Re: [time-nuts] 1PPS for the beginner

Hi Bernd, One reference to 20us 1PPS pulse length is the ICD-GPS-060, see figure 3-2, page 3-3 (pdf page 19) https://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf Group - Are there other standard documents defining duty-cycle, voltage levels, rise times etc? MfG Björn > On 14 Aug

Re: [time-nuts] PPS pulse length (was: 1PPS for the beginner)

On Tue, Aug 14, 2018 at 10:34 PM Tom Van Baak wrote: > One version of this would be to make the pulse width 100 ns * (1+STOD), where > STOD (Seconds-Time-Of-Day) varies from 0 to 86399. So your pulse width > would vary from 100 ns to 864 ns = 8.64 ms. If 100 ns is too short use a >

Re: [time-nuts] Symmetricom (Datum/Microsemi) CS tubes after storage

After almost two more months things are looking much more promising. The ion pump current is down, and it's no longer throwing the pump overcurrent alarm. so I'm going to try and get it shipped home to Australia. Here's the status from just a few minutes ago:

Re: [time-nuts] PPS pulse length (was: 1PPS for the beginner)

> Arecibo did a kind of cute trick with their distributed 1PPS. The one > second pulses were of one length > (100 ns as I recall), but the 10 sec boundaries had the pulses be about > twice that length. One could carry > this scheme to considerable lengths as desired. Dana, One version of this

Re: [time-nuts] PPS pulse length

On 8/14/18 2:15 PM, Dana Whitlow wrote: Arecibo did a kind of cute trick with their distributed 1PPS. The one second pulses were of one length (100 ns as I recall), but the 10 sec boundaries had the pulses be about twice that length. One could carry this scheme to considerable lengths as

Re: [time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

On Tue, 14 Aug 2018 14:42:52 -0700 Wayne Holder wrote: > I'm not sure what you consider "low cost' but a 16 bit DAC like the > MAX5216BGUA+ > > goes for $3.40, quantity

Re: [time-nuts] Pressure related rubidium oscillator aging

What you say makes good sense, as He does not stick around very well- it would tend to diffuse out through the cell walls. I once spoke with a fellow involved in the deep sea diving business, and he claimed that vidicon cameras used in the deep habitats used to deteriorate in performance in a

Re: [time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

> Hene we would need a DAC resolution of 1e-4 or 14bit. That's already a DAC that has a price > tag, multiple times that of the TCXO. I'm not sure what you consider "low cost' but a 16 bit DAC like the MAX5216BGUA+

[time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

On Tue, 14 Aug 2018 13:56:40 -0700 ed breya wrote: > Perhaps what's needed is a clock that is reasonably stable, like a TCXO, > that can be dithered over some range and rate so that the sawtooths > never get stretched out far enough to become bridges. If the dithering > is in a predictable or

[time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

On Tue, 14 Aug 2018 11:05:17 -0400 Bob kb8tq wrote: > > Is there a need to make the math easier? > > This is what we have microprocessors for. > > There is *always* a need to make the math easier if I’m quickly typing up an > example. For proof I > reference the hundreds of posts in the

Re: [time-nuts] Pressure related rubidium oscillator aging

On Tue, 14 Aug 2018 14:23:56 -0500 Dana Whitlow wrote: > Does the Rb cell use He as a buffer gas? AFAIK most use a Ne/N mixture these days. I am not sure whether I have seen He used as buffer gas for Rb cells, but I do not think so. Other noble gases (Ar, Xe, ...) popped up a few times, though.

Re: [time-nuts] 1PPS for the beginner

On Tue, August 14, 2018 3:56 pm, ed breya wrote: > Then I wondered about what would happen if the > GPS receiver's internal clock, instead of > being from a drifty TCXO, was synchronized and "perfect," The Trimble Thunderbolt works that way. A very good GPDSO. You need access to the GPS

Re: [time-nuts] PPS pulse length (was: 1PPS for the beginner)

Arecibo did a kind of cute trick with their distributed 1PPS. The one second pulses were of one length (100 ns as I recall), but the 10 sec boundaries had the pulses be about twice that length. One could carry this scheme to considerable lengths as desired. Dana On Tue, Aug 14, 2018 at 4:00

Re: [time-nuts] Pressure related rubidium oscillator aging

On Tue, 14 Aug 2018 11:53:17 -0600 Skip Withrow wrote: > So far, I have been operating in the 10-50 Torr range and have seen a > very definite trend on aging with pressure. But there is much more > research to do. My big question is - what pressure related mechanism > might affect aging? I

[time-nuts] PPS pulse length (was: 1PPS for the beginner)

On Tue, 14 Aug 2018 20:52:50 +0200 "Bernd Neubig" wrote: > Is there any common practice for the duty cycle of the 1 PPS pulse? As short as the consumer can take. Because a long pulse means that you are wasting energy and heating up both the pulse generator and the consumer. As TvB wrote, it

[time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

On Tue, 14 Aug 2018 08:34:06 -0500 Dana Whitlow wrote: > I once read that the LO, at least, in some GPS receivers, was not even > crystal > controlled but was rather a ring oscillator based on a string of cascaded > logic inverters on the chip. This always sounded improbable to me, and i've >

Re: [time-nuts] 1PPS for the beginner

Bernd, Typically all you want is the leading edge. So a 10 or 20 us wide pulse is enough for most purposes. The duty cycle is essentially zero in this case. A noted exception is when the pulse is detected using vintage RS232 modem signal inputs, for example, when NTP uses DCD to catch a 1PPS.

Re: [time-nuts] 1PPS for the beginner

With a scope it is super easy to look at PPS pulses that are microsecond to a few milliseconds wide and tell you are triggering on the "leading edge". Harder to decide at 50% duty cycle especially if you think it might have been inverted along the way (almost all buffers are inverting). Of

Re: [time-nuts] Pressure related rubidium oscillator aging

Hi Aging in the short term tends to be dominated by equilibrium issues. Some of them can have “many months” sort of time constants . That makes any study like this pretty hard to do. Worst case is when a short term effect has the opposite sign from the long term. You go through a really flat

Re: [time-nuts] 1PPS for the beginner

> Is there a time-nuts FAQ? Hi Ron, We've considered that several times. There are problems. Also it's hard to beat the already superb NIST Time & Frequency FAQ / A-Z glossary. There's an index, or just start with A and read through several dozen webs pages until you get to Z:

Re: [time-nuts] 1PPS for the beginner

On 8/14/18 8:13 AM, Poul-Henning Kamp wrote: In message <20180814143354.ga29...@panix.com>, Ron Bean writes: Is there a time-nuts FAQ? Every so often somebody proposes a time-nuts wiki, then somebody tries to read the manual page for the mediawiki software and the idea dies again

[time-nuts] Pressure related rubidium oscillator aging

Hello Time-Nuts, For the past several months I have been investigating the change in aging rate of a rubidium oscillator with change in pressure. This has been done with an operating oscillator in a temperature controlled vacuum chamber. Obviously, the frequency changes (a lot) with pressure

Re: [time-nuts] 1PPS for the beginner

Thanks Bob and Azello. Now I understand the terminology and also better the mechanism for the sawtooth error. I once read that the LO, at least, in some GPS receivers, was not even crystal controlled but was rather a ring oscillator based on a string of cascaded logic inverters on the chip.

Re: [time-nuts] 1PPS for the beginner

In message , Dana Whitlow writes: > Could someone please define and explain the term 'hanging bridge' in this > context? Look first at this illustrative plot from Toms site: http://www.leapsecond.com/pages/m12/1phase8.gif The situation is the following: The gps receiver

Re: [time-nuts] 1PPS for the beginner

Hi A normal GPS module generates it’s outputs off of a free running internal clock. Generally this is a TCXO in a “timing” GPS ( = one that puts out a rational PPS). This is a bit counter intuitive, since you would *think* they phase lock the local source in the module. They don’t mainly

Re: [time-nuts] 1PPS for the beginner

For a definition of hanging bridge in the GPS receiver's context see: On Tue, Aug 14, 2018 at 2:58 PM jimlux wrote: > > On 8/14/18 12:29 AM, Mike Cook wrote: > > >> Le 14 août 2018 à 04:29, Chris Caudle a écrit : > >> > >> On Mon, August 13,

Re: [time-nuts] 1PPS for the beginner

Could someone please define and explain the term 'hanging bridge' in this context? Thanks, Dana On Tue, Aug 14, 2018 at 7:02 AM, Azelio Boriani wrote: > Hanging bridges out of a GPSDO's PPS? Interesting... time to try to > setup a measurement and see the relation between the GPS's PPS

Re: [time-nuts] 1PPS for the beginner

Hanging bridges out of a GPSDO's PPS? Interesting... time to try to setup a measurement and see the relation between the GPS's PPS hanging bridges and the corresponding DO's ones. On Tue, Aug 14, 2018 at 9:55 AM Mike Cook wrote: > > > > Le 14 août 2018 à 09:29, Mike Cook a écrit : > > > > Sorry

Re: [time-nuts] solar flares and time references Re: NIST

An interesting interaction between the near Earth CMEs and the geomagnetic field leads to some complex results also. Googling Carrington Event will give some interesting details. The geomagnetic and geoelectric field monitoring at observatories of CME interaction and associated earth

Re: [time-nuts] EFOS2 Maser acting up :(

Corby, When you write "I.F. Level", I assume you mean the 5.7KHz going to the PLL - or are you monitoring some other signal? Re LO; I would expect any issue with the LO would be directly observable on the output from the Maser - only an isolation amp in between. Have you measured the EFC on the

Re: [time-nuts] 1PPS for the beginner

> Le 14 août 2018 à 09:29, Mike Cook a écrit : > > Sorry about the previous blank mail. Finger jitter. > > > >> Le 14 août 2018 à 04:29, Chris Caudle a écrit : >> >> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote: >>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+

Re: [time-nuts] 1PPS for the beginner

In message , Mike Cook writes: > I don’t think that you are buying much with disciplining the PRS10 > with a GPSDO 1PPS. Do you have any TIC measurements in this config > to compare with a direct GPS 1PPS feed? There is a large footnote about "hanging bridges" here. If you feed the

Re: [time-nuts] 1PPS for the beginner

Sorry about the previous blank mail. Finger jitter. > Le 14 août 2018 à 04:29, Chris Caudle a écrit : > > On Mon, August 13, 2018 9:16 pm, Chris Burford wrote: >> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ OCXO >> that I am using to steer a PRS10 RFS. I'm a little

Re: [time-nuts] 1PPS for the beginner

> Le 14 août 2018 à 04:29, Chris Caudle a écrit : > > On Mon, August 13, 2018 9:16 pm, Chris Burford wrote: >> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ OCXO >> that I am using to steer a PRS10 RFS. I'm a little confused on where the >> 1PPS is coming from with respect