Re: [time-nuts] HP 58540A GPSDO date

[Hal Murray]

jg...@zianet.com said:
> All this talk of GPS week rollover reminds me of a problem that I am having
> with my HP 58540A since I moved. I can't seem to set the correct date.
> Perhaps someone here knows the magic formula. 

For the Z3801A:
  power off
  unplug antenna
  power on
  set data
  reconnect antenna

That doesn't work with the KS-24361m or I've lost my touch, or ...


-- 
These are my opinions.  I hate spam.




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Re: [time-nuts] WWVB Disciplined Oscillator

[Kevin Croissant]

Hi Wayne,

Great to see you found my presentation!
The paper is available here:
https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018_paper.pdf
I traveled to CO and met with NIST people there and gathered more data
then. We're planning to put out another paper soon (I'm finishing up my
bachelor's right now so I'm a bit preoccupied though).
I think LF timing is still very relevant in this day and age, and WWVB
still shows promise as a national timing source.

Let me know if you have any questions.
Best,
Kevin

On Sat, Apr 6, 2019 at 10:00 PM paul swed  wrote:

> Wayne good read on the paper.
> All of the spectracoms and such were rendered useless by the new BPSK
> modulation. Though now that 5 years or so have passed not so new. Unless
> the modulation is accounted for they can't track the carrier. There are
> external modifications and other approaches that have been suggested. I
> have design and tested numbers of them with a final approach using the
> cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts
> enough. A lot depends on your location and signal strength. Clearly taking
> advantage of the new modulation for carrier prediction has advantage. But
> the fact is even I am now spoiled by GPSDOs.
> I also built a far simplere approach called a remodulator for simply
> allowing the spectracoms to get time. They are nice displays. Not sure you
> can get even those piece parts any longer.
> Regards
> Paul
> WB8TSL
>
> On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder 
> wrote:
>
> > Perhaps this has been mention before, but I found the following document
> > while researching some details on WWVB and thought it might interest the
> > group:
> >
> >   https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf
> >
> > I know that Spectracom once made a WWVB Disciplined Oscillator in the
> form
> > of the Model 8164, but I figured that this approach probably was obsolete
> > in the era of GPS and network-based time. However, the author seems to
> have
> > produced some interesting results.  Has anyone else built, or tried to
> > build a WWVB Disciplined Oscillator?
> >
> > Wayne
> > ___
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> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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-- 
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[time-nuts] Rollover: Trimble Resolution T

[Michael Wouters]

Some older ResTs with v1.2 firmware stopped tracking 15 minutes after the
rollover but recovered trackingafter a hard reset. UTC time of day in the
8FAB message has stepped back 20 years, unsurprisingly.

Cheers
Michael
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[time-nuts] HP 58540A GPSDO date

[Joseph Gray]

All this talk of GPS week rollover reminds me of a problem that I am having
with my HP 58540A since I moved. I can't seem to set the correct date.
Perhaps someone here knows the magic formula.

I am positive that when I had the 58540A running in my previous location
(NM), that I had managed to set the correct date. Ever since setting up the
58540A at my new location (NV), I can't set the correct date, no matter
what I try. I just messed with this again earlier today.

Upon a fresh powerup, the command :GPS:INIT:DATE 2019,4,6 does set the
date, but as soon as the 58540A gets the data from the satellites, it sets
the date to 1999,8,21. After this happens, the command :PTIME:DATE 2019,4,6
just gives an error.

During  powerup, the command :PTIME:DATE 2019,4,6 gives an error. After
satellites are acquired, the command GPS:INIT:DATE 2019, 4,6 gives an error.

As for the week rollover, since the 58540A was already on 1999, the
rollover didn't seem to make any difference.

Joe Gray
W5JG
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Re: [time-nuts] Rollover : Thunderbolt

[Dana Whitlow]

My ancient T'bolt (purchased well-used several months ago) also went from
1023 to
1024.  A quick look at IQ phase data I was recording (referred to a
free-running PRS-10)
shows no discernible glitch at the moment of rollover.

This old T'bolt has been living in 1999 for as long as I've had it.  So
tonight it went from
Aug 21, 1999 to Aug 22, 1999.  I'll be interested in seeing what that date
does over the
next several months.

I also have a CNS Clock II, which went smoothly to week 2048, and it  shows
the
correct UTC date.  I confess that I forgot to see what week # it showed
before the
big event, but suspect it was 2047 (not 1023).  Shame on me!

Dana


On Sat, Apr 6, 2019 at 9:01 PM paul swed  wrote:

> HP 3801 locked after the rollover. Thats all I have checked so far.
> Regards
> Paul
>
> On Sat, Apr 6, 2019 at 9:01 PM Martin VE3OAT  wrote:
>
> > Well!  I must have misunderstood something.  At 23:59:42 on 06 April,
> > LadyHeather informed me that my Thunderbolt changed from week number
> > 1023 to 1024.
> >
> > Drama!  Suspense!  Excitement!  I had expected a reset from 1023 to
> > 0.  But that isn't what happened.  Maybe in another 20 years ...
> >
> > 73,
> >
> > ... Martin   VE3OAT
> >
> >
> >
> >
> >
> > ___
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> >
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Re: [time-nuts] WWVB Disciplined Oscillator

[paul swed]

Wayne good read on the paper.
All of the spectracoms and such were rendered useless by the new BPSK
modulation. Though now that 5 years or so have passed not so new. Unless
the modulation is accounted for they can't track the carrier. There are
external modifications and other approaches that have been suggested. I
have design and tested numbers of them with a final approach using the
cheat'n d-psk-r. Won't go into that as its been shared here on time-nuts
enough. A lot depends on your location and signal strength. Clearly taking
advantage of the new modulation for carrier prediction has advantage. But
the fact is even I am now spoiled by GPSDOs.
I also built a far simplere approach called a remodulator for simply
allowing the spectracoms to get time. They are nice displays. Not sure you
can get even those piece parts any longer.
Regards
Paul
WB8TSL

On Sat, Apr 6, 2019 at 8:00 PM Wayne Holder  wrote:

> Perhaps this has been mention before, but I found the following document
> while researching some details on WWVB and thought it might interest the
> group:
>
>   https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf
>
> I know that Spectracom once made a WWVB Disciplined Oscillator in the form
> of the Model 8164, but I figured that this approach probably was obsolete
> in the era of GPS and network-based time. However, the author seems to have
> produced some interesting results.  Has anyone else built, or tried to
> build a WWVB Disciplined Oscillator?
>
> Wayne
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[time-nuts] GPS week rollover

[Gary Myers]

I thought for sure my Motorola Oncore receiver in my older Tom Clark's
Tac2 would rollover today at 23:59:42 UTC. Using CNS's tac32 software it
took me in to gps week 2048 without a hitch. 

>From the log: 

-> @@Bo - UTC offset = 18 seconds
-> @@Ea,04/07/2019, 00:00:21.000117714, 1.71986531e+008, 

@@Cj

COPYRIGHT 1991-1997 MOTOROLA INC.
SFTW P/N # 98-P36848P 
SOFTWARE VER # 3  
SOFTWARE REV # 1  
SOFTWARE DATE  May 28 1999
MODEL #R5222U1114 
HWDR P/N # 5  
SERIAL #   R0AZUG 
MANUFACTUR DATE 1A30  

Cheers! 

Gary
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[time-nuts] Rollover : Thunderbolt

[Mark Sims]

Thunderbolts have a rollover date based upon the firmware build date.  That 
delays the week rollover.  They went into rollover mode around May-June of 2017.
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Re: [time-nuts] Rollover : Thunderbolt

[paul swed]

HP 3801 locked after the rollover. Thats all I have checked so far.
Regards
Paul

On Sat, Apr 6, 2019 at 9:01 PM Martin VE3OAT  wrote:

> Well!  I must have misunderstood something.  At 23:59:42 on 06 April,
> LadyHeather informed me that my Thunderbolt changed from week number
> 1023 to 1024.
>
> Drama!  Suspense!  Excitement!  I had expected a reset from 1023 to
> 0.  But that isn't what happened.  Maybe in another 20 years ...
>
> 73,
>
> ... Martin   VE3OAT
>
>
>
>
>
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Re: [time-nuts] WWVB Disciplined Oscillator

[Adrian Godwin]

Not personally, but in the UK a company called Quarztlock made both MSF
(similar to WWVB) and 198kHz (a frequency-standard broadcast station) that
were popular frequency standards in labs.

They still exist but have replaced those products with Rubidium and GPS
based standards.
http://www.quartzlock.com/

On Sun, Apr 7, 2019 at 1:00 AM Wayne Holder  wrote:

> Perhaps this has been mention before, but I found the following document
> while researching some details on WWVB and thought it might interest the
> group:
>
>   https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf
>
> I know that Spectracom once made a WWVB Disciplined Oscillator in the form
> of the Model 8164, but I figured that this approach probably was obsolete
> in the era of GPS and network-based time. However, the author seems to have
> produced some interesting results.  Has anyone else built, or tried to
> build a WWVB Disciplined Oscillator?
>
> Wayne
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Re: [time-nuts] WWVB Disciplined Oscillator

[Bob kb8tq]

Hi

The gotcha with WWVB is correcting for the day / night ionosphere issues. Since 
they are not 
100% predictable, it’s not a real easy problem to solve. Toss on top of the the 
ambiguous status
of WWV or WWVB ( = will it be there next year …. if so in what format ….) 
there layers and 
layers.

Best guess is that WWVB at a “one day” sort of range is a 10 ppt sort of thing. 
At the same observation
time, GPS is a < 0.1 ppt sort of thing. If the objective is accuracy … WWVB 
come in a bit far back ….

Bob

> On Apr 6, 2019, at 7:27 PM, Wayne Holder  wrote:
> 
> Perhaps this has been mention before, but I found the following document
> while researching some details on WWVB and thought it might interest the
> group:
> 
>  https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf
> 
> I know that Spectracom once made a WWVB Disciplined Oscillator in the form
> of the Model 8164, but I figured that this approach probably was obsolete
> in the era of GPS and network-based time. However, the author seems to have
> produced some interesting results.  Has anyone else built, or tried to
> build a WWVB Disciplined Oscillator?
> 
> Wayne
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Re: [time-nuts] Rollover : Thunderbolt

[Martin VE3OAT]

Well!  I must have misunderstood something.  At 23:59:42 on 06 April, 
LadyHeather informed me that my Thunderbolt changed from week number 
1023 to 1024.


Drama!  Suspense!  Excitement!  I had expected a reset from 1023 to 
0.  But that isn't what happened.  Maybe in another 20 years ...


73,

... Martin   VE3OAT





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[time-nuts] WWVB Disciplined Oscillator

[Wayne Holder]

Perhaps this has been mention before, but I found the following document
while researching some details on WWVB and thought it might interest the
group:

  https://www.kevincroissant.com/WWVB/WWVB_PTTI_2018.pdf

I know that Spectracom once made a WWVB Disciplined Oscillator in the form
of the Model 8164, but I figured that this approach probably was obsolete
in the era of GPS and network-based time. However, the author seems to have
produced some interesting results.  Has anyone else built, or tried to
build a WWVB Disciplined Oscillator?

Wayne
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[time-nuts] EFRATOM MFST rollover way before 6/4 23:59:59

[Giorgio Barinetti]

Gents,


i realized that my EFRATOM MFST mainframe Rb + OXCO  with GPS has rolled over 
many months before expeted.

This summer, in August 21, the display has rolled over to 21/08/1999, and 
stayed locked then.

I wasn't aware, since the unit is located in a rack away from my working desk, 
but since i've a logging PC
Connected to the serial port, saving the logs from the GPS,tonight  i've found 
the rollover event.

Did someone notice something similar ?


Btw, happy rollover night...
Giorgio






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Re: [time-nuts] GPS 50 bps recording today

[Mike Cook]

Ok.
I have a bin file recording going via winoncore12 of the Raw data from an M12 .
I hope that it is OK. 
Mike


> Le 6 avr. 2019 à 21:14, Tom Van Baak  a écrit :
> 
> Would someone be a hero and record the raw subframe data from GPS today? It's 
> only 50 bits per second (that's about 8 bytes/second) per SV.
> 
> A select few GPS receivers have binary commands that return this low level of 
> detail: M12 (@@Tr), SiRF (8), uBlox (RXM-SFRB).
> 
> My attempts to pull this off today have failed. It's your once* in a lifetime 
> chance to record a GPS WNRO at the bit level. I'm looking for the raw serial 
> data stream binary dump; something re-playable in the future, not some ascii 
> output or screen shot.
> 
> /tvb
> 
> 
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"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin


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Re: [time-nuts] GPS 50 bps recording today

[Scott Newell]

At 02:14 PM 4/6/2019, Tom Van Baak wrote:
Would someone be a hero and record the raw subframe data from GPS 
today? It's only 50 bits per second (that's about 8 bytes/second) per SV.


I've two uBlox LEA-6Ts recording RXM-SFRB (0x02 0x11) subframe data 
with crummy indoor antenna positions (rain prevents me from getting 
'em outside).


I also have a uBlox NEO-7N recording the undocumented TRK-SFRBX (0x03 
0x0f) subframe data, with a terrific outdoor antenna placement.


Too bad the tbolt doesn't seem to send the subframe data--lots of 
those on the list.


I'm sure the gfz-potsdam.de archive will have the data in a couple of 
weeks, but that's not quite the same as recording it yourself in 
realtime, is it? ;-)


--
newell N5TNL 



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Re: [time-nuts] GPS week rollover

[Steve Olney]

Hi Jeff,

On 6/04/2019 3:30 pm, Jeff Zambory wrote:

Yes Steve, you are correct.

https://www.gps.gov/

Scroll down a bit and you can find a count down to the roll over. And it states 
the time when it will roll over. Just what you have said.


Thanks !!!

I'll watch that and watch my receivers.

It seems, from posts here, that different receivers exhibit different 
WNRO behaviour - with effects noted *before* the RO epoch.


I am curious about this and set my Garmin 16x to output as per a 
snapshot below...


$PGRMF,1023,590391,060419,195933,18

...which is GPS week, GPS seconds, UTC date, UTC time and leap second count

As GPS seconds wraps around at 604799 (and GPS is incremented at that 
moment) then there is 604799 + 1 - 590391 = 14409 seconds to go from 
19:59:33.


14408 seconds = 4 h 9 seconds.   19:59:33 + 4:00:09 = 23:59:42.

This agrees with the www.gps.gov data.

So why are people reporting effects already ? My *guess* as to why some 
receivers have reacted before the RO epoch is that attempts to address 
the issue have been different depending on the vintage of the GPS receivers.


 * Receivers manufactured just a few years before the first rollover
   data would need to cross the 1023 - 0 week boundary a short-ish time
   after manufacture.   So some kind of offset would need to be added
   to the week number.  These units which have not had firmware updates
   would presumably react early to the second rollover depending on the
   date of manufacture.
 * Receivers manufactured after the first rollover would presumably
   react late to the second RO by the same logic.
 * Receivers of any manufacture date which has had its firmware updated
   regularly would presumably not be affected as the updates would keep
   pushing the internal wrap around epoch further into the future.
 * Old receivers (like my GPS 35 with no updates) already have gone
   through one rollover (currently showing 21 August 1999) and will
   presumably go back to 1980 dates with this rollover.

So - my bottom-line note to myself about this is that just because a 
receiver looks fine tomorrow doesn't mean it won't fall over next week, 
or next month, or next year, etc.


Cheers

Steve

P.S. for some reason time-nut posts arrive in my inbox uncorrelated to 
their time stamps.  So I find myself replying to later posts before 
earlier ones.  Gets a bit confusing for this Senior Citizen... LOL...


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[time-nuts] GPS 50 bps recording today

[Tom Van Baak]

Would someone be a hero and record the raw subframe data from GPS today? It's 
only 50 bits per second (that's about 8 bytes/second) per SV.

A select few GPS receivers have binary commands that return this low level of 
detail: M12 (@@Tr), SiRF (8), uBlox (RXM-SFRB).

My attempts to pull this off today have failed. It's your once* in a lifetime 
chance to record a GPS WNRO at the bit level. I'm looking for the raw serial 
data stream binary dump; something re-playable in the future, not some ascii 
output or screen shot.

/tvb


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Re: [time-nuts] Garmin GPS12XL V3.51

[Joe Leikhim]

I just checked the Garmin site and indeed there are upgrades to versions 4.60 
and 3.53. It seems that since I have V3.51 I can jump to 3.53 but not 4.60. I 
assume my hardware precedes yours.

"Mine had the batteries out for about a year.? Put some fresh ones in, turned it
on and set it outside for several minutes. It located position and is showing
today's date and time just fine.? Software version on mine is 4.58.

Wes"

--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM


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Re: [time-nuts] GPS week rollover

[Mike Cook]

> Le 6 avr. 2019 à 17:53, jimlux  a écrit :
> 
> On 4/6/19 12:53 AM, Mike Cook wrote:
>> The OP doesn’t state where he got the  « quote » from, but IMHO it is wrong. 
>> As I understand it.
>> The GPS epoch started at 0h 1st June 1980
> 
> 6 Jan 1980 00:00:00 UTC

Just so… 01/06  tripped me

> 
> 
> 
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"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin


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[time-nuts] Navsync CW25 rollover

[Mark Sims]

I recently got in a Navsync CW25 based receiver and added support for it to 
Lady Heather.  

I found some info that says current firmware will be affected by the 
rollover... in a major way!  When the week reaches 0, it stops tracking sats 
for the whole week.   Conner-Winfield has updated firmware for the affected 
devices.  The updates are in a .rar file that requires winrar 5.xx to extract.  
 The CW25 is the only receiver that I know of that actually stops working 
because of rollover.
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Re: [time-nuts] GPS week rollover

[jimlux]

On 4/6/19 12:53 AM, Mike Cook wrote:

The OP doesn’t state where he got the  « quote » from, but IMHO it is wrong. As 
I understand it.
The GPS epoch started at 0h 1st June 1980


6 Jan 1980 00:00:00 UTC



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Re: [time-nuts] Garmin GPS12XL V3.51

[Wes]

Mine had the batteries out for about a year.  Put some fresh ones in, turned it 
on and set it outside for several minutes. It located position and is showing 
today's date and time just fine.  Software version on mine is 4.58.


Wes

  It had to On 4/6/2019 12:10 AM, David J Taylor via time-nuts wrote:

Just checked my wonderful Garmin GPS12XL tonight. before midnight UTC I
checked navigation and UTC time and all was well. I did not bother to
check date for some reason. Well now April 6 2019 at 03:39:19 UTC I see
the time is 21 August 99 and no apparent way to change. The navigation
and time seem correct.

I heard there was a way to reset these to current date. Any thoughts?
Can I still use this as a tool for gathering waypoints with precision?

Joe Leikhim
==

Joe,

My 12 XL runs 24x7 so I tried switching it off and on, and the date and time 
are still correct, but maybe that's stored data it's using?


When it boots, it shows 4.60 (1966-2003) as the software, so perhaps you can 
update?  Whether that fixes the issue I don't know


Cheers,
David




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Re: [time-nuts] GPS week rollover

[Martin Burnicki]

Steve Olney wrote:
> Just curious - WNRO is not an issue for me even if my GPS receivers are
> affected - but I note that the time of rollover is being quoted as
> 23:59:59 UTC 6th April.
> 
> Wouldn't the time actually be 18 seconds earlier ? - i.e., 23:59:42 -
> due to leap seconds ?
> 
> BTW - I'm not clear about GPS time vs UTC (which is probably relevant to
> the above).  Any pointers to a clear explanation ?

The explanation is simple, IMO.

When the GPS system was put into operation in 1980 then the GPS time
matched UTC.

However, a number of leap seconds have been inserted into the UTC time
scale since, and each leap second delayed UTC by 1 s.

Yet 18 leap seconds have been inserted, so UTC is 18 s behind GPS time,
or the other way round, GPS time is 18 s ahead of UTC, so the WNRO
occurs 18 s before UTC midnight.

BTW, the effects of the rollover have already begun. For example, the
reference times of the almanac and clock correction parameters in the
the navigation messages received from the satellites refer to a time a
in the near future, so the week number of those time stamps has already
rolled over.

Martin

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Re: [time-nuts] GPS week rollover

[Steve Olney]

Hi Martin,

On 6/04/2019 6:44 pm, Martin Burnicki wrote:

Steve Olney wrote:

Wouldn't the time actually be 18 seconds earlier ? - i.e., 23:59:42 -
due to leap seconds ?


Martin Burnicki wrote:

so the WNRO
occurs 18 s before UTC midnight.


So - yes.

Thanks for the clarification.

Cheers

Steve


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Re: [time-nuts] GPS week rollover

[Mike Cook]

The OP doesn’t state where he got the  « quote » from, but IMHO it is wrong. As 
I understand it.
The GPS epoch started at 0h 1st June 1980 and the week number roles at 1024 
week intervals at 0h GPS time. When a leap second is added its as if the clock 
stops for a second so GPS time will be in advance of UTC buy the number of leap 
seconds added.  18 leap seconds have been added to date, so 0h GPS 07 april 
2019 will be crossed at 23:59:42 UTC on April 6 as you indicated.


> Le 6 avr. 2019 à 00:40, Steve Olney  a écrit :
> 
> Just curious - WNRO is not an issue for me even if my GPS receivers are 
> affected - but I note that the time of rollover is being quoted as 23:59:59 
> UTC 6th April.
> 
> Wouldn't the time actually be 18 seconds earlier ? - i.e., 23:59:42 - due to 
> leap seconds ?
> 
> BTW - I'm not clear about GPS time vs UTC (which is probably relevant to the 
> above).  Any pointers to a clear explanation ?
> 
> Cheers
> 
> Steve
> 
> 
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"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin


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Re: [time-nuts] GPS week rollover

[Mike Cook]

I checked my Garmin Emap, 1999 vintage IIRC. That is telling me that it is 
20/05/2014. 

I found this for Trimble which shows a number of devices affected by this which 
are commonly used bt timenuts.



Have a nice day

> Le 28 mars 2019 à 20:21, Steve - Home  a écrit :
> 
> I have a Z3816A that’s showing a yellow “ro” next to the date in LH and is 18 
> seconds ahead of a Motorola 12 channel (and my iPhone). I haven’t had time to 
> look into it as I’m adjusting to “voluntary” retirement and trying to clear 
> out some excess stuff. 
> 
> Steve
> 
> 
> 
> 
>> On Mar 28, 2019, at 1:30 PM,   wrote:
>> 
>> Are we expecting any week rollover problems with the receivers we time
>> nuts like to play with???
>> 
>> Cheers,
>> 
>> Corby
>> 
>> 
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Re: [time-nuts] GPS week rollover

[Jeff Zambory]

Yes Steve, you are correct. 

https://www.gps.gov/

Scroll down a bit and you can find a count down to the roll over. And it states 
the time when it will roll over. Just what you have said. 

Jeff Z. 

Sent from my iPhone

> On Apr 5, 2019, at 4:40 PM, Steve Olney  wrote:
> 
> Just curious - WNRO is not an issue for me even if my GPS receivers are 
> affected - but I note that the time of rollover is being quoted as 23:59:59 
> UTC 6th April.
> 
> Wouldn't the time actually be 18 seconds earlier ? - i.e., 23:59:42 - due to 
> leap seconds ?
> 
> BTW - I'm not clear about GPS time vs UTC (which is probably relevant to the 
> above).  Any pointers to a clear explanation ?
> 
> Cheers
> 
> Steve
> 
> 
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Re: [time-nuts] Lars GPSDO

[Bob kb8tq]

Hi

One thing to watch out for on any OCXO, but more on ones with crazy
large tuning ranges:

As the OCXO changes temperature, it’s current draw changes. It’s amazing
just how much voltage drop you get in some seemingly well laid out boards
when this occurs. The gotcha is that a “bias it up” with a couple resistors 
approach
may or may not help this. It depends on just where the resistors are on 
the board. 

On some specs, they go to the extreme of specifying a point on the ground
lead (after soldering in a board) that is the “official” ground for the 
oscillator. 
Good luck finding that on a data sheet out in the wild …

If you have a 0-5V tuning range and a ~2:1 sensitivity variation over that range
and a 0.25 ppm EFC: 0.5 ppm / 5 = 0.1 ppm / V. A 10 mv shift (which is not 
unusual on a 5V OCXO) gets you 1x10^-9 of frequency change. If that’s over 
0-50C it’s contributing 2x10^-11 / C. Small changes in air flow quickly change
the oven current so the loop may be having fun ….

Bob

> On Apr 5, 2019, at 10:45 PM, Jim Harman  wrote:
> 
> Thanks for your ideas, Ed. In my actual implementation I am using
> reasonably low tempco 1% fixed resistors. In the photo they are the blue
> resistors between the DAC and the OCXO.
> 
> I have noticed a significant temperature sensitivity in the system,
> especially if I run it with the cover off.so the ambient temperature can
> change quickly. Moving air has a short term effect on the OCXO and to a
> lesser extent the GPS. Sustained ambient temperature changes cause an
> offset in the DAC value when the loop is closed, so the loop is doing its
> job to compensate for them. Putting the system in a small picnic cooler
> with several water bottles makes any temperature changes slower than the
> loop time constant, which should minimize temperature effects on the
> overall system.
> 
> I calculate the open loop temperature sensitivity at about 7e-11 / deg C.
> The C-MAC oscillator spec for what it's worth is  "-10 C to +70 C / ref.at
> +30 C  < +/- 3.0 e-9". If the variation was linear, which I realize it is
> probably not, that would be 7.5e-11 / deg C so I am in the same ballpark.
> 
> On Fri, Apr 5, 2019 at 8:21 PM ed breya  wrote:
> 
>> I'd recommend that once you get things figured out and tuned up to
>> nominal running conditions, you should narrow the offset pot range, and
>> use good low-TC resistors to make up most of the network R, with the pot
>> having as small an effect as practical. BTW I don't see the pot in the
>> pictures, but I do in the schematic.
>> 
>> You may want to consider lowering the entire network resistance by
>> scaling everything down, say ten times lower or more. This would reduce
>> noise, and lessen effects from the varicap bias (leakage) current in the
>> OCXO. Also, I have seen a number of OCXOs with an internal termination
>> resistor (like 50-100 k) on the tuning line - that has spoiled a lot of
>> fun for me, having to worry about the characteristics of that resistor,
>> and including it in the deal. With an unknown or unspecified OCXO, it's
>> good to check for any unwanted extra parts.
>> 
>> It may help the stability to put some insulation around the tuning
>> resistor network and maybe the DAC too, especially if the waste heat
>> from the OCXO is significant.
>> 
>> Ed
>> 
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> 
> 
> -- 
> 
> --Jim Harman
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Re: [time-nuts] Garmin GPS12XL V3.51

[Joe Leikhim]

Thanks! I don't ever think I relied on the date in the unit.  It is 
going to get some use soon. I would have no idea what to replace it with.


Next I need to check out my Symmetricom / /Datum 9390/-/6000/ EXACTIME 
next. The antenna has been off \for a while. It was updated some years 
back to what was the latest and last version.



On 4/6/2019 1:04 AM, Peter Putnam wrote:

From the Garmin web-site at:
https://support.garmin.com/en-US/?faq=jXw3hvTdo24PunZy4yOpX8=87=date%20error=topics


  GPS 12 Time and Date are Incorrect

We’ve identified an issue with this product that causes the date 
and/or time to be wrong after the GPS Rollover on April 6th, 
2019. However, all functions not dependent on date and/or time will 
continue to work normally. Due to the age of the device we have 
determined we will not fix this issue.


*What does that mean for my Garmin**?*

  * The date and/or time determined by the GPS will be wrong
  * Position, velocity, navigation, and all other functionality not
dependent on date and/or time will continue to work normally

*What is GPS Week Rollover?*

The GPS satellite system communicates the date via a week number that 
is limited to 1024 weeks (about 20 years). On April 6th, 2019 the week 
numbers broadcast by the satellites will “rollover” to zero. If GPS 
receivers don’t account for this rollover in their software, it will 
calculate the wrong date and/or time.




On 4/5/2019 8:40 PM, Joe Leikhim wrote:
Just checked my wonderful Garmin GPS12XL tonight. before midnight UTC 
I checked navigation and UTC time and all was well. I did not bother 
to check date for some reason. Well now April 6 2019 at 03:39:19 UTC 
I see the time is 21 August 99 and no apparent way to change. The 
navigation and time seem correct.


I heard there was a way to reset these to current date. Any thoughts? 
Can I still use this as a tool for gathering waypoints with precision?





 
	Virus-free. www.avg.com 
 



<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>


--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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Re: [time-nuts] Garmin GPS12XL V3.51

[Björn]

If you ignore date/year, everything else should be just as before.

—

Björn 

Sent from my iPhone

> On 6 Apr 2019, at 05:40, Joe Leikhim  wrote:
> 
> Just checked my wonderful Garmin GPS12XL tonight. before midnight UTC I 
> checked navigation and UTC time and all was well. I did not bother to check 
> date for some reason. Well now April 6 2019 at 03:39:19 UTC I see the time is 
> 21 August 99 and no apparent way to change. The navigation and time seem 
> correct.
> 
> I heard there was a way to reset these to current date. Any thoughts? Can I 
> still use this as a tool for gathering waypoints with precision?
> 
> -- 
> Joe Leikhim
> 
> 
> Leikhim and Associates
> 
> Communications Consultants
> 
> Oviedo, Florida
> 
> jleik...@leikhim.com
> 
> 407-982-0446
> 
> WWW.LEIKHIM.COM
> 
> 
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Re: [time-nuts] Garmin GPS12XL V3.51

[David J Taylor via time-nuts]

Just checked my wonderful Garmin GPS12XL tonight. before midnight UTC I
checked navigation and UTC time and all was well. I did not bother to
check date for some reason. Well now April 6 2019 at 03:39:19 UTC I see
the time is 21 August 99 and no apparent way to change. The navigation
and time seem correct.

I heard there was a way to reset these to current date. Any thoughts?
Can I still use this as a tool for gathering waypoints with precision?

Joe Leikhim
==

Joe,

My 12 XL runs 24x7 so I tried switching it off and on, and the date and time 
are still correct, but maybe that's stored data it's using?


When it boots, it shows 4.60 (1966-2003) as the software, so perhaps you can 
update?  Whether that fixes the issue I don't know


Cheers,
David
--
SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 



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