Re: [time-nuts] WWVB SDR discussion

[Mark Haun]

No more so than for a GPSDO using a microcontroller.  In this case, the
MCU would steer an external oscillator using an appropriately long time
constant, based on a phase tracking loop.  In my tentative block
diagram, the oscillator is a cheap 26 MHz OCXO which supplies the MCU
clock and (as a byproduct) the internal ADC sample rate.  The basic plan
for an STM32L4 was something like

26 MHz clock input from OCXO
78 MHz MCU clock (x3 via internal PLL)
3.12 MHz ADC sample rate (78 MHz / 25)
13x downsample to 240 kHz using DFSDM block (hardware CIC)
sign flip and deinterleave into I and Q channels (I, Q, -I, -Q, ...)
downsample again, to ~ 10 Hz or so; do SDR stuff at this rate
carrier tracking loop runs back outside the MCU to the OCXO control
input, via PWM DAC

With care, the internal ADC gives you about 11 good bits at the high
sampling rate.  Assuming white noise (questionable I suppose), this
yields something like 18 noise-free bits at the low rate where the phase
tracking and decoding happens.

Prerequisite is an analog input centered around 60 kHz with less than
3.6Vp-p amplitude.  There are no particular bandwidth requirements
(Nyquist is 1.5 MHz!) as long as it is narrow enough to avoid clipping
from strong interfering signals.  I am having a hard time with this
part, unfortunately.  My tuned loop seems still too broadband, even
after a couple more poles of op-amp filter.  I have a bunch of 60-kHz
tuning-fork crystals and wanted to try a crystal filter like the "pros"
do in cheap consumer clocks, but I can't figure out a circuit to do this
(weak on analog).  So if anyone wants to tackle that and send me a
working design, I'm happy to do the easy stuff, i.e. the DSP/SDR parts ;)

Mark

On 10-Aug-20 11:45 AM, paul swed wrote:
> Hello to the group.
> Have been looking forward to seeing how the STM32 SDR project might be
> going.
> SDR is a weak spot for me. So been reading. And believe the answer is that
> a SDR solution may work for AM code and even BPSK code to an extent. But
> doesn't the sampling destroy the quality of the incoming signal for
> establishing a locked reference?
> Regards
> Paul
> WB8TSL
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] WWVB SDR discussion

[Bob kb8tq]

Hi

As long as you sample “fast enough”, you can recover phase. Indeed, even if
you sub-sample (sample to slow), you can still get phase back with a few 
relatively minor constraints. Since one of those is “don’t sub sample at exactly
a fraction of the carrier”, a sub-sample “locked” receiver would be a challenge.

Bob

> On Aug 10, 2020, at 2:45 PM, paul swed  wrote:
> 
> Hello to the group.
> Have been looking forward to seeing how the STM32 SDR project might be
> going.
> SDR is a weak spot for me. So been reading. And believe the answer is that
> a SDR solution may work for AM code and even BPSK code to an extent. But
> doesn't the sampling destroy the quality of the incoming signal for
> establishing a locked reference?
> Regards
> Paul
> WB8TSL
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] WWVB SDR discussion

[jimlux]

On 8/10/20 11:45 AM, paul swed wrote:

Hello to the group.
Have been looking forward to seeing how the STM32 SDR project might be
going.
SDR is a weak spot for me. So been reading. And believe the answer is that
a SDR solution may work for AM code and even BPSK code to an extent. But
doesn't the sampling destroy the quality of the incoming signal for
establishing a locked reference?



Not really.  Consider you want to know the phase of a sinewave, and 
you're sampling at 3.5321 samples/cycle (i.e. it doesn't have to be 
integer samples/cycle).  You can solve for the phase of the sinewave to 
any level of precision, limited essentially by the SNR of the samples 
(including any quantization effects).



You can do this repeatedly - and implement all you need in terms of a 
phase locked loop - entirely in the digital domain.


As it happens, some things are *easier* if you, for instance sample at 4 
times the frequency of the input signal - various clock rate noises 
alias to places that are not near the input signal.


So, sample with enough bits, digitally filter, run your PLL, and you can 
conceivably steer your processor's VCXO to be in a fixed frequency 
relationship with the input.(and maybe phase).



This is essentially what we do with modern deep space transponders - we 
digitize the received uplink signal (actually, at the IF), run that 
through a PLL tracking loop using the frequency error term to drive a 
DDS which generates the downlink signal. So we can keep the transmit 
frequency exactly at 880/749*receive frequency (For X-band, anyway).


There is some arithmetic involved to make sure that all the ratios come 
out right - and some design involved to make sure that errors (i.e. 
noise on the reference oscillator, which is fixed frequency) cancel 
appropriately.


The previous generation of transponders did a quasi digital PLL - the IF 
was digitized and processed to generate an error signal, which was then 
used to push the VCTCXO around - so the reference frequency was always a 
fixed fraction of the receive frequency (usually around 78-80MHz, for 
historical reasons). Then the transmit side just multiplied the 
oscillator up.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] WWVB SDR discussion

[paul swed]

Hello to the group.
Have been looking forward to seeing how the STM32 SDR project might be
going.
SDR is a weak spot for me. So been reading. And believe the answer is that
a SDR solution may work for AM code and even BPSK code to an extent. But
doesn't the sampling destroy the quality of the incoming signal for
establishing a locked reference?
Regards
Paul
WB8TSL
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Satelles PNT from Iridium satellites

[ew via time-nuts]

Allow me to clarify my GPS involvement. In 1973 TI moved me from Houston to 
Dallas to be part of the start up of calculators. This was followed by Marine 
projects since our chairman was an avid sailor. While working on Loran C my 
boss walked in one day and told me that at a staff meeting he had volunteered 
me to write the GPS proposals. It took me three days to convince him that this 
was not just sitting down and writing a proposal. It took over a month to get a 
team together of experts with at least order of magnitude more skills than me. 
I spend most my time on Pert Charts and reviews. Some coordination with 
Semiconductor on C and P code chips and SBP9900 bipolar 16 bit microprocessor. 
Cost calculation, lost our shirt on underestimating software development a 
first of this magnitude in TI Equipment Group (Military). We bid on two, did 
win both and I was given the choice which one. I picked Manpack. More top notch 
experts where added. Continued with typical program management. Do not recall 
any innovating technical contributions beside packaging. Bert Kehren
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Symmetricom X72

[paul swed]

The lamp oscillator should not have an affect. It just excites the lamp. I
did see in you picture some very complicated FPGA class chips. I would
expect the photocell/diode to hit an opamp. Though maybe thats in the FPGA.
On the face of the lamp when off and shining a light do you see a black
film? Not uncomment for the rubidium to plate onto the glass and
essentially dim the emitted light. It can be recovered if that is the case.
Regards
Paul.

On Mon, Aug 10, 2020 at 12:40 PM Germán Herrera 
wrote:

> Hi Paul,
>
> First of all, thank you for your advice.
>
> I did try with the cover on, and also with the magnetic shield on (which
> consists of about three sheets of mu metal wrapped around the resonator
> cavity over and below the board (you can see the slits on the bigger
> board, on the pictures).
>
> I've had mixed results, with the unit warmed up but without the cover, I
> had the opportunity to have it locked for quite some time (about 8
> hours) before powering it off again. Other times it doesn't lock. Other
> times where the unit starts cold, after a couple of minutes locks for a
> short (~30s) time and gets back to sweeping frequency (unlocked state).
> I've seen that happen on an Efratom FRK with a defective resonator
> thermistor, that's why my main suspect is the temperature.
>
> I still have pending to attach the scope to the photodector amplifier to
> check if I see the modulation signal. After that I think it all goes
> digital so there's nothing much I can do. I did try varying the lamp
> oscillator frequency but didn't notice any effect (kind of a long shot
> since I don't know the right frequency), so I left it as it originally
> was.
>
> Kind regards!
>
> ---
> Germán Herrera
> Responsable IT
> Ingeniería
> SES Sistemas Electrónicos S.A.| Espinosa 1045 (C1405AMM) | Buenos Aires
> | Argentina
> W: +54 11 54538426 | Email: g.herr...@ses.com.ar
>
> On 2020-08-10 10:21, paul swed wrote:
> > German have you tried with the cover back on?
> > The external light in your picture could be affecting the system.
> > The color of the RB lamp looks about right and its nice and bright.
> > Also most Rbs I have worked on tend to insulate the various ovens and
> > such.
> > Temperature matters.
> > Regards
> > Paul
> >
> > On Mon, Aug 10, 2020 at 9:15 AM Germán Herrera 
> > wrote:
> >
> >> Hi everyone
> >>
> >> This is my first post on the list, tought I've been subscribed for
> >> some
> >> time.
> >> I'm in the process of troubleshooting an X72 which recently started to
> >> be unable to acquire lock. I've searched online for pics of this
> >> standard and wasn't unable to find anything, so i took some nice
> >> pictures which I'd like to share with you:
> >>
> >>
> >>
> https://drive.google.com/drive/folders/1HN8dms5CxPwUjdckEux2fOVTF5IoaI5u?usp=sharing
> >>
> >> After disassembling it I found that an optical filter which is
> >> supposed
> >> to be glued to the light path of the lamp was loose inside the unit. I
> >> attached it again but the issue persisted.
> >>
> >> If anyone is able any information about the thing (such as lamp
> >> working
> >> temperature, resonator temperature, lamp excitation frequency, etc..)
> >> I'd be grateful. It's sad that Symmetricom's manual is not able to
> >> provide any useful details.
> >>
> >> Cheers!
> >>
> >> --
> >> Germán Herrera
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Satelles PNT from Iridium satellites

[Bob kb8tq]

Hi

Oddly enough, the two share a direct connection:

"Report on NBS Dual Mixeer Time Difference System (DMTD) Built
for Time-Domain Measurements Associated with Phase 1 of GPS"

https://tf.nist.gov/general/pdf/84.pdf 

Came out in Jan 1976

Starting in 1980, they had at least one paper a year on one or another
aspect of GPS timing. The first one:

ACCURATE TIME AND FREQUENCY TRANSFER DURING COMMON-VIEW OF A GPS SATELLITE 

https://tf.nist.gov/general/pdf/192.pdf 


Was the one that got a lot of people to sit up and notice GPS as a time source.

Bob


> On Aug 10, 2020, at 12:10 PM, ew  wrote:
> 
> I did attend those conferences, it was my first ex poser to Dual Mixer, NIST 
> presented it for high precision frequency measurements. Still have copies of 
> the proceedings.Time is and was key but I do not recall any papers addressing 
> using GPS for time distribution as we know it today, and that is what I was 
> responding to the question that I answered to. Also writing the proposals and 
> attending all project reviews it was never covered.
>  
> Bert Kehren
>  
>  
>  
> In a message dated 8/10/2020 10:48:12 AM Eastern Standard Time, kb...@n1k.org 
> writes:
>  
> Hi
> 
> From what I saw as the system was developed, the people doing it realized 
> that timing
> was at the core of the design. If there was a timing problem, nothing was 
> going to work.
> There were GPS (and before that other sat-nav) presentations at the Frequency 
> Control
> Symposium for many years. The “big boys” in timing all were involved in GPS 
> one way 
> or the other. 
> 
> NIST was doing time transfer work on GPS before the system was fully up and 
> running. 
> Their results are (to a great degree) what got everybody believing  that GPS 
> *could* 
> be a good source of time. Those papers started early and kept on flowing …. 
> Until they
> put their “stamp of approval” on the technique, I don’t think anybody was 
> ready to call it
> a super time source.
> 
> This is by no means to imply that NIST was the only outfit involved or that 
> the others
> who also evaluated GPS somehow did not contribute. That’s far from the case. 
> The only
> point is that NIST got out there early. 
> 
> Bob
> 
> > On Aug 10, 2020, at 5:09 AM, ew via time-nuts  > > wrote:
> > 
> > Attached are two pictures from my TI days as program Manager of the first 
> > GPS. There was no discussions of consumer use or timing application. Focus 
> > was on military application being able to guide a bomb in to a chimney. The 
> > cost per device was $ 300 000. Because of my high security clearance I was 
> > asked to brief the NSA and CIA on the future of GPS equipment. With my 
> > semiconductor background Moores Law and previously involved in consumer 
> > calculator development I predicted the size of a brick and $ 3000.  I was 
> > declared the company Idiot lost all credibility as a strategic thinker ans 
> > subsequently left TI. When Magellan came out with there handheld unit they 
> > remembered me and send me one. Still have it. When two years later the 
> > units the size of a cigarette pack came out and where given away if you 
> > took a Cadillac test drive the asked for it back. I refused. History.Bert 
> > KehrenIn a message dated 8/9/2020 11:23:33 PM Eastern Standard Time, 
> > time-nuts@lists.febo.com  writes: 
> > I've done some quick research.  I do not see timing as one of the services 
> > provided.  I wonder if it can be achieved by just listening into what's 
> > already transmitted (like GPS) and do some math on our side. 
> > 
> > On more broader sense, was GPS originally designed to provide timing 
> > service?  Or is it a byproduct of needing to measure location and speed, 
> > thus it needed a constant signal, and that using it to sync reference 
> > signal is just an ancillary and after-thought use cases?
> > 
> > --- 
> > (Mr.) Taka Kamiya
> > KB4EMF / ex JF2DKG
> > 
> > 
> >On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq  > > wrote:  
> > 
> > Hi
> > 
> > 
> > 
> >> On Aug 9, 2020, at 7:03 PM, Tom Van Baak  >> > wrote:
> >> 
> >> Hi Stu,
> >> 
> >> There's no problem with a semi-commercial posting here. You've been a 
> >> member for a decade and frequent contributor plus the subject matter is 
> >> exactly on-topic. So thanks for posting.
> >> 
> >> I spent a while on your web site and didn't uncover a trove of white 
> >> papers. If you could post some URL's that would be appreciated. You don't 
> >> have to worry about being less accurate than GPS. I mean, there are often 
> >> far more important factors than nanosecond precision.
> > 
> > To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison 
> > system. Saying that 
> > this or that is better or worse at this 

Re: [time-nuts] Satelles PNT from Iridium satellites

[ew via time-nuts]

I did attend those conferences, it was my first ex poser to Dual Mixer, NIST 
presented it for high precision frequency measurements. Still have copies of 
the proceedings.Time is and was key but I do not recall any papers addressing 
using GPS for time distribution as we know it today, and that is what I was 
responding to the question that I answered to. Also writing the proposals and 
attending all project reviews it was never covered. Bert Kehren   In a message 
dated 8/10/2020 10:48:12 AM Eastern Standard Time, kb...@n1k.org writes: 
Hi

From what I saw as the system was developed, the people doing it realized that 
timing
was at the core of the design. If there was a timing problem, nothing was going 
to work.
There were GPS (and before that other sat-nav) presentations at the Frequency 
Control
Symposium for many years. The “big boys” in timing all were involved in GPS one 
way 
or the other. 

NIST was doing time transfer work on GPS before the system was fully up and 
running. 
Their results are (to a great degree) what got everybody believing  that GPS 
*could* 
be a good source of time. Those papers started early and kept on flowing …. 
Until they
put their “stamp of approval” on the technique, I don’t think anybody was ready 
to call it
a super time source.

This is by no means to imply that NIST was the only outfit involved or that the 
others
who also evaluated GPS somehow did not contribute. That’s far from the case. 
The only
point is that NIST got out there early. 

Bob

> On Aug 10, 2020, at 5:09 AM, ew via time-nuts  
> wrote:
> 
> Attached are two pictures from my TI days as program Manager of the first 
> GPS. There was no discussions of consumer use or timing application. Focus 
> was on military application being able to guide a bomb in to a chimney. The 
> cost per device was $ 300 000. Because of my high security clearance I was 
> asked to brief the NSA and CIA on the future of GPS equipment. With my 
> semiconductor background Moores Law and previously involved in consumer 
> calculator development I predicted the size of a brick and $ 3000.  I was 
> declared the company Idiot lost all credibility as a strategic thinker ans 
> subsequently left TI. When Magellan came out with there handheld unit they 
> remembered me and send me one. Still have it. When two years later the units 
> the size of a cigarette pack came out and where given away if you took a 
> Cadillac test drive the asked for it back. I refused. History.Bert Kehren    
> In a message dated 8/9/2020 11:23:33 PM Eastern Standard Time, 
> time-nuts@lists.febo.com writes: 
> I've done some quick research.  I do not see timing as one of the services 
> provided.  I wonder if it can be achieved by just listening into what's 
> already transmitted (like GPS) and do some math on our side. 
> 
> On more broader sense, was GPS originally designed to provide timing service? 
>  Or is it a byproduct of needing to measure location and speed, thus it 
> needed a constant signal, and that using it to sync reference signal is just 
> an ancillary and after-thought use cases?
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>    On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq  
>wrote:  
> 
> Hi
> 
> 
> 
>> On Aug 9, 2020, at 7:03 PM, Tom Van Baak  wrote:
>> 
>> Hi Stu,
>> 
>> There's no problem with a semi-commercial posting here. You've been a member 
>> for a decade and frequent contributor plus the subject matter is exactly 
>> on-topic. So thanks for posting.
>> 
>> I spent a while on your web site and didn't uncover a trove of white papers. 
>> If you could post some URL's that would be appreciated. You don't have to 
>> worry about being less accurate than GPS. I mean, there are often far more 
>> important factors than nanosecond precision.
> 
> To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison 
> system. Saying that 
> this or that is better or worse at this or that tau is *not* the same as 
> saying it has more or less value. 
> It’s simply a system that is out there to be compared to.
> 
> Bob
> 
> 
>> You didn't mention pricing; it's hard to imagine it's as free as GPS so that 
>> seems like another disadvantage to me.
>> 
>> Your comment about fewer satellites is spot on. That will be taken care of 
>> if you give SpaceX / Starlink a call and join that bandwagon. There are 
>> already 597 Starlink [1] satellites up there vs. 82 Iridium [2] satellites, 
>> yes?
>> 
>> If you have entry-level / hobbyist grade evaluation kits I'm sure a number 
>> of us would be very interested to try it out.
>> 
>> Thanks,
>> /tvb
>> 
>> [1] https://en.wikipedia.org/wiki/Starlink
>> 
>> [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
>> 
>> 
>> On 8/9/2020 2:53 PM, Stewart Cobb wrote:
>>> Taka Kamiya and Forrest Christian both asked recently about the alternative
>>> satellite PNT system using the Iridium satellites. That system was
>>> 

Re: [time-nuts] Symmetricom X72

[Germán Herrera]

Hi Paul,

First of all, thank you for your advice.

I did try with the cover on, and also with the magnetic shield on (which 
consists of about three sheets of mu metal wrapped around the resonator 
cavity over and below the board (you can see the slits on the bigger 
board, on the pictures).


I've had mixed results, with the unit warmed up but without the cover, I 
had the opportunity to have it locked for quite some time (about 8 
hours) before powering it off again. Other times it doesn't lock. Other 
times where the unit starts cold, after a couple of minutes locks for a 
short (~30s) time and gets back to sweeping frequency (unlocked state). 
I've seen that happen on an Efratom FRK with a defective resonator 
thermistor, that's why my main suspect is the temperature.


I still have pending to attach the scope to the photodector amplifier to 
check if I see the modulation signal. After that I think it all goes 
digital so there's nothing much I can do. I did try varying the lamp 
oscillator frequency but didn't notice any effect (kind of a long shot 
since I don't know the right frequency), so I left it as it originally 
was.


Kind regards!

---
Germán Herrera
Responsable IT
Ingeniería
SES Sistemas Electrónicos S.A.| Espinosa 1045 (C1405AMM) | Buenos Aires 
| Argentina

W: +54 11 54538426 | Email: g.herr...@ses.com.ar

On 2020-08-10 10:21, paul swed wrote:

German have you tried with the cover back on?
The external light in your picture could be affecting the system.
The color of the RB lamp looks about right and its nice and bright.
Also most Rbs I have worked on tend to insulate the various ovens and 
such.

Temperature matters.
Regards
Paul

On Mon, Aug 10, 2020 at 9:15 AM Germán Herrera  
wrote:



Hi everyone

This is my first post on the list, tought I've been subscribed for 
some

time.
I'm in the process of troubleshooting an X72 which recently started to
be unable to acquire lock. I've searched online for pics of this
standard and wasn't unable to find anything, so i took some nice
pictures which I'd like to share with you:


https://drive.google.com/drive/folders/1HN8dms5CxPwUjdckEux2fOVTF5IoaI5u?usp=sharing

After disassembling it I found that an optical filter which is 
supposed

to be glued to the light path of the lamp was loose inside the unit. I
attached it again but the issue persisted.

If anyone is able any information about the thing (such as lamp 
working

temperature, resonator temperature, lamp excitation frequency, etc..)
I'd be grateful. It's sad that Symmetricom's manual is not able to
provide any useful details.

Cheers!

--
Germán Herrera

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.


___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Satelles PNT from Iridium satellites

[dikshie]

Hi Kamiya san,

I know there is only one company in Japan that uses STL service from
Iridium (via Spectracom as Vendor).
However I cant disclose the information more detail.

Best Regards,

Dikshie

On Mon, Aug 10, 2020 at 12:23 PM Taka Kamiya via time-nuts
 wrote:
>
> I've done some quick research.  I do not see timing as one of the services 
> provided.  I wonder if it can be achieved by just listening into what's 
> already transmitted (like GPS) and do some math on our side.
>
> On more broader sense, was GPS originally designed to provide timing service? 
>  Or is it a byproduct of needing to measure location and speed, thus it 
> needed a constant signal, and that using it to sync reference signal is just 
> an ancillary and after-thought use cases?
>
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
>
>
> On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq  
> wrote:
>
>  Hi
>
>
>
> > On Aug 9, 2020, at 7:03 PM, Tom Van Baak  wrote:
> >
> > Hi Stu,
> >
> > There's no problem with a semi-commercial posting here. You've been a 
> > member for a decade and frequent contributor plus the subject matter is 
> > exactly on-topic. So thanks for posting.
> >
> > I spent a while on your web site and didn't uncover a trove of white 
> > papers. If you could post some URL's that would be appreciated. You don't 
> > have to worry about being less accurate than GPS. I mean, there are often 
> > far more important factors than nanosecond precision.
>
> To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison 
> system. Saying that
> this or that is better or worse at this or that tau is *not* the same as 
> saying it has more or less value.
> It’s simply a system that is out there to be compared to.
>
> Bob
>
>
> > You didn't mention pricing; it's hard to imagine it's as free as GPS so 
> > that seems like another disadvantage to me.
> >
> > Your comment about fewer satellites is spot on. That will be taken care of 
> > if you give SpaceX / Starlink a call and join that bandwagon. There are 
> > already 597 Starlink [1] satellites up there vs. 82 Iridium [2] satellites, 
> > yes?
> >
> > If you have entry-level / hobbyist grade evaluation kits I'm sure a number 
> > of us would be very interested to try it out.
> >
> > Thanks,
> > /tvb
> >
> > [1] https://en.wikipedia.org/wiki/Starlink
> >
> > [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
> >
> >
> > On 8/9/2020 2:53 PM, Stewart Cobb wrote:
> >> Taka Kamiya and Forrest Christian both asked recently about the alternative
> >> satellite PNT system using the Iridium satellites. That system was
> >> developed by my company, Satelles. It has been commercially available for
> >> more than a year now.
> >>
> >> The biggest advantage is that our signal is at least 30 dB stronger than
> >> GNSS signals (the exact numbers depend on whether you're talking to
> >> engineering or marketing :). You can easily get a usable signal in deep
> >> jungle, or a data center in the middle of a building's basement, or even
> >> inside a locked shipping container. The stronger signal is correspondingly
> >> more difficult to jam or spoof than GNSS, and our signal has anti-spoofing
> >> features as well.
> >>
> >> The biggest disadvantage is that it is not quite as accurate as GPS,
> >> because there are fewer satellites in view at any given time.
> >>
> >> I don't want to quote exact timing numbers here, because they depend a lot
> >> on system integration details, but you can easily steer an OCXO within a
> >> few hundred nanoseconds of USNO time. With a rubidium, you can do
> >> considerably better.
> >>
> >> If you want to know more, our website is www.satellesinc.com.
> >>
> >> (If this message has been too commercial, I apologize in advance. The
> >> boundary between information and salesmanship is not always sharp.)
> >>
> >> Cheers!
> >> --Stu
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to 
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to 
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.



-- 
-dikshie-

___
time-nuts mailing list -- time-nuts@lists.febo.com

Re: [time-nuts] Satelles PNT from Iridium satellites

[Bob kb8tq]

Hi

From what I saw as the system was developed, the people doing it realized that 
timing
was at the core of the design. If there was a timing problem, nothing was going 
to work.
There were GPS (and before that other sat-nav) presentations at the Frequency 
Control
Symposium for many years. The “big boys” in timing all were involved in GPS one 
way 
or the other. 

NIST was doing time transfer work on GPS before the system was fully up and 
running. 
Their results are (to a great degree) what got everybody believing  that GPS 
*could* 
be a good source of time. Those papers started early and kept on flowing …. 
Until they
put their “stamp of approval” on the technique, I don’t think anybody was ready 
to call it
a super time source.

This is by no means to imply that NIST was the only outfit involved or that the 
others
who also evaluated GPS somehow did not contribute. That’s far from the case. 
The only
point is that NIST got out there early. 

Bob

> On Aug 10, 2020, at 5:09 AM, ew via time-nuts  
> wrote:
> 
> Attached are two pictures from my TI days as program Manager of the first 
> GPS. There was no discussions of consumer use or timing application. Focus 
> was on military application being able to guide a bomb in to a chimney. The 
> cost per device was $ 300 000. Because of my high security clearance I was 
> asked to brief the NSA and CIA on the future of GPS equipment. With my 
> semiconductor background Moores Law and previously involved in consumer 
> calculator development I predicted the size of a brick and $ 3000.  I was 
> declared the company Idiot lost all credibility as a strategic thinker ans 
> subsequently left TI. When Magellan came out with there handheld unit they 
> remembered me and send me one. Still have it. When two years later the units 
> the size of a cigarette pack came out and where given away if you took a 
> Cadillac test drive the asked for it back. I refused. History.Bert Kehren
> In a message dated 8/9/2020 11:23:33 PM Eastern Standard Time, 
> time-nuts@lists.febo.com writes: 
> I've done some quick research.  I do not see timing as one of the services 
> provided.  I wonder if it can be achieved by just listening into what's 
> already transmitted (like GPS) and do some math on our side. 
> 
> On more broader sense, was GPS originally designed to provide timing service? 
>  Or is it a byproduct of needing to measure location and speed, thus it 
> needed a constant signal, and that using it to sync reference signal is just 
> an ancillary and after-thought use cases?
> 
> --- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
> On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq  
> wrote:  
> 
> Hi
> 
> 
> 
>> On Aug 9, 2020, at 7:03 PM, Tom Van Baak  wrote:
>> 
>> Hi Stu,
>> 
>> There's no problem with a semi-commercial posting here. You've been a member 
>> for a decade and frequent contributor plus the subject matter is exactly 
>> on-topic. So thanks for posting.
>> 
>> I spent a while on your web site and didn't uncover a trove of white papers. 
>> If you could post some URL's that would be appreciated. You don't have to 
>> worry about being less accurate than GPS. I mean, there are often far more 
>> important factors than nanosecond precision.
> 
> To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison 
> system. Saying that 
> this or that is better or worse at this or that tau is *not* the same as 
> saying it has more or less value. 
> It’s simply a system that is out there to be compared to.
> 
> Bob
> 
> 
>> You didn't mention pricing; it's hard to imagine it's as free as GPS so that 
>> seems like another disadvantage to me.
>> 
>> Your comment about fewer satellites is spot on. That will be taken care of 
>> if you give SpaceX / Starlink a call and join that bandwagon. There are 
>> already 597 Starlink [1] satellites up there vs. 82 Iridium [2] satellites, 
>> yes?
>> 
>> If you have entry-level / hobbyist grade evaluation kits I'm sure a number 
>> of us would be very interested to try it out.
>> 
>> Thanks,
>> /tvb
>> 
>> [1] https://en.wikipedia.org/wiki/Starlink
>> 
>> [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
>> 
>> 
>> On 8/9/2020 2:53 PM, Stewart Cobb wrote:
>>> Taka Kamiya and Forrest Christian both asked recently about the alternative
>>> satellite PNT system using the Iridium satellites. That system was
>>> developed by my company, Satelles. It has been commercially available for
>>> more than a year now.
>>> 
>>> The biggest advantage is that our signal is at least 30 dB stronger than
>>> GNSS signals (the exact numbers depend on whether you're talking to
>>> engineering or marketing :). You can easily get a usable signal in deep
>>> jungle, or a data center in the middle of a building's basement, or even
>>> inside a locked shipping container. The stronger signal is correspondingly
>>> more difficult to jam or spoof than GNSS, and our signal has 

Re: [time-nuts] Symmetricom X72

[paul swed]

German have you tried with the cover back on?
The external light in your picture could be affecting the system.
The color of the RB lamp looks about right and its nice and bright.
Also most Rbs I have worked on tend to insulate the various ovens and such.
Temperature matters.
Regards
Paul

On Mon, Aug 10, 2020 at 9:15 AM Germán Herrera  wrote:

> Hi everyone
>
> This is my first post on the list, tought I've been subscribed for some
> time.
> I'm in the process of troubleshooting an X72 which recently started to
> be unable to acquire lock. I've searched online for pics of this
> standard and wasn't unable to find anything, so i took some nice
> pictures which I'd like to share with you:
>
>
> https://drive.google.com/drive/folders/1HN8dms5CxPwUjdckEux2fOVTF5IoaI5u?usp=sharing
>
> After disassembling it I found that an optical filter which is supposed
> to be glued to the light path of the lamp was loose inside the unit. I
> attached it again but the issue persisted.
>
> If anyone is able any information about the thing (such as lamp working
> temperature, resonator temperature, lamp excitation frequency, etc..)
> I'd be grateful. It's sad that Symmetricom's manual is not able to
> provide any useful details.
>
> Cheers!
>
> --
> Germán Herrera
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

[time-nuts] Symmetricom X72

[Germán Herrera]

Hi everyone

This is my first post on the list, tought I've been subscribed for some 
time.
I'm in the process of troubleshooting an X72 which recently started to 
be unable to acquire lock. I've searched online for pics of this 
standard and wasn't unable to find anything, so i took some nice 
pictures which I'd like to share with you:


https://drive.google.com/drive/folders/1HN8dms5CxPwUjdckEux2fOVTF5IoaI5u?usp=sharing

After disassembling it I found that an optical filter which is supposed 
to be glued to the light path of the lamp was loose inside the unit. I 
attached it again but the issue persisted.


If anyone is able any information about the thing (such as lamp working 
temperature, resonator temperature, lamp excitation frequency, etc..) 
I'd be grateful. It's sad that Symmetricom's manual is not able to 
provide any useful details.


Cheers!

--
Germán Herrera

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.

Re: [time-nuts] Satelles PNT from Iridium satellites

[John Maxwell]

On 08/09/2020 09:33:07 PM, Taka Kamiya via time-nuts wrote:
[snip]
> On more broader sense, was GPS originally designed to provide timing
> service?  Or is it a byproduct of needing to measure location and
> speed, thus it needed a constant signal, and that using it to sync
> reference signal is just an ancillary and after-thought use cases?

A little of both. The desire on the customer's part (i.e., what the US
military wanted) was accurate rapidly updatable location information.
But the approach used for GPS also required the receiver to precisely
compute the time as well.

So, it wasn't in the requirements, but it is inherent in the design.

-John

--
John Maxwell  KB3VLL  j...@jmaxhome.com

___
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to 
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.