Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Bruce Griffiths]

michael taylor wrote:
> You have made similar comments about I believe the same approach in
> the past. I was wondering if you have ever sketched out a schematic,
> even if only rough. Perhaps with a few suggested components to try
> (i.e. DAC, Op-Amp) that would be a good starting point for anyone who
> wanted to prototype and evaluate the performance of this approach.
>
> It is beyond my elementary design abilities to convert your
> description into a well implemented design on my own, but I would be
> interested in try to at least see if I could construct an unit using
> these suggested techniques.
>
> -Michael
>   

Michael

The analog circuitry for a sigma-delta DAC is attached.
The input is optically isolated using a high speed low jitter CMOS
optocoupler (Avago produce an equivalent device) to break low frequency
ground loops.
Similarly an RF transformer should be used to couple the OCXO output to
the Digital board breaking another potential low frequency ground loop.
The task of the microprocessor firmware is to generate the delta sigma 1
bit input data for the optocoupler.

Alternatively one of Analog devices chip scale transformer isolators
could be used.

Bruce


SigmaDeltaEFCDAC.pdf
Description: Adobe PDF document
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[bg]

On Tue, 2007-12-11 at 18:38 -0500, John Ackermann N8UR wrote:

> To get decent (for some definition of "decent") timing, you need to
> operate the receiver in "0-D" mode, telling it where it is and letting
> it solve just for time.  I haven't done the experiments myself but I
> believe that the time accuracy is pretty dramatically degraded when
> operating in 2-D or 3-D mode.
> 
> > How long does a survey take (in good conditions) and what sort of time 
> > constant would you want to use with a navigation box?
> 
> It depends on the receiver, but usually it's a few hours to a full day.
>  Of course, if you use external software you can use whatever time
> period you want.
> 
> John

I am surprised surveying mode is needed anymore. In a SA environment it
makes sense, but for me its hard to understand with the current accuracy
given by the GPS system.

--

   Björn


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Using a Vectron OCXO 5mhz oscilator with ntpd

[michael taylor]

On Dec 11, 2007 11:19 PM, Todd Eddy <[EMAIL PROTECTED]> wrote:
>
> My thought was using the ntp servers for that, since that will get the
> signal withing a couple msecs of the time, then use the pps output to
> get it even more accurate from there.  Kinda like one of the ways to
> interface with the gps receiver that it only gets the PPS signal and not
> the time.  Kinda ugly, but you got to start somewhere.  I'll probably
> end up getting a gps receiver since there's lots of documentation on
> that and I can mess with it at home, or maybe convince work to let me
> drill a hole in the roof :)  Thanks the much simpler diagram though.

For the accuracy of a NTP public server, using a TAPR Clock Block (or
RefLock II, www.tapr.org)  with a OCXO or TCXO is likely as much
modification as may be usefully necessary for a public
(Internet-facing) NTP server. I'm not sure of how much accuracy and/or
precision you care about. Is to within 2 milliseconds good enough?

See:  John Ackermann's "Is This the World's Most Accurate NTP Server
Hardware?" 

I'd consider getting a Timing GPS receiver such as the iLotus "M12M
Timing", available from Synergy Systems, or the Trimble "Resolution T"
module. If only for your "house reference" to evaluate your attempts.
Older Motorola OnCore GPS modules are often cheap on eBay, look for
the timing versions.

-Michael

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[SAIDJACK]

 
In a message dated 12/11/2007 21:06:12 Pacific Standard Time,  
[EMAIL PROTECTED] writes:

>At  night?
>Or do you have a very long  lead?

>Bruce


Used to charge the Pb during the day. 30 Watt GE array = $125 at:
 
_http://sunelec.com/_ (http://sunelec.com/) 
 
That will at least significantly extend the battery run time.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[Bruce Griffiths]

[EMAIL PROTECTED] wrote:
>  
> In a message dated 12/11/2007 19:08:14 Pacific Standard Time, [EMAIL 
> PROTECTED]  
> writes:
>
>   
>> I  think the situation is somewhat better than that.  I'm looking at my  
>> LPRO-101.  It's about 18-watts while warming up, but once the  physics 
>> package is up to temp and locked, the power consumption drops  to about 
>> 5-watts.  The larger rubidium modules are probably more  power hungry, 
>> but the small onces aren't so bad once they are  running.  You still 
>> might need a trunk full of batteries  though...
>> 
>
>   
>> jeff
>> 
>
>
>
> Hi Jeff,
>  
> you are right. My PRS10 is rated at 13W steady state at room temp. 5W is  
> pretty good. Solar array's are probably the best solution.
>  
> bye,
> Said
>
>
>
>   
At night?
Or do you have a very long lead?

Bruce


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[SAIDJACK]

 
In a message dated 12/11/2007 19:08:14 Pacific Standard Time, [EMAIL PROTECTED] 
 
writes:

>I  think the situation is somewhat better than that.  I'm looking at my  
>LPRO-101.  It's about 18-watts while warming up, but once the  physics 
>package is up to temp and locked, the power consumption drops  to about 
>5-watts.  The larger rubidium modules are probably more  power hungry, 
>but the small onces aren't so bad once they are  running.  You still 
>might need a trunk full of batteries  though...

>jeff



Hi Jeff,
 
you are right. My PRS10 is rated at 13W steady state at room temp. 5W is  
pretty good. Solar array's are probably the best solution.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[Rex]

> You still 
> might need a trunk full of batteries though...
>
> jeff
>   
As a ham, I've got a vehicle with a bunch of batteries and they charge 
off of my engine, but let's be practical. I'd rather spend my battery's 
energy on long term receiving and on transmitting significant power than 
on feeding a rubidium or such. Of course, in that vein, I believe my 
lower power timing solution is adequate to get me making contacts on the 
frequency. As per my other post tonight, I think a good ocxo is.

TVB, in his story, implied some of the challenges of feeding three 
Cesium standards for several days inside of his vehicle. More details 
would be interesting  in what he used.

Hmm. Another topic for discussion. Power consumption vs good or better 
time-nuts performance. Has this been discussed? If not let's start a new 
thread.





___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Using a Vectron OCXO 5mhz oscilator with ntpd

[Todd Eddy]

Bruce Griffiths wrote:
> 
> The first clock shaper is about the simplest reasonably high performance
> clock shaper that can be devised.
> However your application doesnt actually require a particularly high
> performance clock shaper, you could use an inverting gate with a
> resistor connected between its input and output plus a capacitor to
> couple the sinewave into its input as illustrated in the attached
> schematic. Its difficult to get much simpler than this.

It was the inverting gate that was throwing me off as I've never come
across it before. After doing a lot more searching and realizing what
exactly that inverting gate does the circuit makes a lot more sense now.

> 
> By itself, even dividing down a 5MHz crystal to produce a PPS output
> (which could be used to sync an ntp) isnt a great deal of use without a
> means of syncing the generated PPS output to UTC.
> You could use the 5MHz signal together with a small synthesizer board to
> replace the crystal on the PC motherboard, however all this does is
> improve the stability of the PC  timebase. You still have the
> synchronisation problem.

My thought was using the ntp servers for that, since that will get the
signal withing a couple msecs of the time, then use the pps output to
get it even more accurate from there.  Kinda like one of the ways to
interface with the gps receiver that it only gets the PPS signal and not
the time.  Kinda ugly, but you got to start somewhere.  I'll probably
end up getting a gps receiver since there's lots of documentation on
that and I can mess with it at home, or maybe convince work to let me
drill a hole in the roof :)  Thanks the much simpler diagram though.

> 
> If you are really new to electronics then it would be better to buy an
> already debugged  system, there are no shortcuts  to learning sufficient
> about electronics, you have to read the books and build /debug real
> circuits.
> 
> Bruce
> 
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



smime.p7s
Description: S/MIME Cryptographic Signature
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Power consumption

[Bruce Griffiths]

Rex wrote:
>> You still 
>> might need a trunk full of batteries though...
>>
>> jeff
>>   
>> 
> As a ham, I've got a vehicle with a bunch of batteries and they charge 
> off of my engine, but let's be practical. I'd rather spend my battery's 
> energy on long term receiving and on transmitting significant power than 
> on feeding a rubidium or such. Of course, in that vein, I believe my 
> lower power timing solution is adequate to get me making contacts on the 
> frequency. As per my other post tonight, I think a good ocxo is.
>
> TVB, in his story, implied some of the challenges of feeding three 
> Cesium standards for several days inside of his vehicle. More details 
> would be interesting  in what he used.
>
> Hmm. Another topic for discussion. Power consumption vs good or better 
> time-nuts performance. Has this been discussed? If not let's start a new 
> thread.
>   
Rex

Would it not be best to collect the relevant performance and power
consumption data for known solutions and summarise it in the form of a
table/spreadsheet or similar?
This could then serve as a baseline for new designs/suggestions.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Rex]

Eric Fort wrote:
> I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
> reference (probably quartz based) with enough stability over a period
> of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
> within 100hz  while mountaintop contesting.  Suggestions are
> appreciated.  something that is small and ran off 12 volts dc (car
> battery) would be a definite plus.
>
> Thanks,
>
> Eric
>   
100 Hz accuracy at 47 GHz is a nice goal but probably hardly necessary 
in practice.

What needs to be sought to make contacts on upper microwave frequencies 
is minimizing ALL the uncertainties. The main thing most hams short-cut  
is aiming accuracy. You really need an accurate aiming degree gauge and 
a way to calibrate it to your current operating position. Here in sunny 
California I usually use the sun shadow on my dish, some software on my 
Palm handheld, and a setting of the time on the Palm to a second or two 
to do the aiming calibration of my tripod. If the sun is not clearly 
available, beacons can be used with great accuracy if available. A 
compass can help too, but I think that it is the hardest to get 
accurate. Knowing up and down angles vs horizontal is helpful too.

For frequency I have used a decent crystal OCXO for some years on 10 
GHz. I'm sure it would be fine on 24 GHz or even higher. I just recently 
made my first contact on 47 GHz with a good, but much less accurate, 
reference. I have a friend who has taken out a very nice 10/24 GHz rig 
with his frequency based on a rubidium source. We shared an operation 
spot one day and while talking with him I said I thought that I couldn't 
justify a rubidium vs. my simple decent OCXO for two days of operation. 
There's the battery current consumption and any good xtal's drift over 
this relatively short period is probably too small to really matter in 
finding the average station and making the contact. He agreed.

If you are going for the record contact that cannot even be heard with 
the naked ear, then, yes, it may be helpful to have the resolution 
provided by an atomic source or GPS enhanced receiver. A good xtal-based 
source seems to be the way to go for phase noise if that is important 
and for ham activities that is important.

My thought was to own a decent GPS disciplined source based on a good  
xtal  source. My  search obtained a Z3816A that I picked up a few years 
ago. That is my main local reference. I also have a few rubidium sources 
that I have picked up but haven't yet accurately synced all of them to 
my best reference.

As the time-nuts list influences me, I'll do more to get all my sources 
close to my best reference and then maybe do more to see how they 
compare, but for my ham activities over a weekend, a good OCXO that has 
been set accurately is quite adequate.

The time-nuts list is a great place to learn about all sorts of stuff 
including test equipment. I intend to hang around and learn, even if I 
never push the envelope nearly as far as many here are focused on.




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[SAIDJACK]

 
In a message dated 12/11/2007 13:14:14 Pacific Standard Time,  
[EMAIL PROTECTED] writes:

>Why  not lock it to a GPS timing receiver output when its at home, and
>allow  the controller to learn the aging and tempco characteristics etc
>of the  oscillator being disciplined and use this information to correct
>for  temperature variations etc at the remote site?

>The model used can  be as complex as required to achieve the desired
>performance and a PC  can be used to derive optimum correction
>coefficients, the micro only  has to perform the simpler task of applying
>these  corrections.

>Bruce




Hi Bruce,
 
the problem with that is that OCXO retrace can really suck.
 
Some common OCXO's have parts in E-09 and even worse retrace.
 
Doing about 10 minutes of Auto Survey on an M12+ receiver and OCXO warmup,  
followed by about 20 minutes of active GPS locking will get you much better  
performance than the OCXO retrace can achieve itself.
 
It would be interesting to see if OCXO retrace is very repeatable, if yes  it 
could be compensated for of course.
 
Or leave the power on at all times after calibration.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Using a Vectron OCXO 5mhz oscilator with ntpd

[Bruce Griffiths]

Todd Eddy wrote:
> I'm still pretty new to the whole time keeping thing.  Currently I just
> run an ntp server for the ntp pool.  I've been looking at some ways to
> get direct reference but without being expensive.  Only thing I've seen
> within my budget so far is the garmin gps receivers that people like.
> Problem is the server is in a high security colo center and I doubt they
> would let me drill a hole in the roof to put a gps receiver.  I have
> started to see this 5mhz frequency quartz oscilators that are really
> inexpensive (see
> http://www.alltronics.com/cgi-bin/category.cgi?item=04P010 ).  My
> question, how would you get this to work with ntpd?  Seems like it work
> great for my situation where I can just put inside the rack behind the
> server, use some ntp servers to get the time to within 1 msec usually
> and then use this to get into the nanosecond accuracy.
>
> Only information I've looked at so far in using direct reference is
> looking at the gps receivers.  I did find information about using a
> "clock shaper" to convert the oscillator to a digital pps signal (see
> http://www.ko4bb.com/Timing/ClockShaper.html ) but that first one just
> looks really cryptic to me with knowing very little in the way of
> electronics.  Has anyone made one of these and made a more "dumbed down"
> writeup on how to set it up?
>
> I've tried scanning a few months back in the archives and only really
> came accross the above mentioned site.  Anyone have any other resources
> I can look into?  Thanks.
>   
Todd

The first clock shaper is about the simplest reasonably high performance
clock shaper that can be devised.
However your application doesnt actually require a particularly high
performance clock shaper, you could use an inverting gate with a
resistor connected between its input and output plus a capacitor to
couple the sinewave into its input as illustrated in the attached
schematic. Its difficult to get much simpler than this.

By itself, even dividing down a 5MHz crystal to produce a PPS output
(which could be used to sync an ntp) isnt a great deal of use without a
means of syncing the generated PPS output to UTC.
You could use the 5MHz signal together with a small synthesizer board to
replace the crystal on the PC motherboard, however all this does is
improve the stability of the PC  timebase. You still have the
synchronisation problem.

If you are really new to electronics then it would be better to buy an
already debugged  system, there are no shortcuts  to learning sufficient
about electronics, you have to read the books and build /debug real
circuits.

Bruce


ClockShaper2.pdf
Description: Adobe PDF document
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] WIRED Time Nuts

[Didier Juges]

Most likely, it depends even more on his attitude :-)

Didier 

> -Original Message-
> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Harris
> Sent: Tuesday, December 11, 2007 8:38 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] WIRED Time Nuts
> 
> Rex wrote:
> > Here's a time-related observation. As Andy Warhol specified, this 
> > could be your "15 minutes of fame".
> > 
> > Does anyone on the list have an accurate way to measure 
> fame minutes?
> 
> Probably depends on his altitude.
> 
> -Chuck Harris
> 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[Jeff Mock]

[EMAIL PROTECTED] wrote:
> Hi Bill,
>  
> a Rubidium would take about 15 to 20 Watts, and they don't  usually work at 
> 12V battery voltage typically.
>  
> At 20 Watts we would consume 1.67A at 12V, so a (large) 80Ah car batt would  
> only last two days in best conditions at room temperature.
>  
> If we add the OCXO power and low battery temperatures, then we are probably  
> down to 20 to 24 hours of operation or so.
>  
> BTW: interestingly Lead battery capacity is also related to discharge  
> current, not just temperature.
>  
> bye,
> Said
> 

I think the situation is somewhat better than that.  I'm looking at my 
LPRO-101.  It's about 18-watts while warming up, but once the physics 
package is up to temp and locked, the power consumption drops to about 
5-watts.  The larger rubidium modules are probably more power hungry, 
but the small onces aren't so bad once they are running.  You still 
might need a trunk full of batteries though...

jeff


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[SAIDJACK]

 
In a message dated 12/11/2007 15:39:50 Pacific Standard Time,  
[EMAIL PROTECTED] writes:

>OK,  so for the DAC piece, why not just use an NXP LPC ARM chip for  the
>microcontroller, and use a 32bit PCM output followed by a low pass  filter as
>the VXCO EFC?  The DAC just needs high resolution, not  accuracy, right?
>Or would the switching noise from the processor  modulate the control
>voltage?


Hi Scott,
 
one problem with using all 32 bits in the NXP LPC PWM output is that the  
counter can only run at typically 60MHz, the maximum CPU clock.
 
With a full 32 bits count time you would only get 2^32 / 60MHz pulses per  
second, or in other words (at 50% setting) a square wave with 71.6Hz.
 
That's pretty hard to filter out to get a very clean DC voltage so that  
there won't be a spur at 72Hz offset on the OCXO output. This would require  
large-capacitor filters.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[christopher hoover]

> What I use on the reflock II is a time lag counter from the 1pps to
> next clock, and this value drive a dac. Only a small integration time
> is done digitally and the large integration time if one requires that
> is done with a classical R and C without any active components right
> before the Vtune of the VCXO. 

The problem with reflock II as I recall for use with a 1PPS (w/sawtooth)
from a GPS receiver, is that the time constant is way too small.  You can't
integrate to a point anywhere near the Allan intercept of the receiver and
the XO.

-ch




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[SAIDJACK]

 
In a message dated 12/11/2007 17:00:17 Pacific Standard Time,  [EMAIL 
PROTECTED] 
writes:

>A  very high quality ocxo would probably satisfy the need.  Or as  someone
>suggested, a combination of ocxo and a Rb.  The Rb would  provide the longer 
term
>needed for the really high multiplication into  upper GHz region and the ocxo
>locked to Rb would [ possibly ] provide  the "quiet" drive  source.

>BillWB6BNQ



Hi Bill,
 
a Rubidium would take about 15 to 20 Watts, and they don't  usually work at 
12V battery voltage typically.
 
At 20 Watts we would consume 1.67A at 12V, so a (large) 80Ah car batt would  
only last two days in best conditions at room temperature.
 
If we add the OCXO power and low battery temperatures, then we are probably  
down to 20 to 24 hours of operation or so.
 
BTW: interestingly Lead battery capacity is also related to discharge  
current, not just temperature.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] WIRED Time Nuts

[Chuck Harris]

Rex wrote:
> Here's a time-related observation. As Andy Warhol specified, this could 
> be your "15 minutes of fame".
> 
> Does anyone on the list have an accurate way to measure fame minutes?

Probably depends on his altitude.

-Chuck Harris

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] WIRED Time Nuts

[Rex]

Here's a time-related observation. As Andy Warhol specified, this could 
be your "15 minutes of fame".

Does anyone on the list have an accurate way to measure fame minutes?

Good article, though.


Tom Van Baak wrote:
> Hi John & Rick,
>
> Looks like Quinn's WIRED magazine time-nuts article was just released...
>
> Article:
> http://www.wired.com/science/discoveries/news/2007/12/time_hackers
>
> Photos:
> http://www.wired.com/science/discoveries/multimedia/2007/12/gallery_time_hackers
>
> Index:
> http://www.wired.com/science/discoveries
>
> /tvb
> http://www.LeapSecond.com
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>   


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Using a Vectron OCXO 5mhz oscilator with ntpd

[Todd Eddy]

I'm still pretty new to the whole time keeping thing.  Currently I just
run an ntp server for the ntp pool.  I've been looking at some ways to
get direct reference but without being expensive.  Only thing I've seen
within my budget so far is the garmin gps receivers that people like.
Problem is the server is in a high security colo center and I doubt they
would let me drill a hole in the roof to put a gps receiver.  I have
started to see this 5mhz frequency quartz oscilators that are really
inexpensive (see
http://www.alltronics.com/cgi-bin/category.cgi?item=04P010 ).  My
question, how would you get this to work with ntpd?  Seems like it work
great for my situation where I can just put inside the rack behind the
server, use some ntp servers to get the time to within 1 msec usually
and then use this to get into the nanosecond accuracy.

Only information I've looked at so far in using direct reference is
looking at the gps receivers.  I did find information about using a
"clock shaper" to convert the oscillator to a digital pps signal (see
http://www.ko4bb.com/Timing/ClockShaper.html ) but that first one just
looks really cryptic to me with knowing very little in the way of
electronics.  Has anyone made one of these and made a more "dumbed down"
writeup on how to set it up?

I've tried scanning a few months back in the archives and only really
came accross the above mentioned site.  Anyone have any other resources
I can look into?  Thanks.


smime.p7s
Description: S/MIME Cryptographic Signature
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[michael taylor]

On Dec 11, 2007 6:38 PM, John Ackermann N8UR <[EMAIL PROTECTED]> wrote:
> > How long does a survey take (in good conditions) and what sort of time
> > constant would you want to use with a navigation box?
>
> It depends on the receiver, but usually it's a few hours to a full day.
>  Of course, if you use external software you can use whatever time
> period you want.

Newer navigation units offer 5Hz output, combined with SBAS (WAAS in
the US/Canada) for a more accurate measurement, you should be able to
do a "modest" survey in a few minutes. I believe the accuracy
continues to improve as survey time increases, up to a few hours.

-Michael

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Bruce Griffiths]

Luis

Luis Cupido wrote:
> Hi Bruce and Scott.
>
>  >> What about sampling both the VXCO and 1PPS at a 200MHZ rate?
>  >> That should determine the phase difference within no more than a 10ns
>  >> inaccuracy.
>  >>
>
> Simplicity is good but when using a CPLD or an FPGA no need to get
> simple if a better design still fits inside the chip ;-)
>
> Indeed those style of phase measuring schemes have far better 
> performance than the simple flip flop or similar.
>
>   
Not true, the effective measurement noise is only a few percent less
than that of a single bit phase detector (D flipflop) better with an
infinite resolution phase detector so why bother.
Single bit and 3 level ADCs are widely used in radio astronomy as except
when interference is a problem, multibit ADCs offer no significant
advantage.
> I say this because I had all the logic on a CPLD to play with
> so I tried a large number of phase locking schemes and
> could compare them.
>
>   
By all means try them, but why add the power consumption and complexity
of a CPLD if it offers little improvement in performance?
> First of all the lock capture range can become a bit
> independent of the integration time with a proportional phase lag
> counting method. Some counting methods will inherently search for lock
> when lock is lost. Some of those methods also have lock acquisition 
> times orders of magnitude smaller.
>
> On the other hand on CPLD (or FPGA) complexity doesn't cost more as
> this stuff is ultra extra small considering the size of
> a today's CPLD (eg. maxII w/ 1570 macrocells). No matter what you do
> a medium CPLD will be only used 10 to 20% not more.
>   
If you are going to use a CPLD you should also implement the processor
in the gate array as this reduces the PCB wiring complexity considerably.
> What I use on the reflock II is a time lag counter from the 1pps to
> next clock, and this value drive a dac. Only a small integration time
> is done digitally and the large integration time if one requires that
> is done with a classical R and C without any active components right
> before the Vtune of the VCXO. Therefore not a big DAC resolution is 
> required (I use 12-14bit) since the averaging is on the outside in an 
> analog filter in which simple 64 seconds integration time will grant
> you 6 bit more resolution.
>   
Trying to do all the filtering with an analog filter restricts the range
of loop response times to relatively small values degrading the
performance of the better OCXOs considerably.
Achieving time constants of 100 sec or more is somewhat
expensive/impractical using resistors and capacitors.
Some analog filtering is required but most of the long term filtering
should be done by the processor.
> It may look a strange combination of a modern devices and a old 
> fashioned filter but it had by far outperformed all the designs I could
> test w/ microporcessors + dac (in which some noise did get through),
> or lack stability.
>
>   
Layout and isolation of the DAC from processor created noise are critical.
> Luis Cupido
> ct1dmk.
> http://w3ref.cfn.ist.utl.pt/cupido/
>   

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Bruce Griffiths]

michael taylor wrote:
> On Dec 11, 2007 3:53 PM, Bruce Griffiths <[EMAIL PROTECTED]> wrote:
>   
>> If you want simplicity and higher performance you can do far better with
>> fewer parts,
>> An expensive high resolution DAC can be replaced with a software
>> sigma-delta DAC that has higher resolution.
>> The complex phase detector can be replaced with a D flipflop.
>> Add a microprocessor plus an opamp or 2 to filter and scale the EFC
>> voltage and thats about all thats required in addition to a good GPS
>> timing receiver.
>> For improved performance a hardware circuit to correct the PPS sawtooth
>> error will improve the medium term stability significantly when using a
>> high performance GPS timing receiver that provides an estimate of this
>> error.
>> 
>
> You have made similar comments about I believe the same approach in
> the past. I was wondering if you have ever sketched out a schematic,
> even if only rough. Perhaps with a few suggested components to try
> (i.e. DAC, Op-Amp) that would be a good starting point for anyone who
> wanted to prototype and evaluate the performance of this approach.
>
> It is beyond my elementary design abilities to convert your
> description into a well implemented design on my own, but I would be
> interested in try to at least see if I could construct an unit using
> these suggested techniques.
>
> -Michael
>
>   
Michael

Will provide a suitable circuit schematic for the DAC portion by around
1300 UTC.
The circuit will be suitable for either a PWM or a sigma-delta DAC.
The design will also include the ability to set (by selecting the values
of a couple of resistors) the EFC range to suit most OCXOs.

A sigma-delta DAC has the advantage that its easier to filter its output
than that of an equivalent resolution PWM DAC.

Combining a pair of lower resolution DACs with a few resistors will
produce a higher resolution output, however there will be problems with
monotonicity (when the coarse DAC output changes) unless the system is
periodically calibrated to  accommodate drifts due to temperature and
time. This can of course be done in software (no need for external
trimmers) however the calibration circuitry adds considerable complexity.

When testing the sigma delta DAC concept in software start with a simple
first order sigma delta modulator and then try a second order modulator
(dont go to higher order than a 2nd order modulator as they arent
necessary for this application and stabilisation of high order
modulators adds considerable complexity and can be difficult to achieve).

A suitable D flipflop phase detector design will follow shortly thereafter.

Do you also want a circuit for a sawtooth corrector using one of the
Maxim/Dallas programmable delay lines?

You will need to write the software for the sawtooth corrector and for
the D flip flop phase detector.
However I can provide descriptions of what the software needs to do,
along with suggestions for suitable algorithms.

Bruce


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[michael taylor]

On Dec 11, 2007 3:53 PM, Bruce Griffiths <[EMAIL PROTECTED]> wrote:
>
> If you want simplicity and higher performance you can do far better with
> fewer parts,
> An expensive high resolution DAC can be replaced with a software
> sigma-delta DAC that has higher resolution.
> The complex phase detector can be replaced with a D flipflop.
> Add a microprocessor plus an opamp or 2 to filter and scale the EFC
> voltage and thats about all thats required in addition to a good GPS
> timing receiver.
> For improved performance a hardware circuit to correct the PPS sawtooth
> error will improve the medium term stability significantly when using a
> high performance GPS timing receiver that provides an estimate of this
> error.

You have made similar comments about I believe the same approach in
the past. I was wondering if you have ever sketched out a schematic,
even if only rough. Perhaps with a few suggested components to try
(i.e. DAC, Op-Amp) that would be a good starting point for anyone who
wanted to prototype and evaluate the performance of this approach.

It is beyond my elementary design abilities to convert your
description into a well implemented design on my own, but I would be
interested in try to at least see if I could construct an unit using
these suggested techniques.

-Michael

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Luis Cupido]

Hi Bruce and Scott.

 >> What about sampling both the VXCO and 1PPS at a 200MHZ rate?
 >> That should determine the phase difference within no more than a 10ns
 >> inaccuracy.
 >>

Simplicity is good but when using a CPLD or an FPGA no need to get
simple if a better design still fits inside the chip ;-)

Indeed those style of phase measuring schemes have far better 
performance than the simple flip flop or similar.

I say this because I had all the logic on a CPLD to play with
so I tried a large number of phase locking schemes and
could compare them.

First of all the lock capture range can become a bit
independent of the integration time with a proportional phase lag
counting method. Some counting methods will inherently search for lock
when lock is lost. Some of those methods also have lock acquisition 
times orders of magnitude smaller.

On the other hand on CPLD (or FPGA) complexity doesn't cost more as
this stuff is ultra extra small considering the size of
a today's CPLD (eg. maxII w/ 1570 macrocells). No matter what you do
a medium CPLD will be only used 10 to 20% not more.

What I use on the reflock II is a time lag counter from the 1pps to
next clock, and this value drive a dac. Only a small integration time
is done digitally and the large integration time if one requires that
is done with a classical R and C without any active components right
before the Vtune of the VCXO. Therefore not a big DAC resolution is 
required (I use 12-14bit) since the averaging is on the outside in an 
analog filter in which simple 64 seconds integration time will grant
you 6 bit more resolution.

It may look a strange combination of a modern devices and a old 
fashioned filter but it had by far outperformed all the designs I could
test w/ microporcessors + dac (in which some noise did get through),
or lack stability.

Luis Cupido
ct1dmk.
http://w3ref.cfn.ist.utl.pt/cupido/













Bruce Griffiths wrote:
> Scott
> 
> Scott Burris wrote:
>> OK, so for the DAC piece, why not just use an NXP LPC ARM chip for the
>> microcontroller, and use a 32bit PCM output followed by a low pass filter as
>> the VXCO EFC?  The DAC just needs high resolution, not accuracy, right?
>>   
> True, but a Sigma delta DAC has far superior performance to a PWM DAC or
> a standard DAC especially when the long term stability is not critical
> and a faast response isnt required.
> NIST use sigma delta DACs in their precision AC waveform generator and
> to calibrate their Johnson noise thermometer systems.
>> Or would the switching noise from the processor modulate the control
>> voltage?
>>   
> Its best to have the processor drive an external current steering switch
> (74HC4053) to switch a stable current into the summing junction of an
> inverting opamp.
> If you want I can send you a suitable circuit schematic.
> With a suitable circuit one can just use a voltage reference and a
> resistor to set the current, a spare  analog switch can be used in
> series with the feedback resistor to provide temperature compensation 
> (important for good short and medium term stability). HP/Agilent in
> effect use a similar temperature compensated current steering technique
> in their 34401A 6.5 digit DVM.
> Ulrich has uses similar techniques albeit with the sigma delta DAC logic
> implemented in a gate array to achieve high resolution and good short
> term stability.
> In this application the DAC need not respond as fast so it can be
> implemented in software.
>> I would hope the filter would clean any such noise, but I'll be the first to
>> admit
>> that the farther we get into the analog domain, the more I'm out of my
>> comfort zone.
>>
>> I'm still trying to wrap my brain around the phase detection piece of this.
>> I've studied the Shera controller with it's 24Mhz oscillator and divided
>> down
>> sample of the VXCO and I'm can't get past thinking that this ends up
>> adding jitter.  With more modern parts can't the phase be measured more
>> directly?  What about sampling both the VXCO and 1PPS at a 200MHZ rate?
>> That should determine the phase difference within no more than a 10ns
>> inaccuracy.
>>
>>   
> Eliminate such unnecessary cost and complexity with a single D flipflop
> phase detector (D connected to 10MHz signal or a divided down
> subharmonic thereof, CLK connected to PPS) the circuit will
> automatically adapt to achieve a resolution determined by the PPS jitter
> (picoseconds if you have a good enough PPS source, a few nanosec with a
> sawtooth corrected PPS signal from an M12M timing receiver, a few tens
> of nanosec with an uncorrected PPS signal from an M12M timing receiver).
> Thus its resolution is far better than when using a 24MHz clock and its
> also cheaper and the hardware is less complex. Using a 200MHz clock just
> increases the cost and power consumption without significant benefit
> over the simpler D flipflop phase detector.
> However you will need to write suitable software to process the D
> flipflop output samples.

Re: [time-nuts] Fury Interface Board simulation results

[Bruce Griffiths]

George

The schematic for a more versatile EFC translator circuit is attached.
Any EFC range in the -10V to +10V range can be accomodated.
Even greater EFC ranges are possible by using a suitable opamp for U103
with appropriate power supplies.

The messy details of power supply bypassing etc are left as an exercise
together with calculating the necessary values for R107, R108, R109 for
OCXO EFC ranges other than [-5V, +5V].
Hint: select R107 to set the EFC span and either R108 or R109  to set
the EFC offset.
 
Bruce


FURY_EFC_TRANSLATOR.pdf
Description: Adobe PDF document
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz referenceoscilator

[WB6BNQ]

Hello to all,

I think everyone is missing the boat here, so to speak.  Eric does not
necessarily need a high degree of accuracy.

What he really needs is stability.  So if he was off frequency a bit, that could
be handled in the tunable IF unit, which is, most likely, some wide range modern
VHF/UHF tunable radio.

A very high quality ocxo would probably satisfy the need.  Or as someone
suggested, a combination of ocxo and a Rb.  The Rb would provide the longer term
needed for the really high multiplication into upper GHz region and the ocxo
locked to Rb would [ possibly ] provide the "quiet" drive source.

BillWB6BNQ

Eric Fort wrote:

> I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
> reference (probably quartz based) with enough stability over a period
> of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
> within 100hz  while mountaintop contesting.  Suggestions are
> appreciated.  something that is small and ran off 12 volts dc (car
> battery) would be a definite plus.
>
> Thanks,
>
> Eric
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Stan]

Hello Eric,

I picked up a few ISOTEMP VCXOs from Pyro Joe on ebay. 12VDC operation

Currently using one as a 10 MHz reference for my AD6IW PLL osc for the 
LO on my DB6NT 10 G2.
For the control voltage, I use a multi turn pot and cal at home, before 
the contest weekend.
I am tickled with the frequency stability. I use mostly USB and CW.

I packaged it up in a diecast box to keep the wind off.
Plan is to expand the concept to 24, 47, and 78 GHz.

If I need more frequency stability for the processing gain in a 
ARGO/QRSS CW mode,
I can migrate to a Rb in the portable station.

Stan, W1LE   FN41sr   Cape Cod



Eric Fort wrote:
> I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
> reference (probably quartz based) with enough stability over a period
> of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
> within 100hz  while mountaintop contesting.  Suggestions are
> appreciated.  something that is small and ran off 12 volts dc (car
> battery) would be a definite plus.
>
> Thanks,
>
> Eric
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>   


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] time-nuts Digest, Vol 41, Issue 36

[Scott Dennis]

To TVB:  Really enjoyed the article!  Especially the part about the GREAT
experiment.  But it was nice just to see your picture after all these
years.  Think I'll camp out here and see what kinds of esoterica you guys
come up with here.
  --Scott Dennis AL7EM

P.S.  Yes, I did eventually graduate.


On Dec 11, 2007 3:59 PM, <[EMAIL PROTECTED]> wrote:

> Send time-nuts mailing list submissions to
>time-nuts@febo.com
>
> To subscribe or unsubscribe via the World Wide Web, visit
>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> or, via email, send a message with subject or body 'help' to
>[EMAIL PROTECTED]
>
> You can reach the person managing the list at
>[EMAIL PROTECTED]
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of time-nuts digest..."
>
>
> Today's Topics:
>
>   1. Re: is there a "best bet" advanced hobbyist buildable
>  GPSDOdesign? (Scott Burris)
>   2. Re: need recomendation for a portable 10mhz reference
>  oscilator (John Ackermann N8UR)
>   3. Re: Fury Interface Board simulation results (Bruce Griffiths)
>   4. Re: WIRED Time Nuts (Keith E. Brandt, M.D.)
>
>
> --
>
> Message: 1
> Date: Tue, 11 Dec 2007 15:38:31 -0800
> From: "Scott Burris" <[EMAIL PROTECTED]>
> Subject: Re: [time-nuts] is there a "best bet" advanced hobbyist
>buildable   GPSDOdesign?
> To: "Discussion of precise time and frequency measurement"
>
> Message-ID:
><[EMAIL PROTECTED]>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On Dec 11, 2007 12:53 PM, Bruce Griffiths <[EMAIL PROTECTED]>
> wrote:
>
> > Tom Van Baak wrote:
> > >> Hi,
> > >>
> > >> Like many, I've acquired a fair amount of surplus test equipment off
> of
> > Ebay
> > >> which could use the services of good master frequency standard.  So
> I'm
> > >> looking to discipline an HP 10811 VXCO to provide this.
> > >>
> > >> Any general consensus about the best design for a hobbyist to build?
> > >> I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T
> design,
> > >> the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
> > >> I've seen in the archives of this list that the VE2ZAZ design makes a
> > >> number of simplification/performance tradeoffs.
> > >>
> > >> Is there a design I haven't listed which is "better" than the others?
> > >> I'm quite familiar with microcontrollers, FPGAs, spinning my own
> > >> PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
> > >> a variation on someone's tried and true design.
> > >>
> > >> I'm aware of products like the Fury, but I'd like something I could
> > tinker
> > >> with, and the cost is hard to justify for a hobbyist.
> > >>
> > >> Scott
> > >>
> > >
> > > Scott,
> > >
> > > Hard to say which is better at this point; there are a number
> > > of variables, not the least of which is the intrinsic short-term
> > > stability of the OCXO you use.
> > >
> > > Do have a close look at James Miller's GPSDO:
> > >
> > > http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm
> > >
> > > I recently tested one and it makes it to 1e-13 at one day, which
> > > is really nice for a simple, cheap, homebrew GPSDO.
> > >
> > > /tvb
> > >
> > >
> > > ___
> > > time-nuts mailing list -- time-nuts@febo.com
> > > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> > >
> > Tom
> >
> > What about the short term performance?
> > Its relatively easy to achieve a stability of 1E-13 for an averaging
> > time of 1 day, achieving good short or medium term stability is more
> > difficult.
> >
> > If you want simplicity and higher performance you can do far better with
> > fewer parts,
> > An expensive high resolution DAC can be replaced with a software
> > sigma-delta DAC that has higher resolution.
> > The complex phase detector can be replaced with a D flipflop.
> > Add a microprocessor plus an opamp or 2 to filter and scale the EFC
> > voltage and thats about all thats required in addition to a good GPS
> > timing receiver.
> > For improved performance a hardware circuit to correct the PPS sawtooth
> > error will improve the medium term stability significantly when using a
> > high performance GPS timing receiver that provides an estimate of this
> > error.
> >
> > Both the Brooks Shera and the James Miller designs have inadequate phase
> > error measurement resolution to achieve good short and medium term
> > stability.
> > However, this is only noticeable when using high performance GPS timing
> > receivers (M12+T, M12MT etc) and a high quality OCXO (10811A etc).
> >
> > Bruce
> >
> > ___
> >
>
> OK, so for the DAC piece, why not just use an NXP LPC ARM chip for the
> microcontroller, and use a 32bit PCM output followed by a low pass filter
> as
>

Re: [time-nuts] WIRED Time Nuts

[Bruce Griffiths]

Keith E. Brandt, M.D. wrote:
> So, what's the 'hockey puck' clock mentioned in the article?
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>   
The HP/Agilent E1938A.
http://www.leapsecond.com/museum/e1938a/

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Bruce Griffiths]

Scott

Scott Burris wrote:
>
> OK, so for the DAC piece, why not just use an NXP LPC ARM chip for the
> microcontroller, and use a 32bit PCM output followed by a low pass filter as
> the VXCO EFC?  The DAC just needs high resolution, not accuracy, right?
>   
True, but a Sigma delta DAC has far superior performance to a PWM DAC or
a standard DAC especially when the long term stability is not critical
and a faast response isnt required.
NIST use sigma delta DACs in their precision AC waveform generator and
to calibrate their Johnson noise thermometer systems.
> Or would the switching noise from the processor modulate the control
> voltage?
>   
Its best to have the processor drive an external current steering switch
(74HC4053) to switch a stable current into the summing junction of an
inverting opamp.
If you want I can send you a suitable circuit schematic.
With a suitable circuit one can just use a voltage reference and a
resistor to set the current, a spare  analog switch can be used in
series with the feedback resistor to provide temperature compensation 
(important for good short and medium term stability). HP/Agilent in
effect use a similar temperature compensated current steering technique
in their 34401A 6.5 digit DVM.
Ulrich has uses similar techniques albeit with the sigma delta DAC logic
implemented in a gate array to achieve high resolution and good short
term stability.
In this application the DAC need not respond as fast so it can be
implemented in software.
> I would hope the filter would clean any such noise, but I'll be the first to
> admit
> that the farther we get into the analog domain, the more I'm out of my
> comfort zone.
>
> I'm still trying to wrap my brain around the phase detection piece of this.
> I've studied the Shera controller with it's 24Mhz oscillator and divided
> down
> sample of the VXCO and I'm can't get past thinking that this ends up
> adding jitter.  With more modern parts can't the phase be measured more
> directly?  What about sampling both the VXCO and 1PPS at a 200MHZ rate?
> That should determine the phase difference within no more than a 10ns
> inaccuracy.
>
>   
Eliminate such unnecessary cost and complexity with a single D flipflop
phase detector (D connected to 10MHz signal or a divided down
subharmonic thereof, CLK connected to PPS) the circuit will
automatically adapt to achieve a resolution determined by the PPS jitter
(picoseconds if you have a good enough PPS source, a few nanosec with a
sawtooth corrected PPS signal from an M12M timing receiver, a few tens
of nanosec with an uncorrected PPS signal from an M12M timing receiver).
Thus its resolution is far better than when using a 24MHz clock and its
also cheaper and the hardware is less complex. Using a 200MHz clock just
increases the cost and power consumption without significant benefit
over the simpler D flipflop phase detector.
However you will need to write suitable software to process the D
flipflop output samples.
> Or use a pulse stretching technique to amplify the short time intervals into
> something
> more easily measured, although that's beyond what I'm familiar with.
>
>   
Again easily done but more complex than required.
> I've read the PTTI presentation about using a DS1020 delay line to
> de-sawtooth the
> 1PPS signal -- that's a pretty interesting idea.  At least the chip is
> available in Qty 1,
> at $30!
>
>   
That is a very good idea for getting the maximum performance with a D
flipflop phase detector and an M12M or similar GPS timing receiver.
You can do far better when using GPS carrier phase disciplining
techniques and the GPS receiver has all the necessary high resolution
phase measurement circuitry built in.
However considerable software development is required together with a
GPS receiver that makes the GPS carrier phase measurement data available.
> It just seems that the designs I've seen could use a refresh with some more
> modern
> circuitry.  At the very least the Shera controller could have much of its
> logic put into
> a single CPLD these days.
>
> Scott
> ___
>   
The Shera controller is a dead end, it doesnt have sufficient resolution
and whilst increasing its resolution is possible there are simpler,
better and cheaper ways to achieve this.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] WIRED Time Nuts

[Keith E. Brandt, M.D.]

So, what's the 'hockey puck' clock mentioned in the article?


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[Bruce Griffiths]

George

The circuit schematic for a BJT version of the JFET frequency is attached.
The biasing is a little more complex as it is necessary set each
frequency doubler BJT collector current at about 1mA or so to maximise
conversion gain.
The input impedance  is also around 50 ohms.
Have also minimised the number of different component values used.
Other transistors may be substituted but some care is required as the 
reverse voltage across the base emitter junction is about 2V for a
+13dBm input.
Some filtering of the output waveform is required.
The intended output load is 50 ohms.

The 200 ohm emitter series resistors together with the transformed
source impedance ensure that there is sufficient degeneration to keep
the phase noise low.

Obtaining suitable transistors for this circuit should be much easier
than obtaining suitable JFETS for the JFET doubler.

Whilst a diode doubler (at higher frequencies this may be the only
sensible option) could be used it would need both an input amplifier and
an output amplifier.

Bruce


CommonBaseBJTFrquencyDoubler.pdf
Description: Adobe PDF document
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Scott Burris]

On Dec 11, 2007 12:53 PM, Bruce Griffiths <[EMAIL PROTECTED]>
wrote:

> Tom Van Baak wrote:
> >> Hi,
> >>
> >> Like many, I've acquired a fair amount of surplus test equipment off of
> Ebay
> >> which could use the services of good master frequency standard.  So I'm
> >> looking to discipline an HP 10811 VXCO to provide this.
> >>
> >> Any general consensus about the best design for a hobbyist to build?
> >> I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T design,
> >> the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
> >> I've seen in the archives of this list that the VE2ZAZ design makes a
> >> number of simplification/performance tradeoffs.
> >>
> >> Is there a design I haven't listed which is "better" than the others?
> >> I'm quite familiar with microcontrollers, FPGAs, spinning my own
> >> PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
> >> a variation on someone's tried and true design.
> >>
> >> I'm aware of products like the Fury, but I'd like something I could
> tinker
> >> with, and the cost is hard to justify for a hobbyist.
> >>
> >> Scott
> >>
> >
> > Scott,
> >
> > Hard to say which is better at this point; there are a number
> > of variables, not the least of which is the intrinsic short-term
> > stability of the OCXO you use.
> >
> > Do have a close look at James Miller's GPSDO:
> >
> > http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm
> >
> > I recently tested one and it makes it to 1e-13 at one day, which
> > is really nice for a simple, cheap, homebrew GPSDO.
> >
> > /tvb
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> >
> Tom
>
> What about the short term performance?
> Its relatively easy to achieve a stability of 1E-13 for an averaging
> time of 1 day, achieving good short or medium term stability is more
> difficult.
>
> If you want simplicity and higher performance you can do far better with
> fewer parts,
> An expensive high resolution DAC can be replaced with a software
> sigma-delta DAC that has higher resolution.
> The complex phase detector can be replaced with a D flipflop.
> Add a microprocessor plus an opamp or 2 to filter and scale the EFC
> voltage and thats about all thats required in addition to a good GPS
> timing receiver.
> For improved performance a hardware circuit to correct the PPS sawtooth
> error will improve the medium term stability significantly when using a
> high performance GPS timing receiver that provides an estimate of this
> error.
>
> Both the Brooks Shera and the James Miller designs have inadequate phase
> error measurement resolution to achieve good short and medium term
> stability.
> However, this is only noticeable when using high performance GPS timing
> receivers (M12+T, M12MT etc) and a high quality OCXO (10811A etc).
>
> Bruce
>
> ___
>

OK, so for the DAC piece, why not just use an NXP LPC ARM chip for the
microcontroller, and use a 32bit PCM output followed by a low pass filter as
the VXCO EFC?  The DAC just needs high resolution, not accuracy, right?
Or would the switching noise from the processor modulate the control
voltage?
I would hope the filter would clean any such noise, but I'll be the first to
admit
that the farther we get into the analog domain, the more I'm out of my
comfort zone.

I'm still trying to wrap my brain around the phase detection piece of this.
I've studied the Shera controller with it's 24Mhz oscillator and divided
down
sample of the VXCO and I'm can't get past thinking that this ends up
adding jitter.  With more modern parts can't the phase be measured more
directly?  What about sampling both the VXCO and 1PPS at a 200MHZ rate?
That should determine the phase difference within no more than a 10ns
inaccuracy.

Or use a pulse stretching technique to amplify the short time intervals into
something
more easily measured, although that's beyond what I'm familiar with.

I've read the PTTI presentation about using a DS1020 delay line to
de-sawtooth the
1PPS signal -- that's a pretty interesting idea.  At least the chip is
available in Qty 1,
at $30!

It just seems that the designs I've seen could use a refresh with some more
modern
circuitry.  At the very least the Shera controller could have much of its
logic put into
a single CPLD these days.

Scott
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[John Ackermann N8UR]

Hal Murray said the following on 12/11/2007 05:57 PM:
>> As great as GPSDO are, the problem with using them in a portable
>> environment is the time it takes to do a survey and then get to final
>> lock; mountain-toppers may not be in one place long enough. 
> 
> What if you use a navigation GPS unit rather than a timing unit?

To get decent (for some definition of "decent") timing, you need to
operate the receiver in "0-D" mode, telling it where it is and letting
it solve just for time.  I haven't done the experiments myself but I
believe that the time accuracy is pretty dramatically degraded when
operating in 2-D or 3-D mode.

> How long does a survey take (in good conditions) and what sort of time 
> constant would you want to use with a navigation box?

It depends on the receiver, but usually it's a few hours to a full day.
 Of course, if you use external software you can use whatever time
period you want.

John

> Does anybody have graphs of the PPS wander from a navigation unit?
> 
> 
> I like the lock-to-rubidium suggestion.
> 
> 


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Alan Melia]

Hi John, Andy Talbot G4JNT developed the a Jupiter based GPSDO for just this
purpose, several are used by hill-toppers in the UK.
http://www.scrbg.org/g4jnt/freqlock.htm
The idea was that it would settle and be accurate in the time it took to
seet up the microwave part of the station.

I hope that helps/
Alan G3NYK

- Original Message -
From: "John Ackermann N8UR" <[EMAIL PROTECTED]>
To: "Discussion of precise time and frequency measurement"

Sent: Tuesday, December 11, 2007 8:56 PM
Subject: Re: [time-nuts] need recomendation for a portable 10mhz reference
oscilator


> Hal Murray wrote:
> > I'm picturing an open hill top at night with clear skies so there would
be
> > lots of radiation cooling.  Of course, with an open hill top, GPS
recption
> > would be easy.
>
> As great as GPSDO are, the problem with using them in a portable
> environment is the time it takes to do a survey and then get to final
> lock; mountain-toppers may not be in one place long enough.
>
> One thought I've had is to use a cheap Rubidium for long term stability,
> and phase lock a good OCXO to it for short term stability and phase
> noise (ie, use a loop time constant of perhaps 100 seconds).  That would
> make a portable package that would meet both the short and long term
> stability requirements.
>
> John
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Hal Murray]

> As great as GPSDO are, the problem with using them in a portable
> environment is the time it takes to do a survey and then get to final
> lock; mountain-toppers may not be in one place long enough. 

What if you use a navigation GPS unit rather than a timing unit?

How long does a survey take (in good conditions) and what sort of time 
constant would you want to use with a navigation box?

Does anybody have graphs of the PPS wander from a navigation unit?


I like the lock-to-rubidium suggestion.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[Bruce Griffiths]

xaos wrote:
> Bruce Griffiths wrote:
>   
>> George
>>
>> In the JFET frequency doubler:
>> 1) Surely the 50 ohms should be is series with the the voltage source V3
>> for the simulation?
>>   
>> 
> Correct. I did a cut and paste "without rotate" there.
>   
>> 2) Usually a 1:4 impedance ratio step up transformer on the input is
>> about right with a similar transformer used to step down the output
>> (perhaps an even higher impedance ratio transformer (8:1, 9:1?? may be
>> better). The maximum turns ratio depends somewhat on the maximum
>> allowable drain voltage swing which in turn is limited by the drain
>> supply voltage.
>>   
>> 
> I will re-run with the this in mind and will repost.
>   
The idea is that the FETs are not operated in the square law region but
are actually switched off alternately so that the combined drain current
waveform is a rectified sinewave with a small dc offset.
With a well balanced circuit the odd harmonic amplitudes (including the
fundamental) at the output will be small with the 20MHz 4th harmonic of
the fundamental being the largest component.
Achieving low distortion isnt the aim, but achieving low phase noise is.
Any residual harmonics and subharmonics can be removed with tuned
circuit traps (dont use a high Q bandpass filter as it will inevitably
have a high phase shift tempco and may add flicker phase noise depending
on the components used). A relatively broadband low pass filter
contributes little phase shift (and associated flicker phase noise as
well as little phase shift tempco) at 10MHz as do a series of relatively
high Q LC traps. High performance is rarely achieved by the
simplest/obvious solution.
If you have difficulty finding suitable JFETs a high impedance bipolar
junction transistor (BJT) implementation is also possible however
biasing is a little trickier and requires a couple of extra BJTs to
ensure reasonable thermal stability of the bias currents.
>> In the voltage offset circuit:
>>
>> 1) The junction of R9 and R12 should be connected to the offset source
>> (+5V??).
>>   
>> 
> This is what I didn't get about the original circuit.  I was scratching 
> my head as to the purpose of a variable R9 when
> the only value that made sense was when it was set to the "0" position.
>
>   
>> I dont understand what the 7812 does in this circuit.
>>   
>> 
> It was there in the original circuit so I modeled accordingly. Actually 
> I ran some simulations with PS voltage variation
> to see the effect as well. In that case I removed the 7812.
>   
>> Isolation amplifier looks OK.
>>
>> Bruce
>>   
>> 
> This is a very nice design and the AC analysis shows a bandpass around 
> 10 MHz with 20 MHz BW.
>
> The only issue I see there is that it needs 50 parts of 6 different values.
>
> This might be difficult to implement on a small board and would be prone 
> to error for people trying to
> assemble their own board.
>
> The way I see the final product is a bare board and possibly a kit. It 
> has to be easy to assemble and minimize
> errors.
>
> Actually, I was looking at the isolation amplifier provided in the C.M. 
> Felton Paper:
>
> http://www.darksmile.net/ee/Superimposing_Low-Phase-Noise_Low-Drift_Instrumentation_Techniques_On_RF_Design.pdf
>
> It is relatively simple and would use similar devices as the Frequency 
> doubler.
>   
The trouble with this design is that it has a low input impedance and
thus is unsuitable for OCXOs that require a high impedance load (eg 10544A).
Its gain isnt adjustable and its difficult to obtain suitable dual JFETS
(you would have to use a couple of J310's to achieve similar performance
since U431 isnt readily obtainable, the LS840 is definitely unsuitable
as its minimum Idss isnt high enough ), it also has relatively low
reverse isolation. Simplicity isnt the key to high performance.
> I will upload more info as I compile it.
>
> George
>   


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Bruce Griffiths]

John Ackermann N8UR wrote:
> Hal Murray wrote:
>   
>> I'm picturing an open hill top at night with clear skies so there would be 
>> lots of radiation cooling.  Of course, with an open hill top, GPS recption 
>> would be easy.
>> 
>
> As great as GPSDO are, the problem with using them in a portable 
> environment is the time it takes to do a survey and then get to final 
> lock; mountain-toppers may not be in one place long enough.
>
> One thought I've had is to use a cheap Rubidium for long term stability, 
> and phase lock a good OCXO to it for short term stability and phase 
> noise (ie, use a loop time constant of perhaps 100 seconds).  That would 
> make a portable package that would meet both the short and long term 
> stability requirements.
>
> John
>   
John

Why not lock it to a GPS timing receiver output when its at home, and
allow the controller to learn the aging and tempco characteristics etc
of the oscillator being disciplined and use this information to correct
for temperature variations etc at the remote site?

The model used can be as complex as required to achieve the desired
performance and a PC can be used to derive optimum correction
coefficients, the micro only has to perform the simpler task of applying
these corrections.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Bruce Griffiths]

Hal Murray wrote:
>> A good (and well-aged) double-oven OCXO with aging compensation should
>> be able to provide that type of performance. The problem is: how
>> much physical movement will the unit experience? What are the
>> temperature extremes that are expected, and how fast does the
>> ambient move between the temp extremes? Can it be GPS locked during
>> that time? 
>> 
>
> Assuming you don't GPS lock it...
>
> How well will two units from the same manufacturer/batch track?
>
> I'm assuming they will see roughly the same temperature profile and that you 
> start with them running at the same frequency.
>
>
> Has anybody made a triple oven setup?  I'm thinking of a big box with a few 
> holes and a temperature controlled fan.  The idea is to let the oven (and 
> electronics) keep itself warm when the ambient temperature gets very cold.
>
> I'm picturing an open hill top at night with clear skies so there would be 
> lots of radiation cooling.  Of course, with an open hill top, GPS recption 
> would be easy.
>
>
>
>   
Hal,

A triple oven is a particularly bad idea, its just too difficult to
achieve a wide operating temperature range without losing temperature
control or cooking everything in the innermost oven unless one uses a
watercooled peltier device to control the outer oven temperature.

A well designed single oven with feedforward (or the outer oven of a
dual oven system if you cant redesign/rebuild the inner oven) can easily
achieve a thermal gain of more than 1E5 see:

http://tf.nist.gov/timefreq/general/pdf/595.pdf



A bootstrapped oven design like that used by Wenzel (not as new as he'd
have you believe - its been in use in one form or another for the better
part of a century) will also help in improving performance. The optimum
solution is of course to combine the 2 techniques.

http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf

With a thermal gain of 1E5 for the outer oven temperature fluctuations
at the outer shell of the inner oven will only be a 1 millikelvin or so
(assuming the ambient temperature range is less than 100K).

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[John Ackermann N8UR]

Hal Murray wrote:
> I'm picturing an open hill top at night with clear skies so there would be 
> lots of radiation cooling.  Of course, with an open hill top, GPS recption 
> would be easy.

As great as GPSDO are, the problem with using them in a portable 
environment is the time it takes to do a survey and then get to final 
lock; mountain-toppers may not be in one place long enough.

One thought I've had is to use a cheap Rubidium for long term stability, 
and phase lock a good OCXO to it for short term stability and phase 
noise (ie, use a loop time constant of perhaps 100 seconds).  That would 
make a portable package that would meet both the short and long term 
stability requirements.

John

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Bruce Griffiths]

Tom Van Baak wrote:
>> Hi,
>>
>> Like many, I've acquired a fair amount of surplus test equipment off of Ebay
>> which could use the services of good master frequency standard.  So I'm
>> looking to discipline an HP 10811 VXCO to provide this.
>>
>> Any general consensus about the best design for a hobbyist to build?
>> I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T design,
>> the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
>> I've seen in the archives of this list that the VE2ZAZ design makes a
>> number of simplification/performance tradeoffs.
>>
>> Is there a design I haven't listed which is "better" than the others?
>> I'm quite familiar with microcontrollers, FPGAs, spinning my own
>> PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
>> a variation on someone's tried and true design.
>>
>> I'm aware of products like the Fury, but I'd like something I could tinker
>> with, and the cost is hard to justify for a hobbyist.
>>
>> Scott
>> 
>
> Scott,
>
> Hard to say which is better at this point; there are a number
> of variables, not the least of which is the intrinsic short-term
> stability of the OCXO you use.
>
> Do have a close look at James Miller's GPSDO:
>
> http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm
>
> I recently tested one and it makes it to 1e-13 at one day, which
> is really nice for a simple, cheap, homebrew GPSDO.
>
> /tvb
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>   
Tom

What about the short term performance?
Its relatively easy to achieve a stability of 1E-13 for an averaging
time of 1 day, achieving good short or medium term stability is more
difficult.

If you want simplicity and higher performance you can do far better with
fewer parts,
An expensive high resolution DAC can be replaced with a software
sigma-delta DAC that has higher resolution.
The complex phase detector can be replaced with a D flipflop.
Add a microprocessor plus an opamp or 2 to filter and scale the EFC
voltage and thats about all thats required in addition to a good GPS
timing receiver.
For improved performance a hardware circuit to correct the PPS sawtooth
error will improve the medium term stability significantly when using a
high performance GPS timing receiver that provides an estimate of this
error.

Both the Brooks Shera and the James Miller designs have inadequate phase
error measurement resolution to achieve good short and medium term
stability.
However, this is only noticeable when using high performance GPS timing
receivers (M12+T, M12MT etc) and a high quality OCXO (10811A etc).

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Magnus Danielson]

From: "Eric Fort" <[EMAIL PROTECTED]>
Subject: [time-nuts] need recomendation for a portable 10mhz reference oscilator
Date: Tue, 11 Dec 2007 11:38:40 -0800
Message-ID: <[EMAIL PROTECTED]>

Eric,

> I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
> reference (probably quartz based) with enough stability over a period
> of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
> within 100hz  while mountaintop contesting.  Suggestions are
> appreciated.  something that is small and ran off 12 volts dc (car
> battery) would be a definite plus. 

Have a look at the Oscilloquartz 8711/8712 (G option, you would need
< 3E-10/day, so 2E-10/day fits your needs, but maybe you can live with the
164,5 Hz the standard 5E-10/day would give you) for instance.
Hook up a DAC and a small PIC or AVR to keep the DAC easilly controlable when
calibrating the frequency in the home lab.

There are many similar oscillators which will do the same trick. A 10811 would
also do the same thing, but it requires a higher voltage but a switcher would
double up the 12V.

Cheers,
Magnus

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[Hal Murray]

> A good (and well-aged) double-oven OCXO with aging compensation should
> be able to provide that type of performance. The problem is: how
> much physical movement will the unit experience? What are the
> temperature extremes that are expected, and how fast does the
> ambient move between the temp extremes? Can it be GPS locked during
> that time? 

Assuming you don't GPS lock it...

How well will two units from the same manufacturer/batch track?

I'm assuming they will see roughly the same temperature profile and that you 
start with them running at the same frequency.


Has anybody made a triple oven setup?  I'm thinking of a big box with a few 
holes and a temperature controlled fan.  The idea is to let the oven (and 
electronics) keep itself warm when the ambient temperature gets very cold.

I'm picturing an open hill top at night with clear skies so there would be 
lots of radiation cooling.  Of course, with an open hill top, GPS recption 
would be easy.



-- 
These are my opinions, not necessarily my employer's.  I hate spam.




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDO design?

[Luis Cupido]

Scott, you have also:
http://w3ref.cfn.ist.utl.pt/cupido/reflock.html

lab grade consider using reflock II
for kits I think TAPR still has those...


Luis Cupido
ct1dmk.


Scott Burris wrote:
> Hi,
> 
> Like many, I've acquired a fair amount of surplus test equipment off of Ebay
> which could use the services of good master frequency standard.  So I'm
> looking to discipline an HP 10811 VXCO to provide this.
> 
> Any general consensus about the best design for a hobbyist to build?
> I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T design,
> the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
> I've seen in the archives of this list that the VE2ZAZ design makes a
> number of simplification/performance tradeoffs.
> 
> Is there a design I haven't listed which is "better" than the others?
> I'm quite familiar with microcontrollers, FPGAs, spinning my own
> PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
> a variation on someone's tried and true design.
> 
> I'm aware of products like the Fury, but I'd like something I could tinker
> with, and the cost is hard to justify for a hobbyist.
> 
> Scott
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] need recomendation for a portable 10mhz reference oscilator

[SAIDJACK]

 
In a message dated 12/11/2007 11:41:02 Pacific Standard Time,  
[EMAIL PROTECTED] writes:

>I'm  looking for a fairly basic, relatively simple 10 Mhz PORTABLE
>reference  (probably quartz based) with enough stability over a period
>of a week  of outdoor temp extremes to keep a 47Ghz transmitter locked
>within  100hz  while mountaintop contesting.  Suggestions  are
>appreciated.  something that is small and ran off 12 volts dc  (car
>battery) would be a definite  plus.

>Thanks,

>Eric


Hi Eric,
 
if my math is correct, you will need about 26.3 microseconds holdover  
performance per day to achieve that requirement.
 
A good (and well-aged) double-oven OCXO with aging compensation should be  
able to provide that type of performance. The problem is: how much physical  
movement will the unit experience? What are the temperature extremes that are  
expected, and how fast does the ambient move between the temp extremes? Can it  
be GPS locked during that time?
 
Our Fury double-oven OCXO GPSDO may be a bit expensive for this  application, 
but if you can keep it within the 0C to 70C temperature range of  the OCXO 
(by proper thermal shielding) then it would fulfill all of  your needs.
 
The electronics themselves are rated to operate down to -20C, so only the  
OCXO needs attention to be well shielded thermally so as to keep it  
self-heating at a comfortable temperature.
 
Aging in holdover is typically better than 7 microseconds per day at room  
temp, and it runs from a Lead Acid car battery, all the way down to 11.0V.
 
If you can use a GPS antenna, the performance would be better than your  
requirement of course.
 
Expect it to draw about 5W, depending on temperature, so a typical 80Ah  
battery (derated for low temperature to say 40Ah) would last about 40Ah/0.45A = 
 
3.7 days to 7.4 days depending on the performance of the Pb battery. But you  
should really use a marine deep-discharge battery, your car batt may die when  
deep-discharged, especially at low temp.
 
At low temperatures Pb batt's have much lower voltage than at room temp, so  
you will need to be able to go down to <12.0V.
 
A small solar array (2W to 5W) and a bit of sun may extend that  operating 
time significantly.
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] need recomendation for a portable 10mhz reference oscilator

[Eric Fort]

I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
reference (probably quartz based) with enough stability over a period
of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
within 100hz  while mountaintop contesting.  Suggestions are
appreciated.  something that is small and ran off 12 volts dc (car
battery) would be a definite plus.

Thanks,

Eric

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

[Tom Van Baak]

> Hi,
> 
> Like many, I've acquired a fair amount of surplus test equipment off of Ebay
> which could use the services of good master frequency standard.  So I'm
> looking to discipline an HP 10811 VXCO to provide this.
> 
> Any general consensus about the best design for a hobbyist to build?
> I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T design,
> the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
> I've seen in the archives of this list that the VE2ZAZ design makes a
> number of simplification/performance tradeoffs.
> 
> Is there a design I haven't listed which is "better" than the others?
> I'm quite familiar with microcontrollers, FPGAs, spinning my own
> PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
> a variation on someone's tried and true design.
> 
> I'm aware of products like the Fury, but I'd like something I could tinker
> with, and the cost is hard to justify for a hobbyist.
> 
> Scott

Scott,

Hard to say which is better at this point; there are a number
of variables, not the least of which is the intrinsic short-term
stability of the OCXO you use.

Do have a close look at James Miller's GPSDO:

http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm

I recently tested one and it makes it to 1e-13 at one day, which
is really nice for a simple, cheap, homebrew GPSDO.

/tvb


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] We are in Slashdot

[Keith Payea]

The article is also referenced at Make Magazine:

http://blog.makezine.com/archive/2007/12/time_hackers.html

I highly recommend this magazine for all the tinkerers out there.

Keith 

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of [EMAIL PROTECTED]
Sent: Tuesday, December 11, 2007 9:43 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] We are in Slashdot

This was the story at Slashdot today.

http://hardware.slashdot.org/article.pl?sid=07/12/11/0517234

I bet some of our guys (febo, leapsecond) are seeing an increased  
volume as well.

-George


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] We are in Slashdot

[Robert Vassar]

Probably picked up a few new list members as well...


O:-)


de KC6OOM/5
[EMAIL PROTECTED]
[EMAIL PROTECTED]


On Dec 11, 2007, at 11:42 AM, [EMAIL PROTECTED] wrote:

> This was the story at Slashdot today.
>
> http://hardware.slashdot.org/article.pl?sid=07/12/11/0517234
>
> I bet some of our guys (febo, leapsecond) are seeing an increased
> volume as well.
>
> -George
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ 
> time-nuts
> and follow the instructions there.


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] We are in Slashdot

[xaos]

This was the story at Slashdot today.

http://hardware.slashdot.org/article.pl?sid=07/12/11/0517234

I bet some of our guys (febo, leapsecond) are seeing an increased  
volume as well.

-George


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] is there a "best bet" advanced hobbyist buildable GPSDO design?

[Scott Burris]

Hi,

Like many, I've acquired a fair amount of surplus test equipment off of Ebay
which could use the services of good master frequency standard.  So I'm
looking to discipline an HP 10811 VXCO to provide this.

Any general consensus about the best design for a hobbyist to build?
I'm familiar with the Brooks Shera design, the G4JNT Jupiter-T design,
the TAC-2 circuit, and the VE2ZAZ design.  I take it from discussions
I've seen in the archives of this list that the VE2ZAZ design makes a
number of simplification/performance tradeoffs.

Is there a design I haven't listed which is "better" than the others?
I'm quite familiar with microcontrollers, FPGAs, spinning my own
PCBs, etc, so I'll roll my own if I have to, but I'd prefer to build
a variation on someone's tried and true design.

I'm aware of products like the Fury, but I'd like something I could tinker
with, and the cost is hard to justify for a hobbyist.

Scott
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[SAIDJACK]

 
In a message dated 12/11/2007 03:11:24 Pacific Standard Time,  
[EMAIL PROTECTED] writes:

>To  check correct operation vary the Fury EFC output from 0 to 5V with
>the  desired offset at U3 +ve input.

>Bruce



Hi gents,
 
this can be done manually with the command serv:coarsedac [0,255]
 
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] John Vig elected President of IEEE

[Chuck Harris]

Star Office is a stable version of OpenOffice.org that has
support from Sun.  OpenOffice.org is the bleeding edge
development version.

OpenOffice.org appears to open it just fine, but when you look
closely, you notice that most screens overlap their page numbers,
and some table entries are larger than the space alloted.

Rob Kimberley wrote:
> I just opened this with Star Office 8 without a hitch. Star Office 8 is free
> from Google by the way using their excellent Google Pack
> http://pack.google.com/intl/en-gb/pack_installer_new.html?hl=en-gb&gl=uk&ciN
> um=11 
> 
> Also exported it out successfully to PDF. 
> 
> I'm running Windows XP, so have all the usual MS True type fonts installed.
> I'm guessing that anyone trying Open Office from a Linux distribution would
> have problems.  Free SUSE 10.3 (which I have as a dual boot on one of my
> machines) has the option to download and install the MS font set, so that
> should solve the problem. Not sure about other Linux flavours. 
> 
> Looks like John Vig used Arial for most of it anyway.

The problem is MS has all of their font sizes wrong.  What they call a 12 pt
is really smaller than a true 12 pt... [well, either MS has it wrong, or the
rest of the world has it wrong.]

-Chuck Harris

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] John Vig elected President of IEEE

[Rob Kimberley]

I just opened this with Star Office 8 without a hitch. Star Office 8 is free
from Google by the way using their excellent Google Pack
http://pack.google.com/intl/en-gb/pack_installer_new.html?hl=en-gb&gl=uk&ciN
um=11 

Also exported it out successfully to PDF. 

I'm running Windows XP, so have all the usual MS True type fonts installed.
I'm guessing that anyone trying Open Office from a Linux distribution would
have problems.  Free SUSE 10.3 (which I have as a dual boot on one of my
machines) has the option to download and install the MS font set, so that
should solve the problem. Not sure about other Linux flavours. 

Looks like John Vig used Arial for most of it anyway.

Rob K

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Chuck Harris
Sent: 10 December 2007 19:36
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] John Vig elected President of IEEE

Poul-Henning Kamp wrote:
> In message <[EMAIL PROTECTED]>, "Tom Van Baak" writes:
> 
>> Right click and SaveAs this 7.4 MB PPT file to your PC:
>>
>> Quartz Resonator & Oscillator Tutorial
>> http://www.ieee-uffc.org/freqcontrol/tutorials/vig3/vig3.ppt
>>
>> Then open the 298 page document with PowerPoint and
>> print as "note pages".
> 
> I wish somebody could make a pdf of that, I don't have (and don't
> want!) access to Powerpoint[1].

Sure you do, it is called: "OpenOffice.org" ;-)

-Chuck Harris

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[xaos]

Bruce Griffiths wrote:
> George
>
> In the JFET frequency doubler:
> 1) Surely the 50 ohms should be is series with the the voltage source V3
> for the simulation?
>   
Correct. I did a cut and paste "without rotate" there.
> 2) Usually a 1:4 impedance ratio step up transformer on the input is
> about right with a similar transformer used to step down the output
> (perhaps an even higher impedance ratio transformer (8:1, 9:1?? may be
> better). The maximum turns ratio depends somewhat on the maximum
> allowable drain voltage swing which in turn is limited by the drain
> supply voltage.
>   
I will re-run with the this in mind and will repost.
> In the voltage offset circuit:
>
> 1) The junction of R9 and R12 should be connected to the offset source
> (+5V??).
>   
This is what I didn't get about the original circuit.  I was scratching 
my head as to the purpose of a variable R9 when
the only value that made sense was when it was set to the "0" position.

> I dont understand what the 7812 does in this circuit.
>   
It was there in the original circuit so I modeled accordingly. Actually 
I ran some simulations with PS voltage variation
to see the effect as well. In that case I removed the 7812.
> Isolation amplifier looks OK.
>
> Bruce
>   
This is a very nice design and the AC analysis shows a bandpass around 
10 MHz with 20 MHz BW.

The only issue I see there is that it needs 50 parts of 6 different values.

This might be difficult to implement on a small board and would be prone 
to error for people trying to
assemble their own board.

The way I see the final product is a bare board and possibly a kit. It 
has to be easy to assemble and minimize
errors.

Actually, I was looking at the isolation amplifier provided in the C.M. 
Felton Paper:

http://www.darksmile.net/ee/Superimposing_Low-Phase-Noise_Low-Drift_Instrumentation_Techniques_On_RF_Design.pdf

It is relatively simple and would use similar devices as the Frequency 
doubler.

I will upload more info as I compile it.

George

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[Bruce Griffiths]

xaos wrote:
> Hello Everyone,
>
> I have been running simulations of different parts of the Fury Interface 
> board.
>
> Here are the results so far.
>
> http://www.darksmile.net/ee/index.html
>
> Your feedback is most welcome.
>
> -George
>
>   
George

A more versatile EFC circuit that allows independent adjustment of EFC
span and offset is possible if an additional opamp is used.
A 2x differential amplifier translates the Fury EFC output to either
{-10V, 0V] or [0V, +10V] depending on its input connections,  a second
opamp inverts a  +5Vreference to produce a -5V source offset source, and
a third opamp configured as an inverting opamp scales the EFC range and
adds it to the offset to produce the required EFC range to suit the OCXO
in use. An OCXO  EFC range anywhere between -10V and + 10V can be
accommodated by selecting a couple of resistors  combined with a set of
jumpers.
If you want the circuit schematic I can produce it by around 1300 UTC
tomorrow.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Fury Interface Board simulation results

[Bruce Griffiths]

xaos wrote:
> Hello Everyone,
>
> I have been running simulations of different parts of the Fury Interface 
> board.
>
> Here are the results so far.
>
> http://www.darksmile.net/ee/index.html
>
> Your feedback is most welcome.
>
> -George
>
>   
George

The Fury EFC output range is [0, +5V]
The 10811A, 10544A have an EFC range of [-5V, +5V]
other OCXOs may have an EFC input range of [-10V ,0V], [0,+10V], [-10V,
+10V] or even [+2V, +8V] etc.

If the  circuit is changed so that R1 = R10 = 20K then

Range
[-10V, 0V]   U3A +ve input = 0 V.
[-5V, +5V]   U3A +ve input = +2.5V.
[0V, +10V]  U3A +ve input = +5V.
for a [-10V, +10V] range then R1=R10= 40K, U3A +ve input = +5V.
To check correct operation vary the Fury EFC output from 0 to 5V with
the desired offset at U3 +ve input.

Bruce

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] WIRED Time Nuts

[Marco IK1ODO -2]

At 08.20 11/12/2007, you wrote:
>Hi John & Rick,
>
>Looks like Quinn's WIRED magazine time-nuts article was just released...

Very nice article. A lot of mad guys out there :-) !

73 - Marco IK1ODO / AI4YF




___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Fury Latest Firmware

[SAIDJACK]

Hello Fellow Time Nuts,
 
we placed the latest firmware version 1.16 onto the _www.jackson-labs.com_ 
(http://www.jackson-labs.com)  website under  the support tab.
 
This version fixes the issue that the Lock LED does not go on if the OCXO  
(which is missing from the PCB of course) is < 35 Degrees C.

It also adds the external 1PPS input FailSafe feature (please see the  
quick-start guide online), and fixes various other minor issues.
 
We hope this helps, and please do let us know if you find any issues, bugs,  
errata etc!
 
Thanks again, especially to CH for reporting the LED problem,
bye,
Said



**See AOL's top rated recipes 
(http://food.aol.com/top-rated-recipes?NCID=aoltop000304)
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.