The rise time I was referring to was the DAC efc value in the plot mark had previously attached. He just included a second plot as well. It would appear the tbolt is doing something else aggressively before

[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Okee dokeee... here it is. Not much difference. The initial step is smaller, but it still spikes. After that things are pretty much the same. After it cool down, I'm doing another run with the initial voltage set to the peak of the spike. One slight difference was with the new

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi The rise time of the edge is not a good measure of the accuracy of the timing It simply is a way to look at how fast your gate can ramp a signal. If you do a long term comparison of the frequency vs time and the time error vs time you will see that a tight (small) damping keeps the time

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Bob, that is an excellent proof by contradiction. The reason I asked is on the plot Mark shared that first rising edge is pretty sharp for a system with a 500 s time constant. On Tuesday, 13 September 2016, Bob Camp wrote: > Hi > > The pps sync is done by resetting the counter

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi The pps sync is done by resetting the counter that generates the PPS. At a 1 ppm frequency offset, it could take 500,000 seconds to steer it in with the OCXO. It unlikely people would wait for over a week for the PPS to line up …. Bob > On Sep 13, 2016, at 5:58 PM, Scott Stobbe

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Interesting discussion about startup. At startup the phase error of the synthesized PPS is +- 0.5 s. Is this coarsely set to the nearest ocxo cycle once gps time is established (would make sense to do it this way), or is the half second recovered steering the ocxo? On Tuesday, 13 September 2016,

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Can anybody say more about the integrator term in the Tbolt? In the Arduino GPSDO I have, I use 1/TC/TC/damping and use damping = 2. I see Nick Sayer do the same but use damping 1.75. Simulations I have done in Excel seems to indicate that a damping in my sense of about 3 could be better to

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Mark wrote: I just ran a tbolt (which has been off for a couple of months) and logged the state for a couple of hours... and then remembered something about the initial DAC value setting that I had figured out long ago... it has little to nothing to do with oscillator disciplining.The

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

If you have a good antenna setup and a constant temperature environment: The way to get the lowest noise over short time periods on a TBolt is to set the TC setting as high as you can (typically 500 to 1000+), and set the Damping factor as fast as you can (typically 0.7 to 1). The reason is

[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

I just ran a tbolt (which has been off for a couple of months) and logged the state for a couple of hours... and then remembered something about the initial DAC value setting that I had figured out long ago... it has little to nothing to do with oscillator disciplining.The tbolt drives the

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Warren wrote: A damping setting in a Tbolt of greater than 2 is not a good idea. It is if one is only concerned about frequency stability and accuracy and wants the best performance that can be obtained at tau < about 10 seconds. And a TC setting of >1000 is not a good idea unless using

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi > On Sep 11, 2016, at 11:04 AM, Charles Steinmetz wrote: > > I wrote: > >>> Actually, for best results from a cold start, it is best to set the >>> initial DAC voltage to whatever voltage produces 10.0 MHz *when the >>> oven is cold*. > > Bob replied: >

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

I wrote: Actually, for best results from a cold start, it is best to set the initial DAC voltage to whatever voltage produces 10.0 MHz *when the oven is cold*. Bob replied: …… errr … that’s pretty far off :) DAC at 10 or 20 minutes is probably the target. No, DAC for

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

A cold oven freq is off by hundred's by Hz, Much much greater than the range of the Dac The TBolt does not start tuning until it's oven has warmed up. Setting anything in the Tbolt biased on cold start turn-on is counter productive. It takes days or weeks for it settle down. At initial turn-on

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Hi > On Sep 11, 2016, at 3:35 AM, Charles Steinmetz wrote: > > Mark wrote: > >> Here's a little info on Lady Heather's oscillator autotune function for the >> Thunderbolt GPSDO > > Thanks, Mark, that is very helpful. > > Accordingly, for people interested in best

Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Mark wrote: Here's a little info on Lady Heather's oscillator autotune function for the Thunderbolt GPSDO Thanks, Mark, that is very helpful. Accordingly, for people interested in best frequency accuracy and stability, I suggest (1) running autotune, then (2) manually setting damping to

[time-nuts] Lady Heather's Tbolt oscillator auto-tune function

Here's a little info on Lady Heather's oscillator autotune function for the Thunderbolt GPSDO: The autotune function tries to optimize the settings for the oscillator disciplining parameters, antenna signal mask angle, and the signal level amplitude mask beyond what the default setting (which