Re: [time-nuts] Conditioning Rubidium Oscillators

[Hal Murray]

elfchief-timen...@lupine.org said:
> Are there currently any decent (intended (or at least usable) for
> timekeeping) GPSs that support using L2/L5 for this purpose? Google is
> turning up lots of nothing, for me... 

I don't know of any.  I'm somewhat sure that they don't exist or maybe they 
are hidden in the military sector.

Tom Clark and Rick Hambly work on timing for VLBI.  They run a yearly 
workshop on timing.  Their slides are available on the web.  They use low 
cost L1 gear.  I'm sure they would use something better if it were available 
commercially.  They are starting with Hydrogen Masers so cost cutting on the 
GPS receiver would not be a problem.

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Conditioning Rubidium Oscillators

[Bob Camp]

Hi

What you are looking for are survey receivers with time tag inputs and outputs. 
The Novatel boards are
one example of this. For about $5K you can get a nice new one with all the 
needed options. On the surplus 
market the Trimble NetRS shows up over a 10:1 price range, it may or may not do 
the job since you are looking 
for L5 and it’s L1/L2 only. For L1/L2/L5 you are looking at gear that came out 
in the last couple of years. That will be
expensive. L1/L2 is about the only way to go surplus. 

There are a long line of Ashtech receivers that do or do not have timing, it 
all depends on cables you can only see 
once you have it torn apart in your hot little hand. There are also Trimble’s 
successors to the 15 year old NetRS at 
various price points. 

Bob




> On Mar 14, 2016, at 6:21 PM, Jay Grizzard  
> wrote:
> 
> Are there currently any decent (intended (or at least usable) for timekeeping)
> GPSs that support using L2/L5 for this purpose? Google is turning up lots
> of nothing, for me...
> 
> -j
> 
>> Since it is a ???space weather??? determined thing, with L1 only, all 
>> you can do is guess at confidence levels. The real answer is to go to 
>> L1/L2 or L1/L2/L5 and at least reduce the level of the problem.
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[time-nuts] Thunderbolt monitor kits available doon

[Didier Juges]

Finally, by popular demand, another batch of Thunderbolt Monitors are coming...

Check http://www.ko4bb.com/getsimple/index.php?id=the-thunderbolt-monitor-kit



Didier KO4BB

-- 
Sent from my Moto-X wireless tracker while I do other things.
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Re: [time-nuts] Symmetricom SA.35M Information Request

[Bob Camp]

Hi

Have you contacted Symmetricom? That’s a new enough part that it may be in 
warranty. They have been *very* good about that sort of thing on other Rb’s. 

Bob

> On Mar 14, 2016, at 5:10 PM, Ed Palmer  wrote:
> 
> Does anyone have any info on the Symmetricom SA.35M Miniature Rb Standard?  I 
> have the data sheet, patent document and the MACDEMO program.  Is there 
> anything else available?  For example, I'd like some more explanation of the 
> various parameters read by the MACDEMO program.
> 
> I have a sick unit that I'm exploring.  It won't lock.  The VCXO is sweeping 
> and I've confirmed the presence of the 6.834 GHz RF signal so I'm now looking 
> towards the laser.
> 
> I don't expect that I'll be able to get it working, but it's fun to play with.
> 
> Ed
> 
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Re: [time-nuts] Conditioning Rubidium Oscillators

[Jim Harman]

On Mon, Mar 14, 2016 at 2:37 PM, Lars Walenius 
wrote:

> I read this but couldn´t understand why this is superior to the PI-loop
> with a pre-filter?
>
>
> http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Control-%E2%80%93-A-Different-Approach.pdf
>
> Anybody can say why? Even if regression is very useful the limitation of
> the GPS and ionosphere will be the problem?How much better is it reasonable
> to get??
>

I think the potential benefit of this approach is that it continuously
predicts the long term drift of the oscillator and attempts to compensate
for it. If the drift is reasonably linear, this means that you can use a
larger time constant in the control loop and thus be less sensitive to
short term GPS timing variations, while keeping the phase error close to
zero

Of course if the oscillator drift is not predictable, this won't help and
might even make things worse.

I have done some experiments with an OCXO and a controller design similar
to the one Lars posted some time ago. I plotted the trend in the 3-hour
average DAC values over many days and used Excel to do a least-squares fit
to that data. As long as the oscillator is powered on continuously, this
gives an R^2 of over 90%, so the linearity of the drift is very good. If I
use this slope as a correction factor, i.e. adding X DAC counts per day to
the output of the PI control algorithm, it significantly reduces the
average TIC error at long time constants


-- 

--Jim Harman
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Re: [time-nuts] Conditioning Rubidium Oscillators

[Jay Grizzard]

Are there currently any decent (intended (or at least usable) for timekeeping)
GPSs that support using L2/L5 for this purpose? Google is turning up lots
of nothing, for me...

-j

> Since it is a ???space weather??? determined thing, with L1 only, all 
> you can do is guess at confidence levels. The real answer is to go to 
> L1/L2 or L1/L2/L5 and at least reduce the level of the problem.
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Gedas]

Hi Mark and TU for that information. Most interesting.  I will do as you 
suggested. I also saw on the EEV site that the freq was in fact 
off.I think it is low by a small amount that corresponds to being 
off 2 Hz at 100 GHz.  I suspect for my needs I can consider it close 
enough to 10 MHz.


Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound
This is why some people appear bright until you hear them speak.

On 3/14/2016 1:13 PM, Mark Sims wrote:

I believe that it was mentioned here that the BG7TBL GPSDO disciplined 
oscillator controls the OCXO using a FLL (frequency locked loop) instead of a 
PLL (phase locked loop).  Their implementation causes a slight error in the 
output frequency.  Search the time-nuts archives (best to use Google) for the 
relevant thread(s).


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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Bryan _]

There is a interesting hobbyist level GPS frequency generator project on utube. 
Not time nuts level, but a neat project nonetheless. Uses the Neo-7M. Three 
parts.
https://youtu.be/zZ6tc_ROdfU

-=Bryan=-

> Date: Mon, 14 Mar 2016 16:11:16 -0400
> From: t...@patoka.org
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] BG7TBL GPS Disciplined Source
> 
> 
> I would say its even more convenient to monitor binary format, since its 
> more compact and could be read as a structures
> 
> // u-blox UBX protocol essentials
> 
> typedef struct ubx_header {
>  unsigned char preamble1;
>  unsigned char preamble2;
>  unsigned char msg_class;
>  unsigned char msg_id;
>  unsigned short length;
> } my_ubx_header;
> 
> typedef struct ubx_nav_timegps {
>  unsigned long iTOW_ms;
>  signed long fTOW_ns;
>  signed short week;
>  signed char leapS;
>  unsigned char valid;
>  unsigned long tAcc;
> } my_ubx_nav_timegps;
> 
> typedef struct ubx_nav_timeutc {
>  unsigned long iTOW_ms;
>  unsigned long tAcc_ns;
>  signed long nano;
>  unsigned short year;
>  unsigned char month;
>  unsigned char day;
>  unsigned char hour;
>  unsigned char min;
>  unsigned char sec;
>  unsigned char valid;
> } my_ubx_nav_timeutc;
> 
> and so on...
> 
> 
> On 2016-03-14 15:38, Björn wrote:
> >  Originalmeddelande Från: Gedas
> >  Datum:2016-03-14  19:52  (GMT+01:00)
> > Till: Discussion of precise time and frequency measurement
> >  Rubrik: Re: [time-nuts] BG7TBL GPS
> > Disciplined Source 
> > 
> > 
> > Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not
> > one of the better GPS units based on what Paul mentioned.  But I think
> > there is software out there that will let me at least monitor what my
> > unit is doing and how many birds it is receiving data from.
> > 
> > Ublox makes excellent receivers. The monitoring software is fine.
> > 
> > https://www.u-blox.com/en/product/u-center-windows
> > 
> > But they dont talk (old) scpi.
> > 
> > --
> >  Björn
> > ___
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> 
> -- 
> WBW,
> 
> V.P.
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[time-nuts] Symmetricom SA.35M Information Request

[Ed Palmer]

Does anyone have any info on the Symmetricom SA.35M Miniature Rb 
Standard?  I have the data sheet, patent document and the MACDEMO 
program.  Is there anything else available?  For example, I'd like some 
more explanation of the various parameters read by the MACDEMO program.


I have a sick unit that I'm exploring.  It won't lock.  The VCXO is 
sweeping and I've confirmed the presence of the 6.834 GHz RF signal so 
I'm now looking towards the laser.


I don't expect that I'll be able to get it working, but it's fun to play 
with.


Ed

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Re: [time-nuts] BG7TBL GPS Disciplined Source

[John Miles]

My understanding from someone who has purchased one recently is that the 
frequency offset error was indeed just a bug, and that it's now fixed.  I've 
added a note to the end of my page at http://www.ke5fx.com/gpscomp.htm to that 
effect.

If the bug has been fixed (or the algorithm replaced), and if you get one with 
a good MV89A OCXO, the BG7TBL GPSDO has the potential for decent performance.  
In principle all of the right ingredients are there... it's just a question of 
whether the software is making the most of them.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Lars
> Walenius
> Sent: Monday, March 14, 2016 12:41 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] BG7TBL GPS Disciplined Source
> 
> Hi
> 
> If you are lucky the MV89 might be a very good OCXO and U-Blox makes very
> good GPS modules. The NEO-6M is not the best as it isn´t a timing module. But
> in your GPSDO the GPS module with an external antenna is not the limiting
> factor but more the controller and it´s limited resolution on the time
> measurement that is larger than the ripple from the GPS module. Also the
> software with FLL seems to limit the performance a lot. But with the long time
> constant the frequency accuracy, even with the offset due to the FLL, will be
> quite good.
> 
> U-blox own software uCenter have worked well for me.
> 
> Lars

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Re: [time-nuts] HP 5065A repair

[Bob Camp]

Hi

Yes, fat fingers strike yet again …



I have never seen data on a 5065 run in an altitude chamber. I’ve done the 
measurements on OCXO’s and may try it on some of the little telecom Rb’s. For 
small items, it’s a pretty easy test to run. For bigger things, the “pressure 
vessel” gets a bit harder to lash up. The fiddly part is keeping the 
temperature constant as the pressure zooms up and down. 

Bob

> On Mar 14, 2016, at 3:20 PM, Lars Walenius  wrote:
> 
> Hi
> 
> Shouldn´t 5x10^-11 over 50C be 1x10^-12 / C? So with 2-4°C variation it is 
> 2-4x10^-12.
> 
> What about pressure variations for the HP5065 and other Rb´s? My LPRO have 
> about 7x10^-14/mBar (hPa) so with 15-20mbar change, that can happen quite 
> quick, it is also in the ^-12 range. The tempco for my LPRO is 7x10^-13/°C 
> and drift in the high ^-14 per day so my GPSDO controller mostly fights the 
> temperature and pressure variations I think. I like having a GPS disciplined 
> Rb as I haven´t had to adjust it during the last years. Of course a OCXO 
> based GPSDO will also stay on frequency. For me the Rb have been good when I 
> have tested GPS modules and GPSDO´s just out of curiosity. In hold mode it 
> have been useful to get the ADEV out to say 1 secs (low ^-13).
> 
> Lars
> 
> Från: Bob Camp
> Skickat: den 14 mars 2016 02:01
> Till: Discussion of precise time and frequency 
> measurement
> Ämne: Re: [time-nuts] HP 5065A repair
> 
> Hi
> 
> Some math:
> 
> 5x10^-11 over 50C
> 
> You have 1x10^-13 / C
> 
> If you have pretty good HVAC you get 2C cycles. On a typical home system, you 
> get 2X that or more.
> 
> Net is a bump at 2x10^-13 (or more).
> 
> That assumes no hysteresis. (Hint: there always is hysteresis).
> 
> That assumes you have no rate dependent effects. (… they almost always are 
> present ..).
> 
> If you are at 10X the data sheet level, the bump is more like 2x10^-12 (or 
> more). Either one will likely show up on a good test plot.
> 
> Can you take care of all this? Of course you can. Does modeling and 
> correcting all this fall into the “quick and easy fix” category? Nope, not at 
> all. The thread is about a request for a simple approach to an Rb setup. That 
> sort of thing does not include fancy models and all sorts of corrections.
> 
> Bob
> 
> 
> 
>> On Mar 13, 2016, at 5:10 PM, Poul-Henning Kamp  wrote:
>> 
>> 
>> In message , cdel...@juno.com 
>> writes:
>> 
>>> As far a tempco goes, unless your lab swings tens of degrees will you
>>> really see it?
>> 
>> Well, I do...
>> 
>> My air-con is far from optimal, but it clearly makes a very obvious
>> bump in my AVAR plots.
>> 
>> 
>> --
>> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>> p...@freebsd.org | TCP/IP since RFC 956
>> FreeBSD committer   | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Bob Camp]

Hi

It’s not just a Russian OCXO, it’s a Russian OCXO that has been through a very 
nasty salvage process. It is rare to find one that is in very good shape after 
the “gentle hands” have removed it from the original equipment. 

Bob

> On Mar 14, 2016, at 2:52 PM, Gedas  wrote:
> 
> Hi Hal, and TU for the reply. Tu also to everyone else with the very helpful 
> hints and info.  Following the advice of Joe I checked out the EEV Blog 
> site.very good information about the different variants of this maker.  
> Turns out, because I have a model (date code) of 2014-12-09 that it 
> corresponds to this revision and information:
> 
> custom board with surplus russianmorion mv89 
> OCXO. gps isu-blox 
> NEO-6M-0-001 .
> 
> Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not one of 
> the better GPS units based on what Paul mentioned.  But I think there is 
> software out there that will let me at least monitor what my unit is doing 
> and how many birds it is receiving data from. I also have the 8-port signal 
> splitter which is nice as I can now run my reference to all my various TE.
> 
> Oh well, it is what it is as I do not have the money to purchase a different 
> one. To answer your question I am using the supplied "hockey puck" style 
> antenna placed outside my basement window well, sitting on a small wooden 
> shelf, but close to ground level.  The antenna should have a clear view from 
> 90-280 degrees, from an elevation angle of 0-90 degrees.  Anything from West 
> to North to East (~280-90 degrees) is blocked by the house.  I guess my next 
> step, as Bob suggested will be to install some monitoring software to see how 
> many birds I am able to see on average.
> 
> Gedas, W8BYA
> 
> Gallery at http://w8bya.com
> Light travels faster than sound
> This is why some people appear bright until you hear them speak.
> 
> On 3/14/2016 12:55 AM, Hal Murray wrote:
>> w8...@mchsi.com said:
>>> This is where I really embarrass myself.sometime ago I purchased an
>>> inexpensive 10 MHz GPS based reference source (BG7TBL GPS Disciplined
>>> Source) for my various counters, transceivers, spectrum analyzers, etc  and
>>> was wondering if it was a good purchase and if anyone else used a  similar
>>> unit.  I guess in the end I am curious to know what the short &  long term
>>> accuracy and stability of my unit may be?  I no longer have  access to any
>>> accurate (known) frequency sources like I did while  employed and I do not
>>> think I have the equipment here at home to measure  my unit myself.
>> Long term accuracy will be very good - you are tracking GPS.
>> 
>> You didn't say anything about your antenna.  That's probably the major
>> contributor to your short term accuracy.
>> 
>> Google found:
>>   http://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
>> Looks like there are various versions.
>> 
>> 
> 
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Paul]

On Mon, Mar 14, 2016 at 2:52 PM, Gedas  wrote:

> And, I guess the U-Blox is not one of the better GPS units based on what
> Paul mentioned


Actually the U-Blox receivers are perfectly fine.  The problem with these
units (as far as I can tell) is that you don't have any control over the
GPS (which is what I failed to make clear earlier) unless you can reverse
engineer the set-up code.  The serial port data on mine is transmit only.
Because of this I can't select the output strings or their format.  The
unit I have does emit the sats-in-view message but it's U-Blox binary (aka
UBX) not NMEA ascii which makes it a bit more difficult to parse.
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Vlad]

I would say its even more convenient to monitor binary format, since its 
more compact and could be read as a structures


// u-blox UBX protocol essentials

typedef struct ubx_header {
unsigned char preamble1;
unsigned char preamble2;
unsigned char msg_class;
unsigned char msg_id;
unsigned short length;
} my_ubx_header;

typedef struct ubx_nav_timegps {
unsigned long iTOW_ms;
signed long fTOW_ns;
signed short week;
signed char leapS;
unsigned char valid;
unsigned long tAcc;
} my_ubx_nav_timegps;

typedef struct ubx_nav_timeutc {
unsigned long iTOW_ms;
unsigned long tAcc_ns;
signed long nano;
unsigned short year;
unsigned char month;
unsigned char day;
unsigned char hour;
unsigned char min;
unsigned char sec;
unsigned char valid;
} my_ubx_nav_timeutc;

and so on...


On 2016-03-14 15:38, Björn wrote:

 Originalmeddelande Från: Gedas
 Datum:2016-03-14  19:52  (GMT+01:00)
Till: Discussion of precise time and frequency measurement
 Rubrik: Re: [time-nuts] BG7TBL GPS
Disciplined Source 


Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not
one of the better GPS units based on what Paul mentioned.  But I think
there is software out there that will let me at least monitor what my
unit is doing and how many birds it is receiving data from.

Ublox makes excellent receivers. The monitoring software is fine.

https://www.u-blox.com/en/product/u-center-windows

But they dont talk (old) scpi.

--
 Björn
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--
WBW,

V.P.
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Re: [time-nuts] Conditioning Rubidium Oscillators

[Bob Camp]

Hi

Yes indeed, the ionosphere is *not* predictable day to day so no matter what 
you saw yesterday, today will be different. Tomorrow likely will be different 
as well. Two bumps a day (at least) and even during the day they aren’t certain 
to be the same. 

Since it is a “space weather” determined thing, with L1 only, all you can do is 
guess at confidence levels. The real answer is to go to L1/L2 or L1/L2/L5 and 
at least reduce the level of the problem. You can also do some coordinated 
things at L1, but then you no longer have a stand alone device. You are part of 
a network and reliant on a data flow from it.  You are also dependent on that 
network’s data being more accurate than the item you are trying to discipline. 

Bob

> On Mar 14, 2016, at 2:37 PM, Lars Walenius  wrote:
> 
> I read this but couldn´t understand why this is superior to the PI-loop with 
> a pre-filter?
> 
> http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Control-%E2%80%93-A-Different-Approach.pdf
> 
> Anybody can say why? Even if regression is very useful the limitation of the 
> GPS and ionosphere will be the problem?How much better is it reasonable to 
> get??
> 
> Lars
> 
> 
> Från: GandalfG8--- via time-nuts
> Skickat: den 3 mars 2016 22:00
> Till: time-nuts@febo.com
> Ämne: [time-nuts] Conditioning Rubidium Oscillators
> 
> I'm sure I won't be the only one receiving newsletters from Precise  Time
> and Frequency Inc, but I thought it worth mentioning their latest  white
> paper as it offers some thoughts on the conditioning of  rubidium standards 
> via
> RS232 control.
> 
> "Rubidium Control - A Different Approach" can be found here
> 
> http://ptfinc.com/resources/
> 
> A very basic registration is required but I've always found their mailings
> to be interesting and informative whilst never being intrusive, and
> there's always an unsubscribe option anyway.
> 
> Please not that I have no affiliation whatsoever, just passing on something
> I found interesting.
> 
> Regards
> 
> Nigel
> GM8PZR
> 
> 
> 
> 
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Lars Walenius]

Hi

If you are lucky the MV89 might be a very good OCXO and U-Blox makes very good 
GPS modules. The NEO-6M is not the best as it isn´t a timing module. But in 
your GPSDO the GPS module with an external antenna is not the limiting factor 
but more the controller and it´s limited resolution on the time measurement 
that is larger than the ripple from the GPS module. Also the software with FLL 
seems to limit the performance a lot. But with the long time constant the 
frequency accuracy, even with the offset due to the FLL, will be quite good.

U-blox own software uCenter have worked well for me.

Lars

Från: Gedas
Skickat: den 14 mars 2016 20:00
Till: Discussion of precise time and frequency 
measurement
Ämne: Re: [time-nuts] BG7TBL GPS Disciplined Source

Hi Hal, and TU for the reply. Tu also to everyone else with the very
helpful hints and info.  Following the advice of Joe I checked out the
EEV Blog site.very good information about the different variants of
this maker.  Turns out, because I have a model (date code) of 2014-12-09
that it corresponds to this revision and information:

custom board with surplus russianmorion mv89
OCXO. gps isu-blox
NEO-6M-0-001 .

Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not
one of the better GPS units based on what Paul mentioned.  But I think
there is software out there that will let me at least monitor what my
unit is doing and how many birds it is receiving data from. I also have
the 8-port signal splitter which is nice as I can now run my reference
to all my various TE.

Oh well, it is what it is as I do not have the money to purchase a
different one. To answer your question I am using the supplied "hockey
puck" style antenna placed outside my basement window well, sitting on a
small wooden shelf, but close to ground level.  The antenna should have
a clear view from 90-280 degrees, from an elevation angle of 0-90
degrees.  Anything from West to North to East (~280-90 degrees) is
blocked by the house.  I guess my next step, as Bob suggested will be to
install some monitoring software to see how many birds I am able to see
on average.

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound
This is why some people appear bright until you hear them speak.

On 3/14/2016 12:55 AM, Hal Murray wrote:
> w8...@mchsi.com said:
>> This is where I really embarrass myself.sometime ago I purchased an
>> inexpensive 10 MHz GPS based reference source (BG7TBL GPS Disciplined
>> Source) for my various counters, transceivers, spectrum analyzers, etc  and
>> was wondering if it was a good purchase and if anyone else used a  similar
>> unit.  I guess in the end I am curious to know what the short &  long term
>> accuracy and stability of my unit may be?  I no longer have  access to any
>> accurate (known) frequency sources like I did while  employed and I do not
>> think I have the equipment here at home to measure  my unit myself.
> Long term accuracy will be very good - you are tracking GPS.
>
> You didn't say anything about your antenna.  That's probably the major
> contributor to your short term accuracy.
>
> Google found:
>http://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
> Looks like there are various versions.
>
>

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Re: [time-nuts] HP 5065A repair

[Lars Walenius]

Hi

Shouldn´t 5x10^-11 over 50C be 1x10^-12 / C? So with 2-4°C variation it is 
2-4x10^-12.

What about pressure variations for the HP5065 and other Rb´s? My LPRO have 
about 7x10^-14/mBar (hPa) so with 15-20mbar change, that can happen quite 
quick, it is also in the ^-12 range. The tempco for my LPRO is 7x10^-13/°C and 
drift in the high ^-14 per day so my GPSDO controller mostly fights the 
temperature and pressure variations I think. I like having a GPS disciplined Rb 
as I haven´t had to adjust it during the last years. Of course a OCXO based 
GPSDO will also stay on frequency. For me the Rb have been good when I have 
tested GPS modules and GPSDO´s just out of curiosity. In hold mode it have been 
useful to get the ADEV out to say 1 secs (low ^-13).

Lars

Från: Bob Camp
Skickat: den 14 mars 2016 02:01
Till: Discussion of precise time and frequency 
measurement
Ämne: Re: [time-nuts] HP 5065A repair

Hi

Some math:

5x10^-11 over 50C

You have 1x10^-13 / C

If you have pretty good HVAC you get 2C cycles. On a typical home system, you 
get 2X that or more.

Net is a bump at 2x10^-13 (or more).

That assumes no hysteresis. (Hint: there always is hysteresis).

That assumes you have no rate dependent effects. (… they almost always are 
present ..).

If you are at 10X the data sheet level, the bump is more like 2x10^-12 (or 
more). Either one will likely show up on a good test plot.

Can you take care of all this? Of course you can. Does modeling and correcting 
all this fall into the “quick and easy fix” category? Nope, not at all. The 
thread is about a request for a simple approach to an Rb setup. That sort of 
thing does not include fancy models and all sorts of corrections.

Bob



> On Mar 13, 2016, at 5:10 PM, Poul-Henning Kamp  wrote:
>
> 
> In message , cdel...@juno.com writes:
>
>> As far a tempco goes, unless your lab swings tens of degrees will you
>> really see it?
>
> Well, I do...
>
> My air-con is far from optimal, but it clearly makes a very obvious
> bump in my AVAR plots.
>
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Björn]

 Originalmeddelande Från: Gedas 
 Datum:2016-03-14  19:52  (GMT+01:00) 
Till: Discussion of precise time and frequency measurement 
 Rubrik: Re: [time-nuts] BG7TBL GPS Disciplined 
Source 


Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not 
one of the better GPS units based on what Paul mentioned.  But I think 
there is software out there that will let me at least monitor what my 
unit is doing and how many birds it is receiving data from. 

Ublox makes excellent receivers. The monitoring software is fine.

https://www.u-blox.com/en/product/u-center-windows

But they dont talk (old) scpi.

--
 Björn
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[time-nuts] BG7TBL GPS Disciplined Source

[Mark Sims]

I believe that it was mentioned here that the BG7TBL GPSDO disciplined 
oscillator controls the OCXO using a FLL (frequency locked loop) instead of a 
PLL (phase locked loop).  Their implementation causes a slight error in the 
output frequency.  Search the time-nuts archives (best to use Google) for the 
relevant thread(s).

  
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Gedas]

Hi Hal, and TU for the reply. Tu also to everyone else with the very 
helpful hints and info.  Following the advice of Joe I checked out the 
EEV Blog site.very good information about the different variants of 
this maker.  Turns out, because I have a model (date code) of 2014-12-09 
that it corresponds to this revision and information:


custom board with surplus russianmorion mv89 
OCXO. gps isu-blox 
NEO-6M-0-001 .


Who would have guessed a Russian OCXO.  And, I guess the U-Blox is not 
one of the better GPS units based on what Paul mentioned.  But I think 
there is software out there that will let me at least monitor what my 
unit is doing and how many birds it is receiving data from. I also have 
the 8-port signal splitter which is nice as I can now run my reference 
to all my various TE.


Oh well, it is what it is as I do not have the money to purchase a 
different one. To answer your question I am using the supplied "hockey 
puck" style antenna placed outside my basement window well, sitting on a 
small wooden shelf, but close to ground level.  The antenna should have 
a clear view from 90-280 degrees, from an elevation angle of 0-90 
degrees.  Anything from West to North to East (~280-90 degrees) is 
blocked by the house.  I guess my next step, as Bob suggested will be to 
install some monitoring software to see how many birds I am able to see 
on average.


Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound
This is why some people appear bright until you hear them speak.

On 3/14/2016 12:55 AM, Hal Murray wrote:

w8...@mchsi.com said:

This is where I really embarrass myself.sometime ago I purchased an
inexpensive 10 MHz GPS based reference source (BG7TBL GPS Disciplined
Source) for my various counters, transceivers, spectrum analyzers, etc  and
was wondering if it was a good purchase and if anyone else used a  similar
unit.  I guess in the end I am curious to know what the short &  long term
accuracy and stability of my unit may be?  I no longer have  access to any
accurate (known) frequency sources like I did while  employed and I do not
think I have the equipment here at home to measure  my unit myself.

Long term accuracy will be very good - you are tracking GPS.

You didn't say anything about your antenna.  That's probably the major
contributor to your short term accuracy.

Google found:
   http://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
Looks like there are various versions.




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Re: [time-nuts] Conditioning Rubidium Oscillators

[Lars Walenius]

I read this but couldn´t understand why this is superior to the PI-loop with a 
pre-filter?

http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Control-%E2%80%93-A-Different-Approach.pdf

Anybody can say why? Even if regression is very useful the limitation of the 
GPS and ionosphere will be the problem?How much better is it reasonable to get??

Lars


Från: GandalfG8--- via time-nuts
Skickat: den 3 mars 2016 22:00
Till: time-nuts@febo.com
Ämne: [time-nuts] Conditioning Rubidium Oscillators

I'm sure I won't be the only one receiving newsletters from Precise  Time
and Frequency Inc, but I thought it worth mentioning their latest  white
paper as it offers some thoughts on the conditioning of  rubidium standards via
RS232 control.

"Rubidium Control - A Different Approach" can be found here

http://ptfinc.com/resources/

A very basic registration is required but I've always found their mailings
to be interesting and informative whilst never being intrusive, and
there's always an unsubscribe option anyway.

Please not that I have no affiliation whatsoever, just passing on something
 I found interesting.

Regards

Nigel
GM8PZR




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Re: [time-nuts] When does NIST change to DST?

[Nick Sayer via time-nuts]

Well, then my clock (and perhaps others) is being lazy about interpreting the 
bits. If it looks at the left bit only, then that would explain early 
transitions. The other possibility is misreading the right hand bit as being a 
1 during one reading and deciding that it had “missed” the change somehow.

> On Mar 13, 2016, at 9:38 PM, Tom Van Baak  wrote:
> 
> Hi Andy,
> 
> No, there's nothing about 0200Z. Correct, WWVB doesn't know your local zone.
> 
> WWVB itself doesn't "switch" to/from DST. It always only transmits UTC. It is 
> up to your receiver-clock to translate UTC to local time for the user 
> display. This is why most of WWVB radio controlled clocks have a little PMCE 
> (Pacific / Mountain / Central / Eastern) switch.
> 
> The WWVB data format also includes bits which announce if DST change will 
> occur. It is up to the receiver-clock to decode these bits and make the 1 
> hour adjustment at the appropriate time (usually 2 am local time).
> 
> See also:
> https://en.wikipedia.org/wiki/WWVB
> http://tf.nist.gov/general/pdf/2422.pdf
> http://www.nist.gov/pml/div688/grp40/radioclocks.cfm
> 
> /tvb
> 
> - Original Message - 
> From: "Andy" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Sunday, March 13, 2016 7:21 PM
> Subject: Re: [time-nuts] When does NIST change to DST?
> 
> 
>> I wonder if WWVB switches to DST around 0200Z, maybe?  Since it can't
>> tell where your local zone is.
>> 
>> Andy
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Paul]

On Sun, Mar 13, 2016 at 11:47 PM, Gedas  wrote:

> sometime ago I purchased an inexpensive 10 MHz GPS based reference source
> (BG7TBL GPS Disciplined Source) for my various counters, transceivers,
> spectrum analyzers, etc and was wondering if it was a good purchase


It was probably an acceptable purchase.  Hopefully you didn't get one with
a U-Blox GPS since monitoring U-Blox binary output is unpleasant.  If you
feel like doing a bit of fiddling Jackson Labs makes some nice products and
are quite time-nut friendly.  Back in 2014 they did a cost-effective
(<$200)  board which might still be available at time-nuts pricing.  Of
course the BG7 units should come with a nice ovenized oscillator in a
reasonable chassis which are "add-ons" with the JL board.
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Re: [time-nuts] When does NIST change to DST?

[Bob Camp]

HI

Most WWVB clocks are unable to pick up a signal continuously. The signal to 
noise simply isn’t good enough 24 hours a day. Because of this (and power 
considerations) they do a check or three in the middle of the night and go back 
to sleep. If they sync up, fine. If they don’t, try again tomorrow. That 
approach works fine most of the time. When it gets close to a time shift, you 
notice the process a lot more. My wife’s watch is not as good picking up WWVB 
as the rest of the stuff here. I can pretty reliably predict that I will hear 
about that twice a year ….oddly enough, I can also predict the dates when I 
will hear about it ;)

Bob

> On Mar 14, 2016, at 12:38 AM, Tom Van Baak  wrote:
> 
> Hi Andy,
> 
> No, there's nothing about 0200Z. Correct, WWVB doesn't know your local zone.
> 
> WWVB itself doesn't "switch" to/from DST. It always only transmits UTC. It is 
> up to your receiver-clock to translate UTC to local time for the user 
> display. This is why most of WWVB radio controlled clocks have a little PMCE 
> (Pacific / Mountain / Central / Eastern) switch.
> 
> The WWVB data format also includes bits which announce if DST change will 
> occur. It is up to the receiver-clock to decode these bits and make the 1 
> hour adjustment at the appropriate time (usually 2 am local time).
> 
> See also:
> https://en.wikipedia.org/wiki/WWVB
> http://tf.nist.gov/general/pdf/2422.pdf
> http://www.nist.gov/pml/div688/grp40/radioclocks.cfm
> 
> /tvb
> 
> - Original Message - 
> From: "Andy" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Sunday, March 13, 2016 7:21 PM
> Subject: Re: [time-nuts] When does NIST change to DST?
> 
> 
>> I wonder if WWVB switches to DST around 0200Z, maybe?  Since it can't
>> tell where your local zone is.
>> 
>> Andy
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Bob Camp]

Hi

The key to any GPSDO is continuous satellite view. A good antenna should give 
you at least 4 satellites in view / locked on at all times. Much of the time 
you should see more than 8 satellites. Set up with whatever software your 
device uses and have it run long term plots of the satellites in view. The next 
step is to monitor DAC voltage and see what it’s doing. 

The monitoring software is a very key part of any GPSDO setup. It’s not easy 
stuff to write and it can be fairly device specific. One advantage of the 
surplus commercial units is the availability of multiple versions of monitoring 
software for them. You may have to dig a bit more for the BG7TBL units. They 
are a bit new on the market. 

Bob


> On Mar 13, 2016, at 11:47 PM, Gedas  wrote:
> 
> Hello to the group. I am a new member and 1st wanted to say hello. I also 
> wanted to say that I have been reading, with great interest, most of the 
> posts here for the last 2-3 weeks.  I must say, I am quite ignorant of the 
> majority of the information & terms being passed back and forth so this is a 
> neat learning experience for me. I am a retired EE (had a prior life in the 
> TEMPEST community for over 30 years) and I am slowly assembling my collection 
> of test equipment here at home, purely for fun.
> 
> This is where I really embarrass myself.sometime ago I purchased an 
> inexpensive 10 MHz GPS based reference source (BG7TBL GPS Disciplined Source) 
> for my various counters, transceivers, spectrum analyzers, etc and was 
> wondering if it was a good purchase and if anyone else used a similar unit.  
> I guess in the end I am curious to know what the short & long term accuracy 
> and stability of my unit may be?  I no longer have access to any accurate 
> (known) frequency sources like I did while employed and I do not think I have 
> the equipment here at home to measure my unit myself.
> 
> Gedas, W8BYA
> 
> Gallery at http://w8bya.com
> Light travels faster than sound
> This is why some people appear bright until you hear them speak.
> 
> 
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Re: [time-nuts] BG7TBL GPS Disciplined Source

[Hal Murray]

w8...@mchsi.com said:
> This is where I really embarrass myself.sometime ago I purchased an
> inexpensive 10 MHz GPS based reference source (BG7TBL GPS Disciplined
> Source) for my various counters, transceivers, spectrum analyzers, etc  and
> was wondering if it was a good purchase and if anyone else used a  similar
> unit.  I guess in the end I am curious to know what the short &  long term
> accuracy and stability of my unit may be?  I no longer have  access to any
> accurate (known) frequency sources like I did while  employed and I do not
> think I have the equipment here at home to measure  my unit myself. 

Long term accuracy will be very good - you are tracking GPS.

You didn't say anything about your antenna.  That's probably the major 
contributor to your short term accuracy.

Google found:
  http://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
Looks like there are various versions.


-- 
These are my opinions.  I hate spam.



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