Re: [time-nuts] Next upgrade

Hi The “gotcha” with compensated devices is that there can be interesting breakpoints or decoupling to the sensor. Those show up more if the compensation is working very hard to get the job done. Put another way - if you start at 1x10^-9/C and compensate to 1x10^-11/C that is very different

[time-nuts] Next upgrade

BTW, that is the temp sensitivity of the X72 rubidiums that I have tested... -- Your OCXO may be happy at 1x10^-11 / C ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] Next upgrade

Hi If you only run over 10% of the EFC range, you only gain 3 bits. If the objective is in the 22 bit vicinity, (maybe 20 maybe 22 …) you really don’t get enough bits at a 10% span. From a lot of years of playing with control loops, if you need 20 *good* bits, you better have a few more than

Re: [time-nuts] Next upgrade

As I said in my original post from our point of view there are only two reasons for a Rb time and 16 bits will do the job. I would not do an OCXO with less than 22 bits if analog at all. Bert Kehren In a message dated 11/26/2017 8:56:51 A.M. Eastern Standard Time, opronnin...@gmail.com

Re: [time-nuts] Next upgrade

We tried coarse and fine using a LTC 24 bit ADC for characterization but test time is prohibitive and all the data has to be stored, or do it dynamically like Tbolt does, I suspect SRS does something like that on the OCXO they can afford it since it looks like the do that through out the

Re: [time-nuts] Next upgrade

...and what about shrinking the 16bit over the fraction of the EFC range that, for example, the OCXO will be using for the next 5 years? 16bit over 10V are as 20 (a little less, OK) over 1V, if I can use my 16bit over 1V for the next 5 years, when the DAC will be near full scale I can "trim" the

Re: [time-nuts] Next upgrade

Hi If you sum two DAC’s without any sort of feedback, you get problems when the “coarse” dac is changed. You have no way to know the step size of the coarse dac to (say) 20 bit precision. As an example : If you are after 20 “good” bits, you might overlap them at the 10 bit point on the coarse

Re: [time-nuts] Next upgrade

Is summing a "fine tune" 16bit DAC and a "coarse tune" 16bit (or less) DAC with an op-amp not good enough? On Sun, Nov 26, 2017 at 5:53 PM, Bob kb8tq wrote: > Hi > > Each time I’ve tried the method in the app note, there has been a tone in the > output > spectrum at the sample

Re: [time-nuts] Next upgrade

Hi Each time I’ve tried the method in the app note, there has been a tone in the output spectrum at the sample rate of the ADC. I’ve never found a way to do the grounding that eliminates it. The tone is large enough to show up as a spur on a “typical” OCXO when it goes into the EFC port.

Re: [time-nuts] Next upgrade

I guess everyone has seen this, but Linear has a nice appnote «A Standards Lab Grade 20-Bit DAC with 0.1ppm/°C Drift» http://cds.linear.com/docs/en/application-note/an86f.pdf Ole > 26. nov. 2017 kl. 13:50 skrev Magnus Danielson : > > Hi > >> On 11/26/2017 02:26

Re: [time-nuts] Next upgrade

Hi On 11/26/2017 02:26 PM, Attila Kinali wrote: Though, if you have a decent 16bit DAC and want to get to 18bit, that's fairly simple using delta-sigma modulation... if you can live with a low pass fillter after the DAC. But the DNL will be the limiting factor here (unless you use some special

Re: [time-nuts] Next upgrade

On Thu, 23 Nov 2017 13:18:35 -0500 Bert Kehren via time-nuts wrote: > There was recently discussion of the use of the LTC1655 which > is still my # 1 choice. What was not mentioned on the 1650 is that in needs > a external reference discontinued and double ling the cost.

Re: [time-nuts] Next upgrade

A few comments I forgot. Most Rb's can use a clean up loop, we are experimenting with Wenzel's 600 second loop recently posted here. Exceptions are the HP 5065 the optical unit is the source of the performance, Corby experimented with different OCXO, performance remained the same. Loop time

Re: [time-nuts] Next upgrade

The Next upgrade has touched several subjects we deal with on a dayle basis. Allow mw to add my thoughts. First we are time nuts trying within our limits to advance time and frequency generation and measurement with affordable resources. We are at least a factor four orders of magnitude

Re: [time-nuts] Next upgrade

Hi Yes, the “has no GPS” box becomes the active device in a REF0 / REF1 pair. If a survey is involved, it can take a *long* time for things to sort out. Bob > On Nov 23, 2017, at 7:22 AM, Adrian Godwin wrote: > > Turns out is does work - Initially, when I linked them,

Re: [time-nuts] Next upgrade

Turns out is does work - Initially, when I linked them, both boxes had the standby light go out and the unmodified ref-0 (with no GPS receiver) showed Fault and No GPS. So I assumed there was some problem that might be causing them to conflict over the interface, and unplugged it. I've tried it

Re: [time-nuts] Next upgrade

I once did make a token attempt at tweaking the disciplining parameters in that SRS-10, but seemed to be getting nowhere and gave up on the effort. Dana On Wed, Nov 22, 2017 at 8:12 PM, Mark Sims wrote: > The PRS-10 does have disciplining parameters that you can tweak.

Re: [time-nuts] Next upgrade

Based on all the input I think I am going to just save up my mad money for a Cesium and be done with it. (Doubt I’ll ever be “done with it”). > On Nov 22, 2017, at 6:12 PM, Mark Sims wrote: > > The PRS-10 does have disciplining parameters that you can tweak. But the >

[time-nuts] Next upgrade

The PRS-10 does have disciplining parameters that you can tweak. But the documentation is rather spotty on how to go about choosing good values. Also, I doubt that putting a Rb in an OCXO Lucent box would work well. Rb loop parameters (like time constant) are rather different for the two

Re: [time-nuts] Next upgrade

For the most part the SRS-10 is a nice choice, although I'd always be wary of buying a used one. My only real beefs are that the tuning granularity is rather coarse, about 2E-12, and the disciplining loop seems to be a bit aggressive so that the poor oscillator gets jerked around quite a bit by

Re: [time-nuts] Next upgrade

Adrian, when you stated it didn’t work, what were the results? I had mine running in HA mode, if you can call it that, because only one has a GPS. Actually now that I think about it, the separate but modified REF0 and modified REF1, assuming separate power and antennas, is probably closer to

Re: [time-nuts] Next upgrade

Yes, I cross-connected the pins, but I didn't cut any short. On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq wrote: > Hi > > I have run a number of the REF0 / REF1 combos. They all seem to work fine. > The standard cable has some odd short pins on it. If you are not hot > plugging

Re: [time-nuts] Next upgrade

Hi I have run a number of the REF0 / REF1 combos. They all seem to work fine. The standard cable has some odd short pins on it. If you are not hot plugging the cable I don’t think they matter at all. If anything, the system is more reliable with a normal length pin on the connector. Bob > On

Re: [time-nuts] Next upgrade

The 15pin cable has to be cross-connected. Maybe that is your problem? The pin connections were posted not that long ago. It is like 1-15; 2-14; 3-13; 4-12; 5-11; 6-10; 7-9; 8-8; 9-7; 10-6;11-5; etc. > On Nov 22, 2017, at 3:08 PM, Adrian Godwin wrote: > > I've got

Re: [time-nuts] Next upgrade

I've got several of the Ref 0 boxes but none of the Ref 1. I've added an Oncore GPS receiver to one of them as per Peter Garde's notes and it works well. But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1 configuration. Not that I need an HA reference but just for interest. I've

Re: [time-nuts] Next upgrade

Hi > On Nov 22, 2017, at 5:16 PM, Jerry Hancock wrote: > > Three questions: > > 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with both > supplying 10Mhz and 1PPS, is there a way to combine the outputs or some other > technique to improve the short

[time-nuts] Next upgrade

Three questions: 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with both supplying 10Mhz and 1PPS, is there a way to combine the outputs or some other technique to improve the short and/or long term performance? 2) I’ve become interested in Rubidium Disciplined Oscillators