[time-nuts] Fwd: HP5061B Ion Current

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html You bring up an interesting point. As the cesium is used up over the years, it forms a cesium frost which deposits on everything inside the tube. If it gets thick enough it conducts or can arc between frost grains. A charged

[time-nuts] HP5061B Ion Current

It looks like that there is about 10% hysteresis on the cesium trip off/on. That may not be enough to prevent cycling on and off. I may not have made it clear but instability in the +3,500 voltage makes a big difference in the threshold ion current required for activation. If it fades it can

Re: [time-nuts] PLL Digital Loop Filter

Hi Some quick hints: 1) You need a way to digitize the phase input with adequate resolution. If you have a 1 second period and want 1 ns, you need a way to digitize at a 1:1,000,000,000 sort of level. That’s in the 30 bit range so a simple ADC isn’t going to do it alone. 2) You need a way to

Re: [time-nuts] PLL Digital Loop Filter

Hi Slipped a factor of 1,000 on the DAC … sorry about that … Bob > On Mar 21, 2017, at 7:25 PM, James Peroulas wrote: > > Thanks for the hints and references everyone. I'll dig in and possibly come > back with some more questions. > > BR, > James >

Re: [time-nuts] WTB: GPSDO

So it seems the threat of replacement and a bunch of plugging and replugging into different computers has spurred my recalcitrant GPSDO back into life and it is now producing output again... This leaves me with the original problem of low sensitivity but at least I can solve that problem by using

Re: [time-nuts] Time Dilation tinkering

Hi Ummm … e …. it’s a gas cell standard. I’d bet there is a pressure effect. Bob > On Mar 21, 2017, at 7:01 PM, Scott McGrath wrote: > > Noted > > However CSAC not subject to barometric effects as Rb units are > > Content by Scott > Typos by Siri > >> On Mar 21,

Re: [time-nuts] Time Dilation tinkering

scmcgr...@gmail.com said: > However CSAC not subject to barometric effects as Rb units are Does anybody tried to measure CSAC vs pressure? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe,

Re: [time-nuts] Fwd: HP5061B Ion Current

That's some very nice work, Donald. Looking back, I have junked one or two Cs tubes that might have been usable if I'd thought through the problem of high ion pump current as you and KB7APQ seem to have done. Another good reason to raise the lockout threshold would be to cut down on the

Re: [time-nuts] PLL Digital Loop Filter

Thanks for the hints and references everyone. I'll dig in and possibly come back with some more questions. BR, James ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and

[time-nuts] Fwd: HP5061B Ion Current

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html Paul: I don't think that I made myself clear. This power supply is a rare example of HP engineering incompetence. The transformer is EASILY capable of 10 Watts out at 3500 V. Instead they made it where it can't even put out 100

Re: [time-nuts] Four hour cycle in GPS NMEA jitter

> https://goo.gl/photos/JZhBbFKFzkBAykti6 > Why would a GPS module produce jitter with a pattern like this? Trent, I must admit I have not seen such a four hour "spike" before in the NMEA latency, however a clue may be that the GPS ephemeris (broadcast by the SV's) orbit description is valid only

Re: [time-nuts] Time Dilation tinkering

Scott McGrath wrote: > Or perhaps use the Symmetricom CSAC ... Chris Albertson wrote: > Get a weather balloon. Or there might already be an amateur group that > launches these. Balloons can go much higher than your local mountains. You'll both be interested to hear that CSAC+balloon was

Re: [time-nuts] Time Dilation tinkering

Noted However CSAC not subject to barometric effects as Rb units are Content by Scott Typos by Siri > On Mar 21, 2017, at 4:18 PM, jimlux wrote: > >> On 3/21/17 12:51 PM, Scott McGrath wrote: >> Or perhaps use the Symmetricom CSAC ... >> >> Relatively expensive but

Re: [time-nuts] Four hour cycle in GPS NMEA jitter

HI > On Mar 21, 2017, at 4:52 PM, Trent Piepho wrote: > > Thanks to all who responded. Yes, I know PPS is the way get a more > accurate timestamps. That is the plan, but it takes more time to write > FPGA programs. The surprise is not that there is considerable

Re: [time-nuts] Time Dilation tinkering

On 3/21/17 1:40 PM, Michael Wouters wrote: These are less stable than a rubidium eg tau=10e-11@1000s and monthly ageing of 9e-10. The price of these has gone up too- they're now about US5000. Really? That's a big increase. I bought some last year (well, in December 2015) and they were

[time-nuts] Timelab file wanted

Hi Guys, Does anyone have a multi-day (at least 5 days) timelab file comparing the 1PPS from a GPSDO to a Cesium standard, with a run of the mill rooftop antenna using at least an HP 5370A quality TIC?  I'm running a 7 day test like this, and I'd like to have something to compare to.  If you

Re: [time-nuts] Time Dilation tinkering

These are less stable than a rubidium eg tau=10e-11@1000s and monthly ageing of 9e-10. The price of these has gone up too- they're now about US5000. Cheers Michael On Wed, 22 Mar 2017 at 7:03 am, Scott McGrath wrote: > Or perhaps use the Symmetricom CSAC ... > >

Re: [time-nuts] Time Dilation tinkering

On 3/21/17 12:51 PM, Scott McGrath wrote: Or perhaps use the Symmetricom CSAC ... Relatively expensive but might work The CSAC is 8E-12 AVAR at 1000 seconds, comparable to a Rb. See also http://tycho.usno.navy.mil/ptti/2011papers/Paper27.pdf which shows a bit better performance (3E-12 @

Re: [time-nuts] Time Dilation tinkering

Or perhaps use the Symmetricom CSAC ... Relatively expensive but might work > On Mar 21, 2017, at 8:08 AM, Attila Kinali wrote: > > On Tue, 21 Mar 2017 13:38:51 +1100 > Hugh Blemings wrote: > >> This got me to wondering if a Rubidium based standard might

Re: [time-nuts] PLL performance?

Hi Scott, That's a nice project. Combining quartz and pendulum like that is essentially how a GPSDO works. In your case, instead of a 10 MHz oscillator you have a 1 MHz oscillator and instead of 1PPS you have 1/2 PPS. Whether you use an analog loop or a digital loop there are dozens of

Re: [time-nuts] ADEV query Timelab and TICC

Look at ICD-GPS-060. 10V into 50ohm, sub 50ns risetime and 20us pulse lenght is specified in figure 3-2. --     Björn Sent from my smartphone. Original message From: Hal Murray Date: 21/03/2017 19:18 (GMT+01:00) To: Tom Van Baak

Re: [time-nuts] PLL Digital Loop Filter

Roland Best, "Phase Locked Loops". I see from Amazon that it is up the 6th edition. I think I have the 3rd edition. https://www.amazon.com/Phase-Locked-Loops-Simulation-Applications/dp/0071493751/ref=sr_1_1?ie=UTF8=1490121310=8-1=best+phase+locked+loops I took a PLL class at StorageTek a while

Re: [time-nuts] PLL Digital Loop Filter

On Tue, 21 Mar 2017 11:19:22 -0400 paul swed wrote: > Have to say a search for PLL book by Best generates lots of stuff. None of > it about PLLs. Better hint please? I think Lyons may be a bit better.

Re: [time-nuts] ADEV query Timelab and TICC

t...@leapsecond.com said: > The TAPR dividers tend not to have "this problem" because they output at > wimpy TTL/CMOS levels. Modern CMOS drivers have fast rise times. As long as the rise time is short relative to the cable length, it gets doubled if the end of the cable is an open circuit.

[time-nuts] HP5061B Ion Current

If you cannot get the ion current below 50ua or so after a week at 5kV then you are out of luck. Most likely you have resistive deposits on the ion pump insulator. If you can get the tube to give a decent SN at those levels then you can run with the alarm circuit bypassed. I have run tubes a

Re: [time-nuts] PLL Digital Loop Filter

Have to say a search for PLL book by Best generates lots of stuff. None of it about PLLs. Better hint please? I think Lyons may be a bit better. Regards Paul WB8TSL On Tue, Mar 21, 2017 at 7:39 AM, Attila Kinali wrote: > On Mon, 20 Mar 2017 21:32:28 -0700 > James Peroulas

Re: [time-nuts] Time Dilation tinkering

Get a weather balloon. Or there might already be an amateur group that launches these. Balloons can go much higher than your local mountains. You al ill want to build an environmental chamber for the Rb clock. The chamber is heated and pressurized. Even for the maintain top experiment you will

Re: [time-nuts] PLL Digital Loop Filter

it is tempting to use digital loop filter for PLL if a very low bandwidth is required, but with the large time constant is a problem ; the VCO will change it's frequency despite the tuning voltage remains constant and that is not so simple to model. 73 KJ6UHN Alex On 3/21/2017 4:39 AM,

Re: [time-nuts] PLL performance?

To get your loop to lock and keep phase noise down the loop filter would need a bandwidth of .05 Hz or less. That would mean long lock times. Very long lock times.  Engineering is the art of making what you want from what you can get at a profit. I like Polywell Fusion. On Tuesday,

Re: [time-nuts] ADEV query Timelab and TICC

I know the the open load output of some instrument is 10Vpp and I think this is right because if we want to connect this output on a 50Ohm line is correct to close the cable with the proper load impedance. I have found this level also on some trak System equipment. All my test are

Re: [time-nuts] TS2100: Which OCXO's work?

Hi > On Mar 21, 2017, at 1:37 AM, Bruce Lane wrote: > > Fellow time-tickers, > > My thanks to Greg for getting back to me (and apologies for the spam > filter bounce) but, apparently, MTI 240 OCXO's have become unobtanium. > > With this in mind: What

Re: [time-nuts] Time Dilation tinkering

On Tue, 21 Mar 2017 13:38:51 +1100 Hugh Blemings wrote: > This got me to wondering if a Rubidium based standard might do the trick > - the Efratom SLCR-101s seem readily available for ~USD$200 mark. As TvB wrote, a single one will not do the trick. You will need a stability

Re: [time-nuts] Time Dilation tinkering

H > On Mar 21, 2017, at 4:58 AM, Tom Van Baak wrote: > > Hi Hugh, > >> If I do the math correctly that's about 14ns difference per 24h the >> clocks are separated by that altitude. [1] > > That's correct. For your 1500m elevation gain, the gravitational redshift, > the

Re: [time-nuts] PLL performance?

Moin, On Mon, 20 Mar 2017 21:07:03 -0400 David Scott Coburn wrote: > I have built and tested a PLL circuit that will be used to generate a 1 MHz > signal locked to a 0.5 HZ signal from a pendulum. (Details available upon > request.) [...] > I tested this by feeding the

Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

Hi > On Mar 21, 2017, at 1:07 AM, Chris Albertson > wrote: > > I built one of these using a PWM DAC also. The design was posted to this > list so I can't take credit for the idea. But we used two PWM output > pins. The PWM provides more voltage range than is

Re: [time-nuts] PLL Digital Loop Filter

On Mon, 20 Mar 2017 21:32:28 -0700 James Peroulas wrote: > I'm trying to understand how to design and analyze the loop filters in a > digital PLL. Specifically, because of digital processing delays, the phase > offset measured at time t will only produce a change on the VCXO

Re: [time-nuts] PLL performance?

Andy, Bill, et al. Attached is a GIF version of Scott's (unreadable?) histogram-utcday21613x.pdf file. /tvb - Original Message - From: "Andy" To: "Discussion of precise time and frequency measurement" Sent: Tuesday, March 21, 2017 12:23 AM

Re: [time-nuts] Time Dilation tinkering

Hi Hugh, > If I do the math correctly that's about 14ns difference per 24h the > clocks are separated by that altitude. [1] That's correct. For your 1500m elevation gain, the gravitational redshift, the df/f frequency change, will be about 1.6e-13. To be able to measure with any confidence

Re: [time-nuts] PLL performance?

Second file successfully opened in Irfanview. Three other PDF readers, including Adobe, could not open it. Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow

[time-nuts] TS2100: Which OCXO's work?

Fellow time-tickers, My thanks to Greg for getting back to me (and apologies for the spam filter bounce) but, apparently, MTI 240 OCXO's have become unobtanium. With this in mind: What other OCXO's are compatible with the Symmetricom TS2100? My understanding is whatever I choose

Re: [time-nuts] PLL Digital Loop Filter

In message , James Peroulas writes: >I've found plenty of texts describing analog loop filters. Are there any >recommendations for digital loop filter PLL design? This may help:

Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

I built one of these using a PWM DAC also. The design was posted to this list so I can't take credit for the idea. But we used two PWM output pins. The PWM provides more voltage range than is needed by the OXO's EFC. To the output was scaled by a voltage divider. This also scaled down thew

Re: [time-nuts] Four hour cycle in GPS NMEA jitter

Wow. 350 nS. I had not been following this for the last few years. It seems the ARM is a simply CPU with much more predictable interrupts timing. One might ask way you'd need such good internal timing. What got me into this years ago was scientific data acquisition. I wanted to time