Re: [time-nuts] GPSDO Alternatives

[David]

On Fri, 07 Dec 2012 17:50:55 -0500, "Charles P. Steinmetz"
 wrote:

>John wrote:
>
>>What's *really* interesting, though, is the idea that collectively 
>>we might develop some standard measurement protocols that would be 
>>reproducible in a number of (amateur) labs.
>
>I agree, but I didn't dare to dream so large when I wrote:
>
>>>  From my perspective, the most interesting development would be an offer
>>>by someone with a very well equipped lab to test any DIY GPSDO with a
>>>consistent protocol and publish the results.  That way, we could all see
>>>how the various approaches compare with respect to the characteristics
>>>that are most important to each of us.
>
>At bottom, any such testing requires (i) a comparison standard at 
>least as good (and hopefully at least somewhat better) than the DUT 
>at all taus and offsets (which may, in reality, be several standards, 
>each doing part of that job), (ii) a reliable TIC (and, potentially 
>usefully, frequency counter) that can exploit the stability of the 
>comparison standard, and (iii) the capability to process the raw data 
>to produce meaningful information.  [Additionally, to characterize 
>poor-signal behavior one would presumably use attenuators and a 
>well-situated antenna.  Some may not have good antenna sites to begin 
>with, and in any case, it would be hard to standardize the signal 
>strength between locations.]
>
>My thoughts were (1) for many (most?) of the people who would want to 
>build a DIY GPSDO, it would likely be their first "really good" 
>standard, and therefore their best; and (2) the range of 
>TICs/frequency counters owned by the target base is so wide, and 
>covers such a large range of capabilities (to say nothing of whether 
>any given counter is in good repair and being used to best 
>advantage), that obtaining comparable results from one amateur lab to 
>another would be just as much if not more dependent on the individual 
>counters involved than on the GPSDOs under test.
>
>However, that is no reason not to push forward with standardized 
>measurement protocols, which would focus all of us on what the 
>relevant desiderata are and how to measure them.

For myself:

1. My current lack a comparison standard is the reason I would design
and build a GPSDO.  At best I might buy a used rubidium oscillator at
some point.   People talk about good deals on Thunderbolts but I have
yet to see one.  It seems peak Thunderbolt passed before I was
seriously looking.

2.  So far my best universal counter is a rebuilt Racal Dana 1992 with
a TCXO but it lacks GPIB.  It might be easier and cheaper for me to
duplicate my GPSDO phase detector and add a counter chain and trigger
so it can make and report its own time interval measurements against a
secondary asynchronous source but that would hardly be reproducible by
a third party.

3.  I am less interested in this since I will be at the mercy of
whatever timing GPS I use and my current antenna environment.

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Re: [time-nuts] GPSDO Alternatives - Bert's boards

[WB6BNQ]

Hello Bert,

The boards look nice but tell me nothing of the circuitry.  How about sending 
the schematics ??  That way I
can appreciate what it is that you have.

BillWB6BNQ
p.s.  By the way, what ever happen with that DMTD you were going to produce 
about three years ago ?


ewkeh...@aol.com wrote:

> Attached is my latest ExpresPCB layout of a GPSDO. A clear  understanding
> of the GPS limitations, a goal as to what I want to control ,focus  on
> attainability, reproducibility KISS, cost and tests of partials on  
> development
> boards and what you see if you download the ExpessPCB software is on  the
> right the saw tooth correction, in the middle the analog board with opto
> isolation to prevent ground loop and on the right the actual GPSDO.  This
> particular unit also allows you to link a 20 Hz offset FRS-C (part of my dual
> mixer) to my house reference. Total material cost depending how many boards  
> one
> buys is below $ 40. I will include this particular board along with other
> designs on my next order and subsequently cut with a sheer.
> The board on the right could be used by itself with minor  modifications to
> directly drive a FE 5680 if some one would step up to the task.  Total cost
> below $ 15. I use the analog board, which by the way is the most  expensive
> since it has a LTC 1655 and REF 02.
> No dither 16 bits, dither 18 bits and depending on loop time,  clock
> frequency range starting at 3 E-9 and resolution up to 6  E-16.
> Again I am only interested in to controlling a Rb which gives  me way more
> flexibility, the Rb's are either modified with a 10811 or in  one case with
> the M1000 and in the case of the FE 5680 a MV89 with a separate  analog loop.
> And in all cases the RB is temperature  controlled.
> All this based on over 10 years of work with the Shera  controller,
> exclusively controlling Rb's.
> Bert Kehren
> One more thought you may want to look at a 1 $ gate array for  all your
> timing issues. Simplifies the work dramatically. With the long loop  times
> associated with Rb and high sample rate, 100 psec. are no  problem.
>
>   
> Name: Shera 3 board.pcb
>Shera 3 board.pcbType: PCB Wizard Document 
> (application/x-unknown-content-type-PCBWizard.Document)
> Encoding: base64
>
>   
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Re: [time-nuts] GPSDO Alternatives

[Charles P. Steinmetz]

John wrote:

What's *really* interesting, though, is the idea that collectively 
we might develop some standard measurement protocols that would be 
reproducible in a number of (amateur) labs.


I agree, but I didn't dare to dream so large when I wrote:


 From my perspective, the most interesting development would be an offer
by someone with a very well equipped lab to test any DIY GPSDO with a
consistent protocol and publish the results.  That way, we could all see
how the various approaches compare with respect to the characteristics
that are most important to each of us.


At bottom, any such testing requires (i) a comparison standard at 
least as good (and hopefully at least somewhat better) than the DUT 
at all taus and offsets (which may, in reality, be several standards, 
each doing part of that job), (ii) a reliable TIC (and, potentially 
usefully, frequency counter) that can exploit the stability of the 
comparison standard, and (iii) the capability to process the raw data 
to produce meaningful information.  [Additionally, to characterize 
poor-signal behavior one would presumably use attenuators and a 
well-situated antenna.  Some may not have good antenna sites to begin 
with, and in any case, it would be hard to standardize the signal 
strength between locations.]


My thoughts were (1) for many (most?) of the people who would want to 
build a DIY GPSDO, it would likely be their first "really good" 
standard, and therefore their best; and (2) the range of 
TICs/frequency counters owned by the target base is so wide, and 
covers such a large range of capabilities (to say nothing of whether 
any given counter is in good repair and being used to best 
advantage), that obtaining comparable results from one amateur lab to 
another would be just as much if not more dependent on the individual 
counters involved than on the GPSDOs under test.


However, that is no reason not to push forward with standardized 
measurement protocols, which would focus all of us on what the 
relevant desiderata are and how to measure them.


Best regards,

Charles








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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

At least one should compare similar to better than approaches. This is a
multi year design. Pick a goal first, then try to fit a specific approach to
the goal. If the approach makes sense, move on with the design.

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of paul swed
Sent: Friday, December 07, 2012 1:38 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Bob
Yes would agree these are the attributes of a solution thats interesting.
Numbers of folks have created solutions over the years. But the
reference architecture should be as good as or better then the tried and
true tool we have like the HP 38XX or Tbolt. Otherwise is just another
GPSDO.
Regards
Paul
WB8TSL

On Fri, Dec 7, 2012 at 12:15 PM, Bob Camp  wrote:

> Hi
>
> Without some qualifier on "how good", we all will be talking about
> hourglasses and cesium standards at the same time. That makes sorting
> things
> out a bit difficult. It may get you into building a "controlled hourglass"
> that's less accurate than a free running $10 wrist watch.
>
> So far the only suggestion of a "how good" has been TBolt performance. At
> least that's how this started out.
>
> Building a "cpu only" GPSDO can be done with a big enough chip. If you are
> limited to clip leads to wire it up, the cost advantage over a TBolt may
> not
> be there. That makes the issue of significant performance loss a very real
> issue.
>
> --
>
> Just as surplus deals on TBolts come and go, so do deals on OCXO's and
> GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70
> that they sell for today? Is the GPS in the junk box (that I paid $200
for)
> free because it's sitting there? Let's not even wonder if any of the stuff
> works...
>
> For the sake of moving this forward, I'll suggest that half the fair cost
> of
> a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or
> what ever) is split $100 for the OCXO plus GPS and $100 for:
>
> 1) The nice shielded case it's all in
> 2) The connectors
> 3) The onboard power regulation and filtering
> 4) The communications in and out of it
> 5) The 10 MHz and PPS buffering and generation
> 6) The PC board it's all built on
> 7) Putting it all together
> 8) Programming all the parts in there
> 9) Testing it and troubleshooting it
> 10) The smarts to get it to do what it does
>
> I'm sure we could spend at least a year splitting hairs on that division
of
> costs :)
>
> To "win" the hourglass vs cesium fair trade proposition you need to come
up
> with a gizmo that:
>
> 1) Does 1-10 above
> 2) Works with just a GPS and OCXO added.
> 3) Costs less than $100
> 4) Works as well as a TBolt
> 5) Has a Lady Heather like monitor program to go with it
>
> For the sake of eliminating crazy GPS cards. Let's say you also need a
> source where we can buy both the OCXO and GPS used for less than $100.
>
> If you want to factor in lower performance, I'll grant a waver for the
fact
> that you can average multiple gizmos and the result will get better by the
> square root of the number of gizmos. If it's half as good as a $200 TBolt
> it
> needs to be 1/4 the price.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Jim Lux
> Sent: Friday, December 07, 2012 10:13 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives (GLUE)
>
> On 12/6/12 5:01 PM, Bob Camp wrote:
> > Hi
> >
> > The solution to the problem is well known in several forms. Cost is
below
> $5 for pretty much all of them. No need to re-invent the wheel. The gotcha
> is that you can't do it 100% with internal CPU peripherals. You will need
> *some* glue.
> >
> >
> I think that's the interesting aspect of this discussion (because it
> mirrors many similar such discussions I've had over the years)..
>
> The challenge is not in building a GPSDO.. there's tons of ways to do
> that at minimal hardware cost..
>
> The challenge is "how do you do it without using any additional glue
> logic or hardware"  That is, given things you can buy off the shelf, and
> no hardware work other than fabricating cables or soldering a wire or
> two, what can you do inexpensively.
>
>
>
>
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> time-nuts mailing list -- time-nuts@febo.com
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and fo

Re: [time-nuts] GPSDO Alternatives

[paul swed]

Bob
Yes would agree these are the attributes of a solution thats interesting.
Numbers of folks have created solutions over the years. But the
reference architecture should be as good as or better then the tried and
true tool we have like the HP 38XX or Tbolt. Otherwise is just another
GPSDO.
Regards
Paul
WB8TSL

On Fri, Dec 7, 2012 at 12:15 PM, Bob Camp  wrote:

> Hi
>
> Without some qualifier on "how good", we all will be talking about
> hourglasses and cesium standards at the same time. That makes sorting
> things
> out a bit difficult. It may get you into building a "controlled hourglass"
> that's less accurate than a free running $10 wrist watch.
>
> So far the only suggestion of a "how good" has been TBolt performance. At
> least that's how this started out.
>
> Building a "cpu only" GPSDO can be done with a big enough chip. If you are
> limited to clip leads to wire it up, the cost advantage over a TBolt may
> not
> be there. That makes the issue of significant performance loss a very real
> issue.
>
> --
>
> Just as surplus deals on TBolts come and go, so do deals on OCXO's and
> GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70
> that they sell for today? Is the GPS in the junk box (that I paid $200 for)
> free because it's sitting there? Let's not even wonder if any of the stuff
> works...
>
> For the sake of moving this forward, I'll suggest that half the fair cost
> of
> a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or
> what ever) is split $100 for the OCXO plus GPS and $100 for:
>
> 1) The nice shielded case it's all in
> 2) The connectors
> 3) The onboard power regulation and filtering
> 4) The communications in and out of it
> 5) The 10 MHz and PPS buffering and generation
> 6) The PC board it's all built on
> 7) Putting it all together
> 8) Programming all the parts in there
> 9) Testing it and troubleshooting it
> 10) The smarts to get it to do what it does
>
> I'm sure we could spend at least a year splitting hairs on that division of
> costs :)
>
> To "win" the hourglass vs cesium fair trade proposition you need to come up
> with a gizmo that:
>
> 1) Does 1-10 above
> 2) Works with just a GPS and OCXO added.
> 3) Costs less than $100
> 4) Works as well as a TBolt
> 5) Has a Lady Heather like monitor program to go with it
>
> For the sake of eliminating crazy GPS cards. Let's say you also need a
> source where we can buy both the OCXO and GPS used for less than $100.
>
> If you want to factor in lower performance, I'll grant a waver for the fact
> that you can average multiple gizmos and the result will get better by the
> square root of the number of gizmos. If it's half as good as a $200 TBolt
> it
> needs to be 1/4 the price.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Jim Lux
> Sent: Friday, December 07, 2012 10:13 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives (GLUE)
>
> On 12/6/12 5:01 PM, Bob Camp wrote:
> > Hi
> >
> > The solution to the problem is well known in several forms. Cost is below
> $5 for pretty much all of them. No need to re-invent the wheel. The gotcha
> is that you can't do it 100% with internal CPU peripherals. You will need
> *some* glue.
> >
> >
> I think that's the interesting aspect of this discussion (because it
> mirrors many similar such discussions I've had over the years)..
>
> The challenge is not in building a GPSDO.. there's tons of ways to do
> that at minimal hardware cost..
>
> The challenge is "how do you do it without using any additional glue
> logic or hardware"  That is, given things you can buy off the shelf, and
> no hardware work other than fabricating cables or soldering a wire or
> two, what can you do inexpensively.
>
>
>
>
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> and follow the instructions there.
>
>
>
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Re: [time-nuts] GPSDO Alternatives

[Don Latham]

but we could use a less expensive one. a simple light interruptor senses
the end of flow, a robust servo turns over the hourglass for the next
cycle. our favorite arduino counts seconds from the gps, and adjusts the
turnover appropriately. If magnetite sand is used, an external magnetic
field can provide rate correction for phase control rather than
frequency control?
A smaller version would generate the perfect 3 minute egg.
o gosh maybe this thread is petering out in my head
don L

Bob Camp
> Hi
>
> That is an impressive hourglass. In the context of the thought
> experiment "swap offer" - no, mine is not a work of art. It's only value
> is as a time keeper.
>
> Bob
>
> On Dec 6, 2012, at 10:37 PM, DaveH  wrote:
>
>> If you had an Ikepod, I might be interested.
>>
>> http://www.ablogtowatch.com/ikepod-hourglass-time-for-art/
>>
>> http://www.hodinkee.com/blog/2011/3/29/the-ikepod-hourglass-by-marc-newson-q
>> uite-possibly-the-coole.html
>>
>> http://www.ikepod.com/
>>
>> Dave
>>
>>> -Original Message-
>>> From: time-nuts-boun...@febo.com
>>> [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
>>> Sent: Thursday, December 06, 2012 18:23
>>> To: Discussion of precise time and frequency measurement
>>> Subject: Re: [time-nuts] GPSDO Alternatives
>>>
>>> Hi
>>>
>>> Here's another way to look at this:
>>>
>>> An hourglass full of sand (with some attention) and a cesium
>>> standard are both ways to answer the question "what time is
>>> it?". Let's say you need a new $40,000 tube replacement in
>>> your 5371 and management asks "what else can we do?".  An
>>> hour glass  is indeed a "something else we can do". They both
>>> deliver an answer to the time of day question. Without
>>> defining what you actually *need* to do, they are both valid
>>> approaches.
>>>
>>> The problem comes when you look at the $40,000 repair charge
>>> and decide that building an hour glass is a lot cheaper.
>>> While that's true, it's far from the whole story. One way to
>>> quickly work some of this out is a simple swap proposition.
>>> Would anybody on the list trade their (working) cesium for my
>>> (working) hourglass? I'll pay shipping..
>>>
>>> Bob
>>>
>>> On Dec 6, 2012, at 9:03 PM, Mark Sims  wrote:
>>>
>>>>
>>>> I think only TIMER2 on the AVR has the clk/4 limitation.
>>> The other timers can count at full speed.I know that I
>>> have counted at 8-12 MHz before...
>>>>
>>>>
>>>> ___
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>>>
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>>> and follow the instructions there.
>>
>>
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>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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Re: [time-nuts] GPSDO Alternatives

[Tom Miller]

And then it becomes popular and guess what happens to the price?


Tom

- Original Message - 
From: "Bob Camp" 
To: "'Discussion of precise time and frequency measurement'" 


Sent: Friday, December 07, 2012 12:15 PM
Subject: Re: [time-nuts] GPSDO Alternatives


To "win" the hourglass vs cesium fair trade proposition you need to come up
with a gizmo that:

1) Does 1-10 above
2) Works with just a GPS and OCXO added.
3) Costs less than $100
4) Works as well as a TBolt
5) Has a Lady Heather like monitor program to go with it

For the sake of eliminating crazy GPS cards. Let's say you also need a
source where we can buy both the OCXO and GPS used for less than $100.

If you want to factor in lower performance, I'll grant a waver for the fact
that you can average multiple gizmos and the result will get better by the
square root of the number of gizmos. If it's half as good as a $200 TBolt it
needs to be 1/4 the price.

Bob



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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Without some qualifier on "how good", we all will be talking about
hourglasses and cesium standards at the same time. That makes sorting things
out a bit difficult. It may get you into building a "controlled hourglass"
that's less accurate than a free running $10 wrist watch. 

So far the only suggestion of a "how good" has been TBolt performance. At
least that's how this started out. 

Building a "cpu only" GPSDO can be done with a big enough chip. If you are
limited to clip leads to wire it up, the cost advantage over a TBolt may not
be there. That makes the issue of significant performance loss a very real
issue. 

--

Just as surplus deals on TBolts come and go, so do deals on OCXO's and
GPS's. Do I price the OCXO at the $13 that I once saw it for, or the $70
that they sell for today? Is the GPS in the junk box (that I paid $200 for)
free because it's sitting there? Let's not even wonder if any of the stuff
works...

For the sake of moving this forward, I'll suggest that half the fair cost of
a (working) TBolt is the OCXO and the GPS. Put another way, your $200 (or
what ever) is split $100 for the OCXO plus GPS and $100 for:

1) The nice shielded case it's all in
2) The connectors
3) The onboard power regulation and filtering
4) The communications in and out of it
5) The 10 MHz and PPS buffering and generation
6) The PC board it's all built on
7) Putting it all together
8) Programming all the parts in there
9) Testing it and troubleshooting it
10) The smarts to get it to do what it does

I'm sure we could spend at least a year splitting hairs on that division of
costs :)

To "win" the hourglass vs cesium fair trade proposition you need to come up
with a gizmo that: 

1) Does 1-10 above
2) Works with just a GPS and OCXO added.
3) Costs less than $100
4) Works as well as a TBolt
5) Has a Lady Heather like monitor program to go with it

For the sake of eliminating crazy GPS cards. Let's say you also need a
source where we can buy both the OCXO and GPS used for less than $100.

If you want to factor in lower performance, I'll grant a waver for the fact
that you can average multiple gizmos and the result will get better by the
square root of the number of gizmos. If it's half as good as a $200 TBolt it
needs to be 1/4 the price.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Jim Lux
Sent: Friday, December 07, 2012 10:13 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives (GLUE)

On 12/6/12 5:01 PM, Bob Camp wrote:
> Hi
>
> The solution to the problem is well known in several forms. Cost is below
$5 for pretty much all of them. No need to re-invent the wheel. The gotcha
is that you can't do it 100% with internal CPU peripherals. You will need
*some* glue.
>
>
I think that's the interesting aspect of this discussion (because it 
mirrors many similar such discussions I've had over the years)..

The challenge is not in building a GPSDO.. there's tons of ways to do 
that at minimal hardware cost..

The challenge is "how do you do it without using any additional glue 
logic or hardware"  That is, given things you can buy off the shelf, and 
no hardware work other than fabricating cables or soldering a wire or 
two, what can you do inexpensively.




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Re: [time-nuts] GPSDO Alternatives (GLUE)

[paul swed]

Jim right on target for my 2 cents,
Simple is often hard.
Regards
Paul
WB8TSL

On Fri, Dec 7, 2012 at 10:12 AM, Jim Lux  wrote:

> On 12/6/12 5:01 PM, Bob Camp wrote:
>
>> Hi
>>
>> The solution to the problem is well known in several forms. Cost is below
>> $5 for pretty much all of them. No need to re-invent the wheel. The gotcha
>> is that you can't do it 100% with internal CPU peripherals. You will need
>> *some* glue.
>>
>>
>>  I think that's the interesting aspect of this discussion (because it
> mirrors many similar such discussions I've had over the years)..
>
> The challenge is not in building a GPSDO.. there's tons of ways to do that
> at minimal hardware cost..
>
> The challenge is "how do you do it without using any additional glue logic
> or hardware"  That is, given things you can buy off the shelf, and no
> hardware work other than fabricating cables or soldering a wire or two,
> what can you do inexpensively.
>
>
>
>
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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/6/12 11:20 PM, Don Latham wrote:

Good thought, Bob. AD9548 $27, eval board a whopping $250, get a
thunderbolt :-). The eval board has a lot of SMA's on it...



This is a general problem with eval boards these days.. They provide a 
lot of functionality on the board to make it easy to evaluate the chip 
(USB interfaces, buffer memories, etc.)  but that makes it hard to use 
the eval board as a sort of glorified chip carrier.


For instance, all those nice serial interface ADC and DAC parts.. it 
would be nice to have a little board with the converter, power supply 
filtering and maybe an opamp buffer, and bring the serial interface pins 
to the edge where you could just wire it to something like a PIC eval 
board or Arduino or parallel printer port.  But no.. they have a weird 
connector that goes to a mother board with a fancy preprogrammed micro 
and dual port memory and stuff.. all so you can just hook up a signal 
generator and capture samples to run FFTs to duplicate the databook graphs.



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Re: [time-nuts] GPSDO Alternatives (GLUE)

[Jim Lux]

On 12/6/12 5:01 PM, Bob Camp wrote:

Hi

The solution to the problem is well known in several forms. Cost is below $5 
for pretty much all of them. No need to re-invent the wheel. The gotcha is that 
you can't do it 100% with internal CPU peripherals. You will need *some* glue.


I think that's the interesting aspect of this discussion (because it 
mirrors many similar such discussions I've had over the years)..


The challenge is not in building a GPSDO.. there's tons of ways to do 
that at minimal hardware cost..


The challenge is "how do you do it without using any additional glue 
logic or hardware"  That is, given things you can buy off the shelf, and 
no hardware work other than fabricating cables or soldering a wire or 
two, what can you do inexpensively.





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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/6/12 11:12 PM, Hal Murray wrote:






Suppose you just implement a simple bang-bang control.

Suppose the EFC is 1 volt and the frequency is correct but the GPSDO
phase is a bit early relative to the GPS PPS.  So the FF says early
and the software says go-faster.  That keeps happening for a while,
the frequency keeps getting faster and faster.  Finally, the GPSDO
PPS catches up with the GPS PPS, but now it's frequency is way fast.
The FF says go slower, so the control software starts dropping the
EFC.  But the frequency is still way too high so the error is still
increasing.  After a while the frequency gets low enough so the
PPS/phase error starts catching up.  Eventually the PPS error crosses
over, but by then the frequency offset is way way low.  ...  Isn't
that cyclic pattern stable?

Is there a simple tweak to break that loop?  Do you first have to
recognize that you are in that mode?  If so, how?  ...


yes.. what you've described is essentially a first order control loop. 
You can add higher order terms (e.g. integral or derivative) so that you 
don't get overshoot.







I might be able to do fix that in software by looking at the times
when things change state.  Suppose it's 193 seconds between the first
early and the last early and that the EFC went from X to Y.  I think
that's enough info to work out the crossover point and work back to
the desired EFC.


Yes.. that's another approach.. you figure out what the model is, and 
solve backwards.





But that all sounds too complicated.  What would hardware-only guys
do with a 1 bit A/D?






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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/6/12 1:56 PM, Bob Camp wrote:

Hi

The single best thing about a TBolt is Lady Heather.

Consider how many years it's taken to get it to where it is today. Consider
how many people have worked extensively on it. It's a wonderful thing to
have available.

Could you make a homebrew gizmo look "just like a TBolt"? Sure you could. It
might well take you forever to do all the reverse engineering, validation,
and testing, but it can be done. I'd guess it would take less time to
re-write a version of LH from scratch




Of course, the process of experimenting and trying to duplicate the 
Tbolt is fairly educational.  It touches a lot of interesting areas in 
RF design and metrology, as well as software algorithms.  One might do 
it for the same reason that someone builds a fusor in their garage. 
There are easier ways to get neutrons, but building a fusor is a nice 
combination of learning about high vacuum, high voltage, nuclear physics 
and metrology, etc.


Both are a heck of a lot cheaper than building and flying a CubeSat, for 
instance.






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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

That is an impressive hourglass. In the context of the thought experiment "swap 
offer" - no, mine is not a work of art. It's only value is as a time keeper. 

Bob

On Dec 6, 2012, at 10:37 PM, DaveH  wrote:

> If you had an Ikepod, I might be interested.
> 
> http://www.ablogtowatch.com/ikepod-hourglass-time-for-art/
> 
> http://www.hodinkee.com/blog/2011/3/29/the-ikepod-hourglass-by-marc-newson-q
> uite-possibly-the-coole.html
> 
> http://www.ikepod.com/
> 
> Dave 
> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com 
>> [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
>> Sent: Thursday, December 06, 2012 18:23
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] GPSDO Alternatives
>> 
>> Hi
>> 
>> Here's another way to look at this:
>> 
>> An hourglass full of sand (with some attention) and a cesium 
>> standard are both ways to answer the question "what time is 
>> it?". Let's say you need a new $40,000 tube replacement in 
>> your 5371 and management asks "what else can we do?".  An 
>> hour glass  is indeed a "something else we can do". They both 
>> deliver an answer to the time of day question. Without 
>> defining what you actually *need* to do, they are both valid 
>> approaches. 
>> 
>> The problem comes when you look at the $40,000 repair charge 
>> and decide that building an hour glass is a lot cheaper. 
>> While that's true, it's far from the whole story. One way to 
>> quickly work some of this out is a simple swap proposition. 
>> Would anybody on the list trade their (working) cesium for my 
>> (working) hourglass? I'll pay shipping..
>> 
>> Bob
>> 
>> On Dec 6, 2012, at 9:03 PM, Mark Sims  wrote:
>> 
>>> 
>>> I think only TIMER2 on the AVR has the clk/4 limitation.   
>> The other timers can count at full speed.I know that I 
>> have counted at 8-12 MHz before...
>>> 
>>>   
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

In this case it's very much a "you get what you pay for" sort of thing. You are 
indeed comparing an hourglass to a cesium standard.

Bob

On Dec 7, 2012, at 2:20 AM, "Don Latham"  wrote:

> Good thought, Bob. AD9548 $27, eval board a whopping $250, get a
> thunderbolt :-). The eval board has a lot of SMA's on it...
> Don L
> Bob Camp
>> Hi
>> 
>> If all you want is a "something" locked to a GPS:
>> 
>> Take the pps from the GPS and hook it to an AD9548. You probably will
>> need a 50 cent CPU to set up the registers.  No muss, no fuss,  nothing
>> to invent or design.
>> 
>> Weather it does what you need to do is an entirely different question.
>> Without a defined objective / need / performance goal this could go on
>> for a couple hundred years…..
>> 
>> Bob
>> 
>> On Dec 6, 2012, at 7:43 PM, Chris Albertson 
>> wrote:
>> 
>>> What if the OCXO had a sine wave output and then you used the PPS
>>> leading
>>> edge to gate the sine wave to a sample and hold.  then the sample is
>>> measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is
>>> it
>>> 8-bits.  The problem is the required speed of the sample and hold,
>>> maybe
>>> not easy to build
>>> --
>>> 
>>> Chris Albertson
>>> Redondo Beach, California
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>> 
>> 
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>> 
> 
> 
> -- 
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
> 
> 
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

You are driving an integrator (the OCXO). You want a very stable voltage on the 
EFC to get the loop to close. A PWM is as simple a model for a 1 bit D/A as 
any. One bit A/D's are a feedback on a 1 bit D/A. You do some stuff to move the 
noise around and to get it all to work.  

Bob

On Dec 7, 2012, at 2:12 AM, Hal Murray  wrote:

> 
>> The output from a OCXO is divided down and then the phase of the divided
>> down 10MHz RF is compared to the PPS and you don't need to even know the how
>> far apart they are.  All you need to know is "led or lag"  just a one bit
>> answer.   An XOR gate or a flip flop can tell you that. 
> 
> Does a 1 bit A/D work?  Is there a good web page discussing this aspect?  Am 
> I just confused?What question should I be asking?   ...  Can somebody give me 
> a circuit or (pseudo) code so I can simulate things?
> 
> I'm far from a PLL wizard.  I think the catch in this case is that the EFC 
> controls the frequency and what you are measuring is the phase, the integral 
> of the frequency.
> 
> Suppose you just implement a simple bang-bang control.
> 
> Suppose the EFC is 1 volt and the frequency is correct but the GPSDO phase is 
> a bit early relative to the GPS PPS.  So the FF says early and the software 
> says go-faster.  That keeps happening for a while, the frequency keeps 
> getting faster and faster.  Finally, the GPSDO PPS catches up with the GPS 
> PPS, but now it's frequency is way fast.  The FF says go slower, so the 
> control software starts dropping the EFC.  But the frequency is still way too 
> high so the error is still increasing.  After a while the frequency gets low 
> enough so the PPS/phase error starts catching up.  Eventually the PPS error 
> crosses over, but by then the frequency offset is way way low.  ...  Isn't 
> that cyclic pattern stable?
> 
> Is there a simple tweak to break that loop?  Do you first have to recognize 
> that you are in that mode?  If so, how?  ...
> 
> I might be able to do fix that in software by looking at the times when 
> things change state.  Suppose it's 193 seconds between the first early and 
> the last early and that the EFC went from X to Y.  I think that's enough info 
> to work out the crossover point and work back to the desired EFC.
> 
> But that all sounds too complicated.  What would hardware-only guys do with a 
> 1 bit A/D?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

To make things play nice, you would like to have the timer counters reset at a 
specified point. That way the math all works out nicely.

Bob

On Dec 7, 2012, at 12:18 AM, Hal Murray  wrote:

> 
> li...@rtty.us said:
>> That would be an input capture rather than an interrupt.
> 
> Thanks.  Yes, that's the term I was trying to remember.
> 
> 
> li...@rtty.us said:
>> To be useful, you need an input capture that:
>> 1) Runs at a fast enough clock (1 GHz would be nice)
>> 2) Has enough bits to get to 1 pps (say 32 bits)
>> 3) Has a built in period set, so the hardware works without a lot of silly 
>> stuff 
> 
> What do you mean by "period set"?
> 
> (I did a bit of googling, but didn't hit anything close to pay dirt.)
> 
> My expectation is that the counter/timer just counts on the local/CPU clock 
> or some sub-multiple of that.  When the external signal makes a low-to-high 
> transition, the value in the counter is copied into a holding register and 
> sets a status bit that may generate an interrupt.  The counter just keeps 
> counting through overflows and such.
> 
> --
> 
> The enough-bits from [2] above can be partially implemented in software.  
> When the counter overflows, it sets a status bit and maybe generates an 
> interrupt.  The software keeps the high bits in memory.  When it sees that 
> status bit, it bumps that counter.
> 
> Getting everything right is not simple.
> 
> There is a standard recipe for reading a hardware counter that lives in two 
> registers.  You read high, low, high.  If the two high readings match, the 
> answer is (either) high and low.  If not, try again.
> 
> Some hardware supports a hack to latch the high when you read the low.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Don Latham]

Good thought, Bob. AD9548 $27, eval board a whopping $250, get a
thunderbolt :-). The eval board has a lot of SMA's on it...
Don L
Bob Camp
> Hi
>
> If all you want is a "something" locked to a GPS:
>
> Take the pps from the GPS and hook it to an AD9548. You probably will
> need a 50 cent CPU to set up the registers.  No muss, no fuss,  nothing
> to invent or design.
>
> Weather it does what you need to do is an entirely different question.
> Without a defined objective / need / performance goal this could go on
> for a couple hundred years…..
>
> Bob
>
> On Dec 6, 2012, at 7:43 PM, Chris Albertson 
> wrote:
>
>> What if the OCXO had a sine wave output and then you used the PPS
>> leading
>> edge to gate the sine wave to a sample and hold.  then the sample is
>> measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is
>> it
>> 8-bits.  The problem is the required speed of the sample and hold,
>> maybe
>> not easy to build
>> --
>>
>> Chris Albertson
>> Redondo Beach, California
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>


-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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Re: [time-nuts] GPSDO Alternatives

[SAIDJACK]

Hello,
 
metastability is not an issue in this type of application, nor can it be  
avoided since we have two different clock domains.
 
It would only shift the capture point by one counter clock cycle back or  
forth if the edge happens right on the transition point. At that  point we 
have 50% uncertainty where it should fall anyway's, so the  best one could do 
is switch back and forth between the two counter values  creating an average 
of half way between these two counter points!
 
Also the GPS sawtooth will create enough jitter on the  capture pin to 
avoid staying in metastability for more than one  pulse.
 
Metastability is an issue for applications that need to be bit-accurate,  
such as trying to capture a serial datastream etc. A 1PPS capture application 
in  a GPSDO is not a bit-accurate affair, it is a heavily averaged (low 
pass  filtered) system so statistics kick in.
 
The real problem of the LPC932 capture system is that the resolution goes  
from 33ns on the counter to something around 200ns because of the pin 
clocking  the input FF at 5MHz... its a waste of possible resolution on that 
chip. 
 200ns is quite a low resolution for a GPSDO, but there are ways to improve 
this  resolution through dithering for example.
 
bye,
Said
 
 
 
 
In a message dated 12/6/2012 20:35:35 Pacific Standard Time,  
hmur...@megapathdsl.net writes:

saidj...@aol.com said:
> Then setting up a test system we  noted that the timer can capture with
> 32MHz resolution which is good  enough for a low-cost GPSDO 
implementation,
> but that they gated the  input pin through a flip-flop running at CPU core
> speed, which was  around 6MHz if I remember correctly. 

davidwh...@gmail.com  said:
> The ATmega328 apparently has something similar going on since  the 
datasheet
> says that the maximum external asynchronous clock  frequency is 1/4 of the
> CPU frequency.  That is why I suggested  synchronously clocking the CPU
> directly from the OCXO.  Atmel's  datasheet is annoyingly vague about some
> matters and I assume the  capture input works like it should. 

You have to do something  appropriate when multiple clocks are involved or 
you 
get metastability  issues.

I think the 1/4 limit is to allow the external pin to be used  to clock the 
counter.  If you run the external signal through the  standard pair of FFs 
to 
get a signal that is synchronous to your clock,  1/4 guarantees that you 
will 
see all transitions.  At 1/2, with the  duty cycle slightly off 50-50, you 
might end up with hanging-bridge type  cases where the output of the 
synchronizer always sees the same  level.

Actually, metastability is hard to hit.  Most  "metastability" issues are 
really just setup/hold  bugs.


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Re: [time-nuts] GPSDO Alternatives

[Hal Murray]

> The output from a OCXO is divided down and then the phase of the divided
> down 10MHz RF is compared to the PPS and you don't need to even know the how
> far apart they are.  All you need to know is "led or lag"  just a one bit
> answer.   An XOR gate or a flip flop can tell you that. 

Does a 1 bit A/D work?  Is there a good web page discussing this aspect?  Am 
I just confused?What question should I be asking?   ...  Can somebody give me 
a circuit or (pseudo) code so I can simulate things?

I'm far from a PLL wizard.  I think the catch in this case is that the EFC 
controls the frequency and what you are measuring is the phase, the integral 
of the frequency.

Suppose you just implement a simple bang-bang control.

Suppose the EFC is 1 volt and the frequency is correct but the GPSDO phase is a 
bit early relative to the GPS PPS.  So the FF says early and the software says 
go-faster.  That keeps happening for a while, the frequency keeps getting 
faster and faster.  Finally, the GPSDO PPS catches up with the GPS PPS, but now 
it's frequency is way fast.  The FF says go slower, so the control software 
starts dropping the EFC.  But the frequency is still way too high so the error 
is still increasing.  After a while the frequency gets low enough so the 
PPS/phase error starts catching up.  Eventually the PPS error crosses over, but 
by then the frequency offset is way way low.  ...  Isn't that cyclic pattern 
stable?

Is there a simple tweak to break that loop?  Do you first have to recognize 
that you are in that mode?  If so, how?  ...

I might be able to do fix that in software by looking at the times when things 
change state.  Suppose it's 193 seconds between the first early and the last 
early and that the EFC went from X to Y.  I think that's enough info to work 
out the crossover point and work back to the desired EFC.

But that all sounds too complicated.  What would hardware-only guys do with a 1 
bit A/D?



-- 
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Re: [time-nuts] GPSDO Alternatives

[Hal Murray]

li...@rtty.us said:
> That would be an input capture rather than an interrupt.

Thanks.  Yes, that's the term I was trying to remember.


li...@rtty.us said:
> To be useful, you need an input capture that:
> 1) Runs at a fast enough clock (1 GHz would be nice)
> 2) Has enough bits to get to 1 pps (say 32 bits)
> 3) Has a built in period set, so the hardware works without a lot of silly 
> stuff 

What do you mean by "period set"?

(I did a bit of googling, but didn't hit anything close to pay dirt.)

My expectation is that the counter/timer just counts on the local/CPU clock 
or some sub-multiple of that.  When the external signal makes a low-to-high 
transition, the value in the counter is copied into a holding register and 
sets a status bit that may generate an interrupt.  The counter just keeps 
counting through overflows and such.

--

The enough-bits from [2] above can be partially implemented in software.  
When the counter overflows, it sets a status bit and maybe generates an 
interrupt.  The software keeps the high bits in memory.  When it sees that 
status bit, it bumps that counter.

Getting everything right is not simple.

There is a standard recipe for reading a hardware counter that lives in two 
registers.  You read high, low, high.  If the two high readings match, the 
answer is (either) high and low.  If not, try again.

Some hardware supports a hack to latch the high when you read the low.


-- 
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Re: [time-nuts] GPSDO Alternatives

[Hal Murray]

saidj...@aol.com said:
> Then setting up a test system we noted that the timer can capture with
> 32MHz resolution which is good enough for a low-cost GPSDO implementation,
> but that they gated the input pin through a flip-flop running at CPU core
> speed, which was around 6MHz if I remember correctly. 

davidwh...@gmail.com said:
> The ATmega328 apparently has something similar going on since the datasheet
> says that the maximum external asynchronous clock frequency is 1/4 of the
> CPU frequency.  That is why I suggested synchronously clocking the CPU
> directly from the OCXO.  Atmel's datasheet is annoyingly vague about some
> matters and I assume the capture input works like it should. 

You have to do something appropriate when multiple clocks are involved or you 
get metastability issues.

I think the 1/4 limit is to allow the external pin to be used to clock the 
counter.  If you run the external signal through the standard pair of FFs to 
get a signal that is synchronous to your clock, 1/4 guarantees that you will 
see all transitions.  At 1/2, with the duty cycle slightly off 50-50, you 
might end up with hanging-bridge type cases where the output of the 
synchronizer always sees the same level.

Actually, metastability is hard to hit.  Most "metastability" issues are 
really just setup/hold bugs.


davidwh...@gmail.com said:
> I have also heard about many low cost ARM microcontrollers suffering from
> problems similar to the one you describe.  Apparently the ones that use an
> asynchronous interface between the CPU and peripherals either have slow
> interfaces or suffer from some odd problems.

Bingo.

Many years ago, I found that sort of bug in an ARM chip.  I forget which one. 
 It needed 2 crystals, one at 32 KHz and one at xx MHz.  The CPU could run at 
32 KHz, or PLLed to the fast crystal, or sleep.  While running at 32 KHz, it 
could turn on the fast osc and setup the PLL.  Reading the 32 KHz counter 
while running off the fast crystal would occasionally get bogus results.


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Re: [time-nuts] GPSDO Alternatives

[DaveH]

If you had an Ikepod, I might be interested.

http://www.ablogtowatch.com/ikepod-hourglass-time-for-art/

http://www.hodinkee.com/blog/2011/3/29/the-ikepod-hourglass-by-marc-newson-q
uite-possibly-the-coole.html

http://www.ikepod.com/

Dave 

> -Original Message-
> From: time-nuts-boun...@febo.com 
> [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
> Sent: Thursday, December 06, 2012 18:23
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPSDO Alternatives
> 
> Hi
> 
> Here's another way to look at this:
> 
> An hourglass full of sand (with some attention) and a cesium 
> standard are both ways to answer the question "what time is 
> it?". Let's say you need a new $40,000 tube replacement in 
> your 5371 and management asks "what else can we do?".  An 
> hour glass  is indeed a "something else we can do". They both 
> deliver an answer to the time of day question. Without 
> defining what you actually *need* to do, they are both valid 
> approaches. 
> 
> The problem comes when you look at the $40,000 repair charge 
> and decide that building an hour glass is a lot cheaper. 
> While that's true, it's far from the whole story. One way to 
> quickly work some of this out is a simple swap proposition. 
> Would anybody on the list trade their (working) cesium for my 
> (working) hourglass? I'll pay shipping..
> 
> Bob
> 
> On Dec 6, 2012, at 9:03 PM, Mark Sims  wrote:
> 
> > 
> > I think only TIMER2 on the AVR has the clk/4 limitation.   
> The other timers can count at full speed.I know that I 
> have counted at 8-12 MHz before...
> > 
> >   
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Re: [time-nuts] GPSDO Alternatives

[dlewis6767]

Perhaps this is all coming full circle.  As more experience herein shows use of 
the 1-pps from the gps module is valid, that opens the door to many more cheap 
GPS modules available than just a few that have 10 KHz also.

Some of the low-cost GPS modules have the 1-pps associated with UTC (accurate), 
...many do not.  It depends on what their original purpose was.  Many were used 
for 'cheap' navigation devices, ...not intended for timing.  Accuracy is on the 
order 10 to even 100 microseconds.

It then seems to me a simpler state machine, driven by the gps 1pps could be 
designed.  It could run at 2hz and have 6-to-10 states, as many as needed.  
Need to get out the old Karnaugh map book.

  a.. Reset, open counter gate, count two seconds, close counter gate, load dac 
with overflow/underflow, switch dac output to EVC cap, start over.

Don






--
From: "Chris Albertson" 
Sent: Thursday, December 06, 2012 6:30 PM
To: "Discussion of precise time and frequency measurement" 
Subject: Re: [time-nuts] GPSDO Alternatives

> On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767  wrote:
> 
>> could you not add just a little 'glue' outside the uP to relieve it a tad.
>>
>> Let the GPS' 1pps gate some ttl counters and then read for overflow or
>> underflow after xxx seconds.  Have the uP determine  dac correction setting
>> back to the TXCO.
>>
>>
> That is why my first post was to ask "What is the simplest phase defector
> that can work?"   I think you only need a one-bit counter.  A flip-flop
> will do that.   The FF is a classic phase detector used in many PLL
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[David]

The other timer on the ATmega328 lacks an input capture pin and
register.  I did not check all of the different AVR microcontrollers
used in Arduinos.

On Fri, 7 Dec 2012 02:03:39 +, Mark Sims 
wrote:

>I think only TIMER2 on the AVR has the clk/4 limitation.   The other timers 
>can count at full speed.I know that I have counted at 8-12 MHz before...

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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Here's another way to look at this:

An hourglass full of sand (with some attention) and a cesium standard are both 
ways to answer the question "what time is it?". Let's say you need a new 
$40,000 tube replacement in your 5371 and management asks "what else can we 
do?".  An hour glass  is indeed a "something else we can do". They both deliver 
an answer to the time of day question. Without defining what you actually 
*need* to do, they are both valid approaches. 

The problem comes when you look at the $40,000 repair charge and decide that 
building an hour glass is a lot cheaper. While that's true, it's far from the 
whole story. One way to quickly work some of this out is a simple swap 
proposition. Would anybody on the list trade their (working) cesium for my 
(working) hourglass? I'll pay shipping….

Bob

On Dec 6, 2012, at 9:03 PM, Mark Sims  wrote:

> 
> I think only TIMER2 on the AVR has the clk/4 limitation.   The other timers 
> can count at full speed.I know that I have counted at 8-12 MHz before...
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

If all you want is a "something" locked to a GPS:

Take the pps from the GPS and hook it to an AD9548. You probably will need a 50 
cent CPU to set up the registers.  No muss, no fuss,  nothing to invent or 
design.

Weather it does what you need to do is an entirely different question. Without 
a defined objective / need / performance goal this could go on for a couple 
hundred years…..

Bob

On Dec 6, 2012, at 7:43 PM, Chris Albertson  wrote:

> What if the OCXO had a sine wave output and then you used the PPS leading
> edge to gate the sine wave to a sample and hold.  then the sample is
> measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is it
> 8-bits.  The problem is the required speed of the sample and hold, maybe
> not easy to build
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

PSoC's are another attractive possibility that suffers from the same basic 
"re-clock everything" flaw. Lots of time down the drain there….

Bob

On Dec 6, 2012, at 8:22 PM, saidj...@aol.com wrote:

> David,
> 
> The NXP LPC932 processor series are very cheap and small, and we got very  
> excited to see timers running at up to 32MHz internally if I remember  
> correctly.
> 
> Then setting up a test system we noted that the timer can capture with  
> 32MHz resolution which is good enough for a low-cost GPSDO implementation, 
> but  
> that they gated the input pin through a flip-flop running at CPU core 
> speed,  which was around 6MHz if I remember correctly.
> 
> DAA. So all that fast timer resolution goes out the door by gating the  
> input pin instead of using non-gated inputs for the timer functions.
> 
> It does work however, in the end we made that processor do the chores in  
> our quite old and discontinued FireFox GPSDO circuit. TVB has some plots  on 
> his website for that unit I think, and its quite surprising what type of  
> stability we achieved with that little 8 bit bugger back then.
> 
> bye,
> Said
> 
> 
> In a message dated 12/6/2012 16:00:27 Pacific Standard Time,  
> davidwh...@gmail.com writes:
> 
> You can  use the ATmega328 16 bit timer/counter in input capture mode
> to count the  number of 10 MHz OCXO cycles per pulse per second period
> to a resolution of  100ns but there are some problems:
> 
> The ATmega328 16 bit timer/counter  external clock is limited to 1/4 of
> the CPU frequency with an asynchronous  source so the 10 MHz OCXO would
> need to be divided down which would further  limit performance and
> require an external divider.  Modifying the  Aruino board to use the 10
> MHz OCXO in place of the CPU clock solves that  problem.
> 
> Then operating the counter/timer in input capture mode with  the GPS
> pulse per second signal connected to the input capture pin would  allow
> almost Shera like performance.  The timing resolution would be  2.4
> times lower (and not asynchronous) limiting performance over  short
> time spans.
> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Unless you really want to go crazy with measuring very long delays, you do 
indeed want to align the pps from your OCXO with the pps from your GPS.

Bob

On Dec 6, 2012, at 8:48 PM, "Don Latham"  wrote:

> Chris: yes, dividing would have to be done. Doesn't TVB have a simple
> divider block?
> You don't really have to "close" the difference, just maintain it?
> Don L
> Chris Albertson
>> You'd have to seriously divide down the output from the 10MHz OCXO if
>> you
>> were going to use it as an interrupt.  Maybe to divide by 10,000? and
>> even
>> at the higher clock rate you'd still have poor resolution.
>> 
>> I image each interrupt handler would sample some internal counter and
>> the
>> background task would look at the delta between the two and adjust the
>> DAC
>> to drive the OCXO to close the difference.   The resolution would be
>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
>> second period it might wrk well enough.  I can't know without doing a
>> more
>> detailed design
>> 
>> 
>> On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
>> 
>>> Chris:
>>> 
 The question I have again is about a simple phase detector.
>>> 
>>> I did ask if the arduino interrupt ports could be used as a phase
>>> detector; one on the GPS and one on the OXCO. Too much jitter? If the
>>> 12
>>> MHz clock is too slow, would an 80 MHz clock ARM arduino style
>>> processor
>>> work? I'm simply too new at this to decide.
>>> 
>>> Don
>>> 
>>> --
>>> "Neither the voice of authority nor the weight of reason and argument
>>> are as significant as experiment, for thence comes quiet to the mind."
>>> De Erroribus Medicorum, R. Bacon, 13th century.
>>> "If you don't know what it is, don't poke it."
>>> Ghost in the Shell
>>> 
>>> 
>>> Dr. Don Latham AJ7LL
>>> Six Mile Systems LLP
>>> 17850 Six Mile Road
>>> POB 134
>>> Huson, MT, 59846
>>> VOX 406-626-4304
>>> www.lightningforensics.com
>>> www.sixmilesystems.com
>>> 
>>> 
>>> 
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>>> and follow the instructions there.
>>> 
>> 
>> 
>> 
>> --
>> 
>> Chris Albertson
>> Redondo Beach, California
>> ___
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>> and follow the instructions there.
>> 
> 
> 
> -- 
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
> 
> 
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The Shera counter is not running in the same fashion you would be running an 
input capture pin. 

Bob

On Dec 6, 2012, at 8:45 PM, David  wrote:

> Sorry.  The Shera counter is 16 bits and not 12 bits but that does not
> change what I posted.
> 
> On Thu, 06 Dec 2012 19:17:48 -0600, David 
> wrote:
> 
>> It is not a 16 bit capture and it does not run at 1/4 the clock rate.
>> 
>> The Shera uses a 12 bit counter to capture the phase difference
>> between the OCXO frequency divided by 16 and GPS pulse per second
>> output to a resolution of about 42ns.
>> 
>> What I suggested effectively captures the same phase difference but
>> divides the OCXO by 65536 and only has a resolution of 100ns.  The
>> OCXO division is just conceptual though as it comes from the 16 bit
>> timer/counter overflow internal to the microcontroller so in practice,
>> the timer/counter is arbitrary length with an interrupt about every
>> 6.5ms doing the housekeeping for the extra bits.  It directly measures
>> the pulse per second period to a resolution of 100ns using the OCXO as
>> a clock.  If a 20 MHz OCXO was used (limited by the maximum clock
>> frequency of the microcontroller), then the resolution would be 50ns.
>> 
>> That is not how I plan on designing my own GPSDO which has taken a
>> significant turn from what I posted about here some time ago but I
>> have stopped discussing that until I have some results to share.
> 
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Re: [time-nuts] GPSDO Alternatives

[Don Latham]

Chris: yes, dividing would have to be done. Doesn't TVB have a simple
divider block?
You don't really have to "close" the difference, just maintain it?
Don L
Chris Albertson
> You'd have to seriously divide down the output from the 10MHz OCXO if
> you
> were going to use it as an interrupt.  Maybe to divide by 10,000? and
> even
> at the higher clock rate you'd still have poor resolution.
>
> I image each interrupt handler would sample some internal counter and
> the
> background task would look at the delta between the two and adjust the
> DAC
> to drive the OCXO to close the difference.   The resolution would be
> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
> second period it might wrk well enough.  I can't know without doing a
> more
> detailed design
>
>
> On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
>
>> Chris:
>>
>> > The question I have again is about a simple phase detector.
>>
>> I did ask if the arduino interrupt ports could be used as a phase
>> detector; one on the GPS and one on the OXCO. Too much jitter? If the
>> 12
>> MHz clock is too slow, would an 80 MHz clock ARM arduino style
>> processor
>> work? I'm simply too new at this to decide.
>>
>> Don
>>
>> --
>> "Neither the voice of authority nor the weight of reason and argument
>> are as significant as experiment, for thence comes quiet to the mind."
>> De Erroribus Medicorum, R. Bacon, 13th century.
>> "If you don't know what it is, don't poke it."
>> Ghost in the Shell
>>
>>
>> Dr. Don Latham AJ7LL
>> Six Mile Systems LLP
>> 17850 Six Mile Road
>> POB 134
>> Huson, MT, 59846
>> VOX 406-626-4304
>> www.lightningforensics.com
>> www.sixmilesystems.com
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
> ___
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>


-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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Re: [time-nuts] GPSDO Alternatives

[David]

Sorry.  The Shera counter is 16 bits and not 12 bits but that does not
change what I posted.

On Thu, 06 Dec 2012 19:17:48 -0600, David 
wrote:

>It is not a 16 bit capture and it does not run at 1/4 the clock rate.
>
>The Shera uses a 12 bit counter to capture the phase difference
>between the OCXO frequency divided by 16 and GPS pulse per second
>output to a resolution of about 42ns.
>
>What I suggested effectively captures the same phase difference but
>divides the OCXO by 65536 and only has a resolution of 100ns.  The
>OCXO division is just conceptual though as it comes from the 16 bit
>timer/counter overflow internal to the microcontroller so in practice,
>the timer/counter is arbitrary length with an interrupt about every
>6.5ms doing the housekeeping for the extra bits.  It directly measures
>the pulse per second period to a resolution of 100ns using the OCXO as
>a clock.  If a 20 MHz OCXO was used (limited by the maximum clock
>frequency of the microcontroller), then the resolution would be 50ns.
>
>That is not how I plan on designing my own GPSDO which has taken a
>significant turn from what I posted about here some time ago but I
>have stopped discussing that until I have some results to share.

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Re: [time-nuts] GPSDO Alternatives

[David]

The ATmega328 apparently has something similar going on since the
datasheet says that the maximum external asynchronous clock frequency
is 1/4 of the CPU frequency.  That is why I suggested synchronously
clocking the CPU directly from the OCXO.  Atmel's datasheet is
annoyingly vague about some matters and I assume the capture input
works like it should.

I have also heard about many low cost ARM microcontrollers suffering
from problems similar to the one you describe.  Apparently the ones
that use an asynchronous interface between the CPU and peripherals
either have slow interfaces or suffer from some odd problems.

It is not *that* difficult to get to 10ns using a 100Mhz phase locked
clock (or even faster) in timer/counter applications using discrete
logic support but in the case of GPSDO design, I believe better
results can be obtained without so much brute force.

I am one of those weirdos who likes ECL whether integrated or
discrete.

On Thu, 6 Dec 2012 20:22:58 -0500 (EST), saidj...@aol.com wrote:

>David,
> 
>The NXP LPC932 processor series are very cheap and small, and we got very  
>excited to see timers running at up to 32MHz internally if I remember  
>correctly.
> 
>Then setting up a test system we noted that the timer can capture with  
>32MHz resolution which is good enough for a low-cost GPSDO implementation, but 
> 
>that they gated the input pin through a flip-flop running at CPU core 
>speed,  which was around 6MHz if I remember correctly.
> 
>DAA. So all that fast timer resolution goes out the door by gating the  
>input pin instead of using non-gated inputs for the timer functions.
> 
>It does work however, in the end we made that processor do the chores in  
>our quite old and discontinued FireFox GPSDO circuit. TVB has some plots  on 
>his website for that unit I think, and its quite surprising what type of  
>stability we achieved with that little 8 bit bugger back then.
> 
>bye,
>Said
> 
> 
>In a message dated 12/6/2012 16:00:27 Pacific Standard Time,  
>davidwh...@gmail.com writes:
>
>You can  use the ATmega328 16 bit timer/counter in input capture mode
>to count the  number of 10 MHz OCXO cycles per pulse per second period
>to a resolution of  100ns but there are some problems:
>
>The ATmega328 16 bit timer/counter  external clock is limited to 1/4 of
>the CPU frequency with an asynchronous  source so the 10 MHz OCXO would
>need to be divided down which would further  limit performance and
>require an external divider.  Modifying the  Aruino board to use the 10
>MHz OCXO in place of the CPU clock solves that  problem.
>
>Then operating the counter/timer in input capture mode with  the GPS
>pulse per second signal connected to the input capture pin would  allow
>almost Shera like performance.  The timing resolution would be  2.4
>times lower (and not asynchronous) limiting performance over  short
>time spans.
>
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Re: [time-nuts] GPSDO Alternatives

[David]

There are lots of sampling ADCs which will support that type of
operation directly or you can easily design and build a sampling phase
detector but that all involves significant extra circuitry outside of
the microcontroller.

Take a look at the Racal Dana 1992 reference frequency multiplier
option (the schematic is on page 7-33 of the service manual) for an
example of a sampling phase detector used in a similar application.

On Thu, 6 Dec 2012 16:43:26 -0800, Chris Albertson
 wrote:

>What if the OCXO had a sine wave output and then you used the PPS leading
>edge to gate the sine wave to a sample and hold.  then the sample is
>measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is it
>8-bits.  The problem is the required speed of the sample and hold, maybe
>not easy to build

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Re: [time-nuts] GPSDO Alternatives

[SAIDJACK]

David,
 
The NXP LPC932 processor series are very cheap and small, and we got very  
excited to see timers running at up to 32MHz internally if I remember  
correctly.
 
Then setting up a test system we noted that the timer can capture with  
32MHz resolution which is good enough for a low-cost GPSDO implementation, but  
that they gated the input pin through a flip-flop running at CPU core 
speed,  which was around 6MHz if I remember correctly.
 
DAA. So all that fast timer resolution goes out the door by gating the  
input pin instead of using non-gated inputs for the timer functions.
 
It does work however, in the end we made that processor do the chores in  
our quite old and discontinued FireFox GPSDO circuit. TVB has some plots  on 
his website for that unit I think, and its quite surprising what type of  
stability we achieved with that little 8 bit bugger back then.
 
bye,
Said
 
 
In a message dated 12/6/2012 16:00:27 Pacific Standard Time,  
davidwh...@gmail.com writes:

You can  use the ATmega328 16 bit timer/counter in input capture mode
to count the  number of 10 MHz OCXO cycles per pulse per second period
to a resolution of  100ns but there are some problems:

The ATmega328 16 bit timer/counter  external clock is limited to 1/4 of
the CPU frequency with an asynchronous  source so the 10 MHz OCXO would
need to be divided down which would further  limit performance and
require an external divider.  Modifying the  Aruino board to use the 10
MHz OCXO in place of the CPU clock solves that  problem.

Then operating the counter/timer in input capture mode with  the GPS
pulse per second signal connected to the input capture pin would  allow
almost Shera like performance.  The timing resolution would be  2.4
times lower (and not asynchronous) limiting performance over  short
time spans.

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Re: [time-nuts] GPSDO Alternatives

[David]

It is not a 16 bit capture and it does not run at 1/4 the clock rate.

The Shera uses a 12 bit counter to capture the phase difference
between the OCXO frequency divided by 16 and GPS pulse per second
output to a resolution of about 42ns.

What I suggested effectively captures the same phase difference but
divides the OCXO by 65536 and only has a resolution of 100ns.  The
OCXO division is just conceptual though as it comes from the 16 bit
timer/counter overflow internal to the microcontroller so in practice,
the timer/counter is arbitrary length with an interrupt about every
6.5ms doing the housekeeping for the extra bits.  It directly measures
the pulse per second period to a resolution of 100ns using the OCXO as
a clock.  If a 20 MHz OCXO was used (limited by the maximum clock
frequency of the microcontroller), then the resolution would be 50ns.

That is not how I plan on designing my own GPSDO which has taken a
significant turn from what I posted about here some time ago but I
have stopped discussing that until I have some results to share.

On Thu, 6 Dec 2012 19:34:08 -0500, Bob Camp  wrote:

>Hi
>
>Again, the math is pretty simple. 
>
>A 16 bit capture running at a 1/4 clock is not going to get you very near a 
>Shera. It's even further from the more modern "enhanced Shera" designs. 
>
>Bob
>
>On Dec 6, 2012, at 6:59 PM, David  wrote:
>
>> You can use the ATmega328 16 bit timer/counter in input capture mode
>> to count the number of 10 MHz OCXO cycles per pulse per second period
>> to a resolution of 100ns but there are some problems:
>> 
>> The ATmega328 16 bit timer/counter external clock is limited to 1/4 of
>> the CPU frequency with an asynchronous source so the 10 MHz OCXO would
>> need to be divided down which would further limit performance and
>> require an external divider.  Modifying the Aruino board to use the 10
>> MHz OCXO in place of the CPU clock solves that problem.
>> 
>> Then operating the counter/timer in input capture mode with the GPS
>> pulse per second signal connected to the input capture pin would allow
>> almost Shera like performance.  The timing resolution would be 2.4
>> times lower (and not asynchronous) limiting performance over short
>> time spans.
>> 
>> On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson
>>  wrote:
>> 
>>> You'd have to seriously divide down the output from the 10MHz OCXO if you
>>> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>>> at the higher clock rate you'd still have poor resolution.
>>> 
>>> I image each interrupt handler would sample some internal counter and the
>>> background task would look at the delta between the two and adjust the DAC
>>> to drive the OCXO to close the difference.   The resolution would be
>>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
>>> second period it might wrk well enough.  I can't know without doing a more
>>> detailed design
>>> 
>>> 
>>> On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
>>> 
 Chris:
 
> The question I have again is about a simple phase detector.
 
 I did ask if the arduino interrupt ports could be used as a phase
 detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
 MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
 work? I'm simply too new at this to decide.
 
 Don
>> 
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The solution to the problem is well known in several forms. Cost is below $5 
for pretty much all of them. No need to re-invent the wheel. The gotcha is that 
you can't do it 100% with internal CPU peripherals. You will need *some* glue. 

Bob

On Dec 6, 2012, at 7:43 PM, Chris Albertson  wrote:

> What if the OCXO had a sine wave output and then you used the PPS leading
> edge to gate the sine wave to a sample and hold.  then the sample is
> measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is it
> 8-bits.  The problem is the required speed of the sample and hold, maybe
> not easy to build
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

What if the OCXO had a sine wave output and then you used the PPS leading
edge to gate the sine wave to a sample and hold.  then the sample is
measured by the Arduino's ADC?  I think(?) you get a 10-bit ADC or is it
8-bits.  The problem is the required speed of the sample and hold, maybe
not easy to build
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The simplest phase detector does indeed work. It just does not work very well. 
Not correcting the oscillator at all works, you will have time and frequency to 
some level of accuracy. Not correcting it at all is a whole lot cheaper and 
simpler.

Bob

On Dec 6, 2012, at 7:30 PM, Chris Albertson  wrote:

> On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767  wrote:
> 
>> could you not add just a little 'glue' outside the uP to relieve it a tad.
>> 
>> Let the GPS' 1pps gate some ttl counters and then read for overflow or
>> underflow after xxx seconds.  Have the uP determine  dac correction setting
>> back to the TXCO.
>> 
>> 
> That is why my first post was to ask "What is the simplest phase defector
> that can work?"   I think you only need a one-bit counter.  A flip-flop
> will do that.   The FF is a classic phase detector used in many PLL
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Again, the math is pretty simple. 

A 16 bit capture running at a 1/4 clock is not going to get you very near a 
Shera. It's even further from the more modern "enhanced Shera" designs. 

Bob

On Dec 6, 2012, at 6:59 PM, David  wrote:

> You can use the ATmega328 16 bit timer/counter in input capture mode
> to count the number of 10 MHz OCXO cycles per pulse per second period
> to a resolution of 100ns but there are some problems:
> 
> The ATmega328 16 bit timer/counter external clock is limited to 1/4 of
> the CPU frequency with an asynchronous source so the 10 MHz OCXO would
> need to be divided down which would further limit performance and
> require an external divider.  Modifying the Aruino board to use the 10
> MHz OCXO in place of the CPU clock solves that problem.
> 
> Then operating the counter/timer in input capture mode with the GPS
> pulse per second signal connected to the input capture pin would allow
> almost Shera like performance.  The timing resolution would be 2.4
> times lower (and not asynchronous) limiting performance over short
> time spans.
> 
> On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson
>  wrote:
> 
>> You'd have to seriously divide down the output from the 10MHz OCXO if you
>> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>> at the higher clock rate you'd still have poor resolution.
>> 
>> I image each interrupt handler would sample some internal counter and the
>> background task would look at the delta between the two and adjust the DAC
>> to drive the OCXO to close the difference.   The resolution would be
>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
>> second period it might wrk well enough.  I can't know without doing a more
>> detailed design
>> 
>> 
>> On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
>> 
>>> Chris:
>>> 
 The question I have again is about a simple phase detector.
>>> 
>>> I did ask if the arduino interrupt ports could be used as a phase
>>> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
>>> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
>>> work? I'm simply too new at this to decide.
>>> 
>>> Don
> 
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

On Thu, Dec 6, 2012 at 4:09 PM, dlewis6767  wrote:

> could you not add just a little 'glue' outside the uP to relieve it a tad.
>
> Let the GPS' 1pps gate some ttl counters and then read for overflow or
> underflow after xxx seconds.  Have the uP determine  dac correction setting
> back to the TXCO.
>
>
That is why my first post was to ask "What is the simplest phase defector
that can work?"   I think you only need a one-bit counter.  A flip-flop
will do that.   The FF is a classic phase detector used in many PLL
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[dlewis6767]

could you not add just a little 'glue' outside the uP to relieve it a tad.

Let the GPS' 1pps gate some ttl counters and then read for overflow or 
underflow after xxx seconds.  Have the uP determine  dac correction setting 
back to the TXCO.


-Don






--
From: "Bob Camp" 
Sent: Thursday, December 06, 2012 5:55 PM
To: "Discussion of precise time and frequency measurement" 


Subject: Re: [time-nuts] GPSDO Alternatives


Hi

To be useful, you need an input capture that:

1) Runs at a fast enough clock (1 GHz would be nice)
2) Has enough bits to get to 1 pps (say 32 bits)
3) Has a built in period set, so the hardware works without a lot of silly 
stuff


Often you find parts that will do some of the above, but not all. 16 bit 
captures running off of a "few MHz" clock are pretty common. Some (but not 
all) ARM's have 32 bit captures that run off of 10's of MHz clocks and 
have the ability to set the period.


Bob


On Dec 6, 2012, at 6:34 PM, Lizeth Norman  wrote:


Bob et al:
Have been following this thread with interest.
Re the input capture versus interrupt, I do believe (at least the 2560
does this) that you can do both. It's been a while since I looked. a
look at the hardware manual. Was interested in this feature to do
hardware timing.
Norm

On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp  wrote:

Hi

That would be an input capture rather than an interrupt.

Bob

On Dec 6, 2012, at 6:16 PM, Hal Murray  wrote:



albertson.ch...@gmail.com said:
You'd have to seriously divide down the output from the 10MHz OCXO if 
you
were going to use it as an interrupt.  Maybe to divide by 10,000? and 
even

at the higher clock rate you'd still have poor resolution.


I image each interrupt handler would sample some internal counter and 
the
background task would look at the delta between the two and adjust the 
DAC

to drive the OCXO to close the difference.   The resolution would be
(maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 
second
period it might wrk well enough.  I can't know without doing a more 
detailed

design


Do some of the counter/timer modules have an option to run the counter 
off an
internal clock and copy the value into another register on an external 
signal?


That avoids any interrupt latency.




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Re: [time-nuts] GPSDO Alternatives

[David]

You can use the ATmega328 16 bit timer/counter in input capture mode
to count the number of 10 MHz OCXO cycles per pulse per second period
to a resolution of 100ns but there are some problems:

The ATmega328 16 bit timer/counter external clock is limited to 1/4 of
the CPU frequency with an asynchronous source so the 10 MHz OCXO would
need to be divided down which would further limit performance and
require an external divider.  Modifying the Aruino board to use the 10
MHz OCXO in place of the CPU clock solves that problem.

Then operating the counter/timer in input capture mode with the GPS
pulse per second signal connected to the input capture pin would allow
almost Shera like performance.  The timing resolution would be 2.4
times lower (and not asynchronous) limiting performance over short
time spans.

On Thu, 6 Dec 2012 14:57:19 -0800, Chris Albertson
 wrote:

>You'd have to seriously divide down the output from the 10MHz OCXO if you
>were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>at the higher clock rate you'd still have poor resolution.
>
>I image each interrupt handler would sample some internal counter and the
>background task would look at the delta between the two and adjust the DAC
>to drive the OCXO to close the difference.   The resolution would be
>(maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
>second period it might wrk well enough.  I can't know without doing a more
>detailed design
>
>
>On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
>
>> Chris:
>>
>> > The question I have again is about a simple phase detector.
>>
>> I did ask if the arduino interrupt ports could be used as a phase
>> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
>> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
>> work? I'm simply too new at this to decide.
>>
>> Don

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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

To be useful, you need an input capture that:

1) Runs at a fast enough clock (1 GHz would be nice)
2) Has enough bits to get to 1 pps (say 32 bits)
3) Has a built in period set, so the hardware works without a lot of silly stuff

Often you find parts that will do some of the above, but not all. 16 bit 
captures running off of a "few MHz" clock are pretty common. Some (but not all) 
ARM's have 32 bit captures that run off of 10's of MHz clocks and have the 
ability to set the period.

Bob


On Dec 6, 2012, at 6:34 PM, Lizeth Norman  wrote:

> Bob et al:
> Have been following this thread with interest.
> Re the input capture versus interrupt, I do believe (at least the 2560
> does this) that you can do both. It's been a while since I looked. a
> look at the hardware manual. Was interested in this feature to do
> hardware timing.
> Norm
> 
> On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp  wrote:
>> Hi
>> 
>> That would be an input capture rather than an interrupt.
>> 
>> Bob
>> 
>> On Dec 6, 2012, at 6:16 PM, Hal Murray  wrote:
>> 
>>> 
>>> albertson.ch...@gmail.com said:
 You'd have to seriously divide down the output from the 10MHz OCXO if you
 were going to use it as an interrupt.  Maybe to divide by 10,000? and even
 at the higher clock rate you'd still have poor resolution.
>>> 
 I image each interrupt handler would sample some internal counter and the
 background task would look at the delta between the two and adjust the DAC
 to drive the OCXO to close the difference.   The resolution would be
 (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 
 second
 period it might wrk well enough.  I can't know without doing a more 
 detailed
 design
>>> 
>>> Do some of the counter/timer modules have an option to run the counter off 
>>> an
>>> internal clock and copy the value into another register on an external 
>>> signal?
>>> 
>>> That avoids any interrupt latency.
>>> 
>>> 
>>> 
>>> 
>>> --
>>> These are my opinions.  I hate spam.
>>> 
>>> 
>>> 
>>> 
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>> 
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Re: [time-nuts] GPSDO Alternatives

[Lizeth Norman]

Bob et al:
Have been following this thread with interest.
Re the input capture versus interrupt, I do believe (at least the 2560
does this) that you can do both. It's been a while since I looked. a
look at the hardware manual. Was interested in this feature to do
hardware timing.
Norm

On Thu, Dec 6, 2012 at 6:25 PM, Bob Camp  wrote:
> Hi
>
> That would be an input capture rather than an interrupt.
>
> Bob
>
> On Dec 6, 2012, at 6:16 PM, Hal Murray  wrote:
>
>>
>> albertson.ch...@gmail.com said:
>>> You'd have to seriously divide down the output from the 10MHz OCXO if you
>>> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>>> at the higher clock rate you'd still have poor resolution.
>>
>>> I image each interrupt handler would sample some internal counter and the
>>> background task would look at the delta between the two and adjust the DAC
>>> to drive the OCXO to close the difference.   The resolution would be
>>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 second
>>> period it might wrk well enough.  I can't know without doing a more detailed
>>> design
>>
>> Do some of the counter/timer modules have an option to run the counter off an
>> internal clock and copy the value into another register on an external 
>> signal?
>>
>> That avoids any interrupt latency.
>>
>>
>>
>>
>> --
>> These are my opinions.  I hate spam.
>>
>>
>>
>>
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

That would be an input capture rather than an interrupt.

Bob

On Dec 6, 2012, at 6:16 PM, Hal Murray  wrote:

> 
> albertson.ch...@gmail.com said:
>> You'd have to seriously divide down the output from the 10MHz OCXO if you
>> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
>> at the higher clock rate you'd still have poor resolution.
> 
>> I image each interrupt handler would sample some internal counter and the
>> background task would look at the delta between the two and adjust the DAC
>> to drive the OCXO to close the difference.   The resolution would be
>> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 second
>> period it might wrk well enough.  I can't know without doing a more detailed
>> design 
> 
> Do some of the counter/timer modules have an option to run the counter off an 
> internal clock and copy the value into another register on an external signal?
> 
> That avoids any interrupt latency.
> 
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Hal Murray]

albertson.ch...@gmail.com said:
> You'd have to seriously divide down the output from the 10MHz OCXO if you
> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
> at the higher clock rate you'd still have poor resolution.

> I image each interrupt handler would sample some internal counter and the
> background task would look at the delta between the two and adjust the DAC
> to drive the OCXO to close the difference.   The resolution would be
> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000 second
> period it might wrk well enough.  I can't know without doing a more detailed
> design 

Do some of the counter/timer modules have an option to run the counter off an 
internal clock and copy the value into another register on an external signal?

That avoids any interrupt latency.




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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The math is pretty straightforward.

Let's say the clock is 10 MHz, that's 100 ns.

Say a handful is 5 +/- 3 (2 to 8) 

Your measure will bounce up and down by 6x100 ns = 600 ns.

Over a 100 second period that's going to be 6.0 x10^-9 bounce in the data. 

If you run a 100 second loop as well, that's the noise in the loop (just from 
one source).

Six times faster clock, you get 1.0x10^-9. Step up the "handful" for the faster 
clock's pipeline and you may be back at the same place.

Take a bunch of readings (you only get one a second) and average - things get 
better by square root of the samples. That's IF you have enough jitter / dither 
in the system to smooth things out. If you have "lumpy" noise (as is often the 
case with interrupts) you may get very little gain from averaging. 

With a 100 second loop, a TBolt is doing sub 1x10^-11, so you are at least 100X 
worse.

Bob

On Dec 6, 2012, at 5:57 PM, Chris Albertson  wrote:

> You'd have to seriously divide down the output from the 10MHz OCXO if you
> were going to use it as an interrupt.  Maybe to divide by 10,000? and even
> at the higher clock rate you'd still have poor resolution.
> 
> I image each interrupt handler would sample some internal counter and the
> background task would look at the delta between the two and adjust the DAC
> to drive the OCXO to close the difference.   The resolution would be
> (maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
> second period it might wrk well enough.  I can't know without doing a more
> detailed design
> 
> 
> On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:
> 
>> Chris:
>> 
>>> The question I have again is about a simple phase detector.
>> 
>> I did ask if the arduino interrupt ports could be used as a phase
>> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
>> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
>> work? I'm simply too new at this to decide.
>> 
>> Don
>> 
>> --
>> "Neither the voice of authority nor the weight of reason and argument
>> are as significant as experiment, for thence comes quiet to the mind."
>> De Erroribus Medicorum, R. Bacon, 13th century.
>> "If you don't know what it is, don't poke it."
>> Ghost in the Shell
>> 
>> 
>> Dr. Don Latham AJ7LL
>> Six Mile Systems LLP
>> 17850 Six Mile Road
>> POB 134
>> Huson, MT, 59846
>> VOX 406-626-4304
>> www.lightningforensics.com
>> www.sixmilesystems.com
>> 
>> 
>> 
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>> and follow the instructions there.
>> 
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

You'd have to seriously divide down the output from the 10MHz OCXO if you
were going to use it as an interrupt.  Maybe to divide by 10,000? and even
at the higher clock rate you'd still have poor resolution.

I image each interrupt handler would sample some internal counter and the
background task would look at the delta between the two and adjust the DAC
to drive the OCXO to close the difference.   The resolution would be
(maybe?) a "handful" of clock cycles.   Given enough time, say a 1000
second period it might wrk well enough.  I can't know without doing a more
detailed design


On Thu, Dec 6, 2012 at 1:59 AM, Don Latham  wrote:

> Chris:
>
> > The question I have again is about a simple phase detector.
>
> I did ask if the arduino interrupt ports could be used as a phase
> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
> work? I'm simply too new at this to decide.
>
> Don
>
> --
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.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.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[John Ackermann N8UR]

On 12/6/2012 4:35 PM, Charles P. Steinmetz wrote:


 From my perspective, the most interesting development would be an offer
by someone with a very well equipped lab to test any DIY GPSDO with a
consistent protocol and publish the results.  That way, we could all see
how the various approaches compare with respect to the characteristics
that are most important to each of us.


This is interesting, and I could bite -- for a limited definition of 
"very well equipped."


What's *really* interesting, though, is the idea that collectively we 
might develop some standard measurement protocols that would be 
reproducible in a number of (amateur) labs.


John


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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The single best thing about a TBolt is Lady Heather.

Consider how many years it's taken to get it to where it is today. Consider
how many people have worked extensively on it. It's a wonderful thing to
have available. 

Could you make a homebrew gizmo look "just like a TBolt"? Sure you could. It
might well take you forever to do all the reverse engineering, validation,
and testing, but it can be done. I'd guess it would take less time to
re-write a version of LH from scratch

--

Another thing to consider:

Z3801's got scrapped out, flooded the market, and the price went to "real
good". The supply dried up and prices climbed. This took years.

TBolts went through the same cycle. Again over a time period of many years.

In both cases you had a long time to look at them and make a decision about
weather you wanted one or not. It was never a "buy it this week or they are
gone" thing. 

These aren't the only things that will ever get scrapped. There's something
somewhere in the world that's going to get junked. Some sort of GPSDO will
flood the market in the future. It will be around for many years at low
prices. 

What ever you do as a project needs to be pretty good to survive the
competition. Otherwise it'll die before anybody ever sees one. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Charles P. Steinmetz
Sent: Thursday, December 06, 2012 4:36 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Don wrote:

>you guys are reinforcing that just because its' cheap won't mean it 
>won't work.

Of course it doesn't.  But keep in mind that "working" spans several 
orders of magnitude in this area, and what one needs to design and 
build depends on what degree of "working" one needs to support the 
uses to which the finished standard will be put.  First, there is 
performance during normal operation (good, continuous satellite 
tracking) -- ADEV at all taus of interest, PN at all offsets of 
interest, distortion and spurs, residual AM, stability over 
temperature, PPS jitter, etc.  Then, there is performance with poor 
satellite visibility, and finally performance in holdover (no 
satellite visibility) for however long one needs it (if one needs it 
at all, which many amateurs may not).  For some, there will be power 
consumption issues.  There may also be issues of interfacing to 
monitoring devices, both simple (e.g., LCD status displays) and 
sophisticated (e.g., computer running Lady Heather or Z38xx).  Does 
it need to work with existing programs, or is writing a new 
monitoring program part of the project?  Then there are the 
construction issues.  Does it need to be assembled entirely from 
connectorized modules, no soldering required?  Or capable of being 
thrown together on a scrap of perfboard?  Or will a PC card be 
designed?  If so, can it use SMT parts?  How adaptable must it be, 
particularly in accommodating different oscillators?  Does it need to 
support rubidium oscillators as well as quartz?  Etc., etc., etc.

Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively 
affordable, so they are natural benchmarks for any DIY project.

 From my perspective, the most interesting development would be an 
offer by someone with a very well equipped lab to test any DIY GPSDO 
with a consistent protocol and publish the results.  That way, we 
could all see how the various approaches compare with respect to the 
characteristics that are most important to each of us.

Best regards,

Charles







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Re: [time-nuts] GPSDO Alternatives

[Charles P. Steinmetz]

Don wrote:

you guys are reinforcing that just because its' cheap won't mean it 
won't work.


Of course it doesn't.  But keep in mind that "working" spans several 
orders of magnitude in this area, and what one needs to design and 
build depends on what degree of "working" one needs to support the 
uses to which the finished standard will be put.  First, there is 
performance during normal operation (good, continuous satellite 
tracking) -- ADEV at all taus of interest, PN at all offsets of 
interest, distortion and spurs, residual AM, stability over 
temperature, PPS jitter, etc.  Then, there is performance with poor 
satellite visibility, and finally performance in holdover (no 
satellite visibility) for however long one needs it (if one needs it 
at all, which many amateurs may not).  For some, there will be power 
consumption issues.  There may also be issues of interfacing to 
monitoring devices, both simple (e.g., LCD status displays) and 
sophisticated (e.g., computer running Lady Heather or Z38xx).  Does 
it need to work with existing programs, or is writing a new 
monitoring program part of the project?  Then there are the 
construction issues.  Does it need to be assembled entirely from 
connectorized modules, no soldering required?  Or capable of being 
thrown together on a scrap of perfboard?  Or will a PC card be 
designed?  If so, can it use SMT parts?  How adaptable must it be, 
particularly in accommodating different oscillators?  Does it need to 
support rubidium oscillators as well as quartz?  Etc., etc., etc.


Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively 
affordable, so they are natural benchmarks for any DIY project.


From my perspective, the most interesting development would be an 
offer by someone with a very well equipped lab to test any DIY GPSDO 
with a consistent protocol and publish the results.  That way, we 
could all see how the various approaches compare with respect to the 
characteristics that are most important to each of us.


Best regards,

Charles







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Re: [time-nuts] GPSDO Alternatives

[dlewis6767]

I'm excited, for sure.

I've got a whole box of goodies over here I bought full of the Arduino uP 
and a ton of its 'shields'.  Been collecting, so-to-speak.


I just new I could use it for a, down-and-dirty GPSDO.  The Trimble Lassen 
looks good down to 20ns UTC (I got two for $10); then add a cheap datum 
ocxo; coupled that with the Arduino.  Voilà.


I can't wait, ..and you guys are reinforcing that just because its' cheap 
won't mean it won't work.


-Don






--
From: 
Sent: Thursday, December 06, 2012 1:38 PM
To: 
Subject: Re: [time-nuts] GPSDO Alternatives


Paul
I agree. That is my main frustration, lot of talk no results. The good 
part

of time nuts is that I have made some very good contacts that share my
interest  of actually building some things and results are great.
Remember the Loran simulator?

Bert Kehren


In a message dated 12/6/2012 1:17:14 P.M. Eastern Standard Time,
paulsw...@gmail.com writes:

Boy do I  have to agree. uProcs by the dozens and with all kinds of
counters
onboard.
I think it was Bob who said none of thats the  challenge.
It is the phase comparison method and a stable D/A converter and 
reference.

From what I have seen and I could be dead wrong here the on  board uprocs
have D/As but the quality is simply OK.
The other comment  is that whoever writes the software gets to choose the
software and  everything else. Its actually not really democratic at all.
Cause we will  all use it if its reasonably good. ;-)
If I do it it will be basic! Though  it will run at very high speeds. Now
someone should be jumping in with  Forth real soon now.
Last tidbit the Rasberry is a pretty interesting  widget and there had 
been

a thread about a time server. Was looking forward  to the results. Nothing
ever  happened.
Regards
Paul
WB8TSL

On Thu, Dec 6, 2012 at 1:00 PM,  Bob Camp  wrote:


Hi

It's a  rare microcontroller these days that does *not* come with a free
 tool
chain. Same goes for the debugger. Most MCU lines have family  members

with

similarly low (or lower) prices and good availability.  They pretty much

all

either work with a crystal two caps and a  resistor. Most will run fine

with

none of the above on the internal  clock.

Bob

-Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]  On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06,  2012 12:45 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts]  GPSDO Alternatives

Arduino is Dirt Cheap!
At it's  cheapest it is just an atmel AVR, a crystal, 2 caps and a

resistor

 with the arduino bootloader programmed into it. Easily obtainable from
 several sources for 5 bucks or so. All the code, toolchain etc. (the
 ecosystem as it were) is free. it's real easy to put one together on a
 piece

of perfboard. If you're gonna put the phase detector,  dividers etc.
together

anyway there's really no need  to clutter things up with some ginormous
commercial arduino  board.
Dale

-Original Message-
From:  Keenan Tims
Sent: Thursday, December 06, 2012 10:38 AM
To:  time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO  Alternatives

As a lurker, I just want to chime in and say that  I for one would love
to see an open-source GPSDO implementation. There  are quite a few open
hardware designs out there, but as Bob suggests,  all the interesting
bits are tied up in the closed-source software  they run. And most of
them are no longer maintained, meaning it's  getting hard to find parts.

I've thought on designing a  hardware platform to support a GPSDO as
well, but don't have the  time-nut or control theory skills (or
equipment) necessary to make the  software any good. My hope at the time
was that a build it and they  will come approach would solve those
problems, but I haven't had time  to make that gamble.

As far as uP choice, Arduino's only  saving grace is the pool of existing
'developers' in the amateur  community for it - but that's perhaps a big
deal here. It's expensive,  doesn't include debug hardware, and is slow
with not many peripherals.  I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you  want to stay cheap and slow.

Keenan
 VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:
 > On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
 >>
>> If there is one thing I learned, it is that one is  never finished
>> improving
>>  the software.  That is why we are time-nuts I guess.
>>
> This is  the reason I suggested using the Arduino.  It is so easy to
>  program
> that MANY people will be able to contribute.  That  is my goal, a GPSDO
> that
> can be a "living project"  that is not dependent on one or a few

experts.

> I'd like to see a  budget of well under $100, again so that more people
can
>  contribute and experiment.
>

Re: [time-nuts] GPSDO Alternatives

[EWKehren]

Paul
I agree. That is my main frustration, lot of talk no results. The good part 
 of time nuts is that I have made some very good contacts that share my 
interest  of actually building some things and results are great.
Remember the Loran simulator?
 
Bert Kehren
 
 
In a message dated 12/6/2012 1:17:14 P.M. Eastern Standard Time,  
paulsw...@gmail.com writes:

Boy do I  have to agree. uProcs by the dozens and with all kinds of  
counters
onboard.
I think it was Bob who said none of thats the  challenge.
It is the phase comparison method and a stable D/A converter and  reference.
>From what I have seen and I could be dead wrong here the on  board uprocs
have D/As but the quality is simply OK.
The other comment  is that whoever writes the software gets to choose the
software and  everything else. Its actually not really democratic at all.
Cause we will  all use it if its reasonably good. ;-)
If I do it it will be basic! Though  it will run at very high speeds. Now
someone should be jumping in with  Forth real soon now.
Last tidbit the Rasberry is a pretty interesting  widget and there had been
a thread about a time server. Was looking forward  to the results. Nothing
ever  happened.
Regards
Paul
WB8TSL

On Thu, Dec 6, 2012 at 1:00 PM,  Bob Camp  wrote:

> Hi
>
> It's a  rare microcontroller these days that does *not* come with a free
>  tool
> chain. Same goes for the debugger. Most MCU lines have family  members 
with
> similarly low (or lower) prices and good availability.  They pretty much 
all
> either work with a crystal two caps and a  resistor. Most will run fine 
with
> none of the above on the internal  clock.
>
> Bob
>
> -Original Message-
>  From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]  On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06,  2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts]  GPSDO Alternatives
>
> Arduino is Dirt Cheap!
> At it's  cheapest it is just an atmel AVR, a crystal, 2 caps and a 
resistor
>  with the arduino bootloader programmed into it. Easily obtainable from
>  several sources for 5 bucks or so. All the code, toolchain etc. (the
>  ecosystem as it were) is free. it's real easy to put one together on a
>  piece
>
> of perfboard. If you're gonna put the phase detector,  dividers etc.
> together
>
> anyway there's really no need  to clutter things up with some ginormous
> commercial arduino  board.
> Dale
>
> -----Original Message-----
> From:  Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To:  time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO  Alternatives
>
> As a lurker, I just want to chime in and say that  I for one would love
> to see an open-source GPSDO implementation. There  are quite a few open
> hardware designs out there, but as Bob suggests,  all the interesting
> bits are tied up in the closed-source software  they run. And most of
> them are no longer maintained, meaning it's  getting hard to find parts.
>
> I've thought on designing a  hardware platform to support a GPSDO as
> well, but don't have the  time-nut or control theory skills (or
> equipment) necessary to make the  software any good. My hope at the time
> was that a build it and they  will come approach would solve those
> problems, but I haven't had time  to make that gamble.
>
> As far as uP choice, Arduino's only  saving grace is the pool of existing
> 'developers' in the amateur  community for it - but that's perhaps a big
> deal here. It's expensive,  doesn't include debug hardware, and is slow
> with not many peripherals.  I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you  want to stay cheap and slow.
>
> Keenan
>  VE7XEN
>
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
>  > On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>  >>
> >> If there is one thing I learned, it is that one is  never finished
> >> improving
> >>  the software.  That is why we are time-nuts I guess.
> >>
> > This is  the reason I suggested using the Arduino.  It is so easy to
> >  program
> > that MANY people will be able to contribute.  That  is my goal, a GPSDO
> > that
> > can be a "living project"  that is not dependent on one or a few 
experts.
> > I'd like to see a  budget of well under $100, again so that more people
> can
> >  contribute and experiment.
> >
> > A design that can evolve  will have just about any performance people
> want.
> >   So don't worry about if it is 1E-12 or 1E-15.  Just make it  
transparent
> > and easy to understand and modify.
>  >
>
>
>  __

Re: [time-nuts] GPSDO Alternatives

[EWKehren]

How about quit talking and build something and show us some results!
Bert Kehren
 
 
In a message dated 12/6/2012 2:09:38 P.M. Eastern Standard Time,  
d...@nap-us.com writes:

Bob,
Did Atmel (AVR) kill your dog or something?
They have  some pretty powerful MCU's. Are you flatly stating that none of 
them could  be used for a "very nice GPSDO"?
Dale
Just fooling around, no offence  intended.


-Original Message- 
From: Bob Camp
Sent:  Thursday, December 06, 2012 1:57 PM
To: 'Discussion of precise time and  frequency measurement'
Subject: Re: [time-nuts] GPSDO  Alternatives

Hi

That is where most of these tools were many  years ago. Competition has
forced them to open things up quite a bit. You  can code a very nice GPSDO
and not use anything but freely available tools.  You can do it on several
processors, none of which come from AVR (and thus  use the Arduino chain).

Bob

-Original Message-
From:  time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of  Dale J. Robertson
Sent: Thursday, December 06, 2012 1:47 PM
To:  Discussion of precise time and frequency measurement
Cc: Discussion of  precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO  Alternatives

Most of the "free" tool chains are not truly free I.e.  open source 
including
all libraries and coupled with an open source  compiler and debugger. In
addition few of them are currently offered in  hobbyist friendly DIP
packages.
Once you resign yourself to having to  build hardware glue for some of the
special functions required, CPU  performance becomes mostly a non issue. For
quick and dirty lash ups on  perf board (as I believe the OP is looking 
for),
It's hard to beat a pic or  Avr and for code re-use from a large online
community it's hard to beat the  arduino eek-o-system
Dale
Sent from my iPhone

On Dec 6, 2012, at  1:00 PM, "Bob Camp"  wrote:

>  Hi
>
> It's a rare microcontroller these days that does *not* come  with a free
tool
> chain. Same goes for the debugger. Most MCU lines  have family members 
with
> similarly low (or lower) prices and good  availability. They pretty much
all
> either work with a crystal two  caps and a resistor. Most will run fine
with
> none of the above on  the internal clock.
>
> Bob
>
> -Original  Message-
> From: time-nuts-boun...@febo.com  [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J.  Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To:  time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO  Alternatives
>
> Arduino is Dirt Cheap!
> At it's cheapest  it is just an atmel AVR, a crystal, 2 caps and a 
resistor

> with the  arduino bootloader programmed into it. Easily obtainable from
> several  sources for 5 bucks or so. All the code, toolchain etc. (the
> ecosystem  as it were) is free. it's real easy to put one together on  a
piece
>
> of perfboard. If you're gonna put the phase  detector, dividers etc.
together
>
> anyway there's really no  need to clutter things up with some ginormous
> commercial arduino  board.
> Dale
>
> -Original Message- 
> From:  Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To:  time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO  Alternatives
>
> As a lurker, I just want to chime in and say that  I for one would love
> to see an open-source GPSDO implementation. There  are quite a few open
> hardware designs out there, but as Bob suggests,  all the interesting
> bits are tied up in the closed-source software  they run. And most of
> them are no longer maintained, meaning it's  getting hard to find parts.
>
> I've thought on designing a  hardware platform to support a GPSDO as
> well, but don't have the  time-nut or control theory skills (or
> equipment) necessary to make the  software any good. My hope at the time
> was that a build it and they  will come approach would solve those
> problems, but I haven't had time  to make that gamble.
>
> As far as uP choice, Arduino's only  saving grace is the pool of existing
> 'developers' in the amateur  community for it - but that's perhaps a big
> deal here. It's expensive,  doesn't include debug hardware, and is slow
> with not many peripherals.  I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you  want to stay cheap and slow.
>
> Keenan
>  VE7XEN
>
> On 2012-12-06 1:28 AM, Chris Albertson  wrote:
>> On Wed, Dec 5, 2012 at 2:50 PM,   wrote:
>>>
>>> If there is one thing I learned, it is  that one is never finished
>>> improving
>>> the  software. That is why we are time-nuts I guess.
>> This is the reason  I suggested using the Arduino.  It is so easy to
>>  program
>

Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

By no means am I saying that they *can't* be used. My point is that there
are a multitude of alternatives that are at least equally as cheap and
attractive. There is no clear "you must use this one" to pick. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 2:09 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] GPSDO Alternatives

Bob,
Did Atmel (AVR) kill your dog or something?
They have some pretty powerful MCU's. Are you flatly stating that none of 
them could be used for a "very nice GPSDO"?
Dale
Just fooling around, no offence intended.


-Original Message- 
From: Bob Camp
Sent: Thursday, December 06, 2012 1:57 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] GPSDO Alternatives

Hi

That is where most of these tools were many years ago. Competition has
forced them to open things up quite a bit. You can code a very nice GPSDO
and not use anything but freely available tools. You can do it on several
processors, none of which come from AVR (and thus use the Arduino chain).

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 1:47 PM
To: Discussion of precise time and frequency measurement
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Most of the "free" tool chains are not truly free I.e. open source including
all libraries and coupled with an open source compiler and debugger. In
addition few of them are currently offered in hobbyist friendly DIP
packages.
Once you resign yourself to having to build hardware glue for some of the
special functions required, CPU performance becomes mostly a non issue. For
quick and dirty lash ups on perf board (as I believe the OP is looking for),
It's hard to beat a pic or Avr and for code re-use from a large online
community it's hard to beat the arduino eek-o-system
Dale
Sent from my iPhone

On Dec 6, 2012, at 1:00 PM, "Bob Camp"  wrote:

> Hi
>
> It's a rare microcontroller these days that does *not* come with a free
tool
> chain. Same goes for the debugger. Most MCU lines have family members with
> similarly low (or lower) prices and good availability. They pretty much
all
> either work with a crystal two caps and a resistor. Most will run fine
with
> none of the above on the internal clock.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> Arduino is Dirt Cheap!
> At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor

> with the arduino bootloader programmed into it. Easily obtainable from
> several sources for 5 bucks or so. All the code, toolchain etc. (the
> ecosystem as it were) is free. it's real easy to put one together on a
piece
>
> of perfboard. If you're gonna put the phase detector, dividers etc.
together
>
> anyway there's really no need to clutter things up with some ginormous
> commercial arduino board.
> Dale
>
> -Original Message- 
> From: Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> As a lurker, I just want to chime in and say that I for one would love
> to see an open-source GPSDO implementation. There are quite a few open
> hardware designs out there, but as Bob suggests, all the interesting
> bits are tied up in the closed-source software they run. And most of
> them are no longer maintained, meaning it's getting hard to find parts.
>
> I've thought on designing a hardware platform to support a GPSDO as
> well, but don't have the time-nut or control theory skills (or
> equipment) necessary to make the software any good. My hope at the time
> was that a build it and they will come approach would solve those
> problems, but I haven't had time to make that gamble.
>
> As far as uP choice, Arduino's only saving grace is the pool of existing
> 'developers' in the amateur community for it - but that's perhaps a big
> deal here. It's expensive, doesn't include debug hardware, and is slow
> with not many peripherals. I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you want to stay cheap and slow.
>
> Keenan
> VE7XEN
>
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
>> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>

Re: [time-nuts] GPSDO Alternatives

[Dale J. Robertson]

Bob,
Did Atmel (AVR) kill your dog or something?
They have some pretty powerful MCU's. Are you flatly stating that none of 
them could be used for a "very nice GPSDO"?

Dale
Just fooling around, no offence intended.


-Original Message- 
From: Bob Camp

Sent: Thursday, December 06, 2012 1:57 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] GPSDO Alternatives

Hi

That is where most of these tools were many years ago. Competition has
forced them to open things up quite a bit. You can code a very nice GPSDO
and not use anything but freely available tools. You can do it on several
processors, none of which come from AVR (and thus use the Arduino chain).

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 1:47 PM
To: Discussion of precise time and frequency measurement
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Most of the "free" tool chains are not truly free I.e. open source including
all libraries and coupled with an open source compiler and debugger. In
addition few of them are currently offered in hobbyist friendly DIP
packages.
Once you resign yourself to having to build hardware glue for some of the
special functions required, CPU performance becomes mostly a non issue. For
quick and dirty lash ups on perf board (as I believe the OP is looking for),
It's hard to beat a pic or Avr and for code re-use from a large online
community it's hard to beat the arduino eek-o-system
Dale
Sent from my iPhone

On Dec 6, 2012, at 1:00 PM, "Bob Camp"  wrote:


Hi

It's a rare microcontroller these days that does *not* come with a free

tool

chain. Same goes for the debugger. Most MCU lines have family members with
similarly low (or lower) prices and good availability. They pretty much

all

either work with a crystal two caps and a resistor. Most will run fine

with

none of the above on the internal clock.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 12:45 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

Arduino is Dirt Cheap!
At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor



with the arduino bootloader programmed into it. Easily obtainable from
several sources for 5 bucks or so. All the code, toolchain etc. (the
ecosystem as it were) is free. it's real easy to put one together on a

piece


of perfboard. If you're gonna put the phase detector, dividers etc.

together


anyway there's really no need to clutter things up with some ginormous
commercial arduino board.
Dale

-Original Message- 
From: Keenan Tims

Sent: Thursday, December 06, 2012 10:38 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer maintained, meaning it's getting hard to find parts.

I've thought on designing a hardware platform to support a GPSDO as
well, but don't have the time-nut or control theory skills (or
equipment) necessary to make the software any good. My hope at the time
was that a build it and they will come approach would solve those
problems, but I haven't had time to make that gamble.

As far as uP choice, Arduino's only saving grace is the pool of existing
'developers' in the amateur community for it - but that's perhaps a big
deal here. It's expensive, doesn't include debug hardware, and is slow
with not many peripherals. I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you want to stay cheap and slow.

Keenan
VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:

On Wed, Dec 5, 2012 at 2:50 PM,  wrote:


If there is one thing I learned, it is that one is never finished
improving
the software. That is why we are time-nuts I guess.

This is the reason I suggested using the Arduino.  It is so easy to
program
that MANY people will be able to contribute.  That is my goal, a GPSDO
that
can be a "living project" that is not dependent on one or a few experts.
I'd like to see a budget of well under $100, again so that more people

can

contribute and experiment.

A design that can evolve will have just about any performance people

want.

So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
and easy to understand and modify.



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htt

Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

That is where most of these tools were many years ago. Competition has
forced them to open things up quite a bit. You can code a very nice GPSDO
and not use anything but freely available tools. You can do it on several
processors, none of which come from AVR (and thus use the Arduino chain).

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 1:47 PM
To: Discussion of precise time and frequency measurement
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Most of the "free" tool chains are not truly free I.e. open source including
all libraries and coupled with an open source compiler and debugger. In
addition few of them are currently offered in hobbyist friendly DIP
packages.
Once you resign yourself to having to build hardware glue for some of the
special functions required, CPU performance becomes mostly a non issue. For
quick and dirty lash ups on perf board (as I believe the OP is looking for),
It's hard to beat a pic or Avr and for code re-use from a large online
community it's hard to beat the arduino eek-o-system
Dale
Sent from my iPhone

On Dec 6, 2012, at 1:00 PM, "Bob Camp"  wrote:

> Hi
> 
> It's a rare microcontroller these days that does *not* come with a free
tool
> chain. Same goes for the debugger. Most MCU lines have family members with
> similarly low (or lower) prices and good availability. They pretty much
all
> either work with a crystal two caps and a resistor. Most will run fine
with
> none of the above on the internal clock.
> 
> Bob 
> 
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
> 
> Arduino is Dirt Cheap!
> At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor

> with the arduino bootloader programmed into it. Easily obtainable from 
> several sources for 5 bucks or so. All the code, toolchain etc. (the 
> ecosystem as it were) is free. it's real easy to put one together on a
piece
> 
> of perfboard. If you're gonna put the phase detector, dividers etc.
together
> 
> anyway there's really no need to clutter things up with some ginormous 
> commercial arduino board.
> Dale
> 
> -Original Message- 
> From: Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
> 
> As a lurker, I just want to chime in and say that I for one would love
> to see an open-source GPSDO implementation. There are quite a few open
> hardware designs out there, but as Bob suggests, all the interesting
> bits are tied up in the closed-source software they run. And most of
> them are no longer maintained, meaning it's getting hard to find parts.
> 
> I've thought on designing a hardware platform to support a GPSDO as
> well, but don't have the time-nut or control theory skills (or
> equipment) necessary to make the software any good. My hope at the time
> was that a build it and they will come approach would solve those
> problems, but I haven't had time to make that gamble.
> 
> As far as uP choice, Arduino's only saving grace is the pool of existing
> 'developers' in the amateur community for it - but that's perhaps a big
> deal here. It's expensive, doesn't include debug hardware, and is slow
> with not many peripherals. I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you want to stay cheap and slow.
> 
> Keenan
> VE7XEN
> 
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
>> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>> 
>>> If there is one thing I learned, it is that one is never finished 
>>> improving
>>> the software. That is why we are time-nuts I guess.
>> This is the reason I suggested using the Arduino.  It is so easy to 
>> program
>> that MANY people will be able to contribute.  That is my goal, a GPSDO 
>> that
>> can be a "living project" that is not dependent on one or a few experts.
>> I'd like to see a budget of well under $100, again so that more people
can
>> contribute and experiment.
>> 
>> A design that can evolve will have just about any performance people
want.
>> So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
>> and easy to understand and modify.
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsub

Re: [time-nuts] GPSDO Alternatives

[Dale J. Robertson]

Most of the "free" tool chains are not truly free I.e. open source including 
all libraries and coupled with an open source compiler and debugger. In 
addition few of them are currently offered in hobbyist friendly DIP packages.
Once you resign yourself to having to build hardware glue for some of the 
special functions required, CPU performance becomes mostly a non issue. For 
quick and dirty lash ups on perf board (as I believe the OP is looking for),
It's hard to beat a pic or Avr and for code re-use from a large online 
community it's hard to beat the arduino eek-o-system
Dale
Sent from my iPhone

On Dec 6, 2012, at 1:00 PM, "Bob Camp"  wrote:

> Hi
> 
> It's a rare microcontroller these days that does *not* come with a free tool
> chain. Same goes for the debugger. Most MCU lines have family members with
> similarly low (or lower) prices and good availability. They pretty much all
> either work with a crystal two caps and a resistor. Most will run fine with
> none of the above on the internal clock.
> 
> Bob 
> 
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
> 
> Arduino is Dirt Cheap!
> At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor 
> with the arduino bootloader programmed into it. Easily obtainable from 
> several sources for 5 bucks or so. All the code, toolchain etc. (the 
> ecosystem as it were) is free. it's real easy to put one together on a piece
> 
> of perfboard. If you're gonna put the phase detector, dividers etc. together
> 
> anyway there's really no need to clutter things up with some ginormous 
> commercial arduino board.
> Dale
> 
> -Original Message- 
> From: Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
> 
> As a lurker, I just want to chime in and say that I for one would love
> to see an open-source GPSDO implementation. There are quite a few open
> hardware designs out there, but as Bob suggests, all the interesting
> bits are tied up in the closed-source software they run. And most of
> them are no longer maintained, meaning it's getting hard to find parts.
> 
> I've thought on designing a hardware platform to support a GPSDO as
> well, but don't have the time-nut or control theory skills (or
> equipment) necessary to make the software any good. My hope at the time
> was that a build it and they will come approach would solve those
> problems, but I haven't had time to make that gamble.
> 
> As far as uP choice, Arduino's only saving grace is the pool of existing
> 'developers' in the amateur community for it - but that's perhaps a big
> deal here. It's expensive, doesn't include debug hardware, and is slow
> with not many peripherals. I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you want to stay cheap and slow.
> 
> Keenan
> VE7XEN
> 
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
>> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>> 
>>> If there is one thing I learned, it is that one is never finished 
>>> improving
>>> the software. That is why we are time-nuts I guess.
>> This is the reason I suggested using the Arduino.  It is so easy to 
>> program
>> that MANY people will be able to contribute.  That is my goal, a GPSDO 
>> that
>> can be a "living project" that is not dependent on one or a few experts.
>> I'd like to see a budget of well under $100, again so that more people can
>> contribute and experiment.
>> 
>> A design that can evolve will have just about any performance people want.
>> So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
>> and easy to understand and modify.
> 
> 
> ___
> 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. 
> 
> 
> ___
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> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 
> 
> 
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/6/12 9:45 AM, Dale J. Robertson wrote:

Arduino is Dirt Cheap!


And available over the counter retail at hundreds of Radio Shacks..
You get an idea during the day, and you can run out and buy one right 
then.. (yes, you can mail order, but the fastest turnaround is a few 
days, unless you pay an enormous "next day shipping" premium)


This is one reason why Arduino is by far and away the most common uProc 
in, e.g., high school science projects.



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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

This is a project that is a multi year endeavor in a commercial setting.
That's where you have multiple people on the payroll who can put 40+ hours a
week into it. You are set up with groups of people who do this or that. They
all aren't on this job full time, but there's a lot of resources available.

As a hobby project, it's going to take longer. Signing up for years of work,
and sticking to it is not at all easy. Getting to make the "fun decisions"
is about the only compensation for doing an awful lot of work. Unless you
just won the lottery, there's also a non-trivial cost to making up several
revisions of boards. 

Not at all simple. Not un-doable either. 

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of paul swed
Sent: Thursday, December 06, 2012 1:17 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Boy do I have to agree. uProcs by the dozens and with all kinds of counters
onboard.
I think it was Bob who said none of thats the challenge.
It is the phase comparison method and a stable D/A converter and reference.
>From what I have seen and I could be dead wrong here the on board uprocs
have D/As but the quality is simply OK.
The other comment is that whoever writes the software gets to choose the
software and everything else. Its actually not really democratic at all.
Cause we will all use it if its reasonably good. ;-)
If I do it it will be basic! Though it will run at very high speeds. Now
someone should be jumping in with Forth real soon now.
Last tidbit the Rasberry is a pretty interesting widget and there had been
a thread about a time server. Was looking forward to the results. Nothing
ever happened.
Regards
Paul
WB8TSL

On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp  wrote:

> Hi
>
> It's a rare microcontroller these days that does *not* come with a free
> tool
> chain. Same goes for the debugger. Most MCU lines have family members with
> similarly low (or lower) prices and good availability. They pretty much
all
> either work with a crystal two caps and a resistor. Most will run fine
with
> none of the above on the internal clock.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> Arduino is Dirt Cheap!
> At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor
> with the arduino bootloader programmed into it. Easily obtainable from
> several sources for 5 bucks or so. All the code, toolchain etc. (the
> ecosystem as it were) is free. it's real easy to put one together on a
> piece
>
> of perfboard. If you're gonna put the phase detector, dividers etc.
> together
>
> anyway there's really no need to clutter things up with some ginormous
> commercial arduino board.
> Dale
>
> -Original Message-
> From: Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> As a lurker, I just want to chime in and say that I for one would love
> to see an open-source GPSDO implementation. There are quite a few open
> hardware designs out there, but as Bob suggests, all the interesting
> bits are tied up in the closed-source software they run. And most of
> them are no longer maintained, meaning it's getting hard to find parts.
>
> I've thought on designing a hardware platform to support a GPSDO as
> well, but don't have the time-nut or control theory skills (or
> equipment) necessary to make the software any good. My hope at the time
> was that a build it and they will come approach would solve those
> problems, but I haven't had time to make that gamble.
>
> As far as uP choice, Arduino's only saving grace is the pool of existing
> 'developers' in the amateur community for it - but that's perhaps a big
> deal here. It's expensive, doesn't include debug hardware, and is slow
> with not many peripherals. I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you want to stay cheap and slow.
>
> Keenan
> VE7XEN
>
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
> > On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
> >>
> >> If there is one thing I learned, it is that one is never finished
> >> improving
> >>  the software. That is why we are time-nuts I guess.
> >>
> > This is the reason I suggested using the Arduino.  It is so easy to
> > program
> > that MANY people will be able to contribute.  That is my goal, a GPSDO

Re: [time-nuts] GPSDO Alternatives

[paul swed]

Boy do I have to agree. uProcs by the dozens and with all kinds of counters
onboard.
I think it was Bob who said none of thats the challenge.
It is the phase comparison method and a stable D/A converter and reference.
>From what I have seen and I could be dead wrong here the on board uprocs
have D/As but the quality is simply OK.
The other comment is that whoever writes the software gets to choose the
software and everything else. Its actually not really democratic at all.
Cause we will all use it if its reasonably good. ;-)
If I do it it will be basic! Though it will run at very high speeds. Now
someone should be jumping in with Forth real soon now.
Last tidbit the Rasberry is a pretty interesting widget and there had been
a thread about a time server. Was looking forward to the results. Nothing
ever happened.
Regards
Paul
WB8TSL

On Thu, Dec 6, 2012 at 1:00 PM, Bob Camp  wrote:

> Hi
>
> It's a rare microcontroller these days that does *not* come with a free
> tool
> chain. Same goes for the debugger. Most MCU lines have family members with
> similarly low (or lower) prices and good availability. They pretty much all
> either work with a crystal two caps and a resistor. Most will run fine with
> none of the above on the internal clock.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Dale J. Robertson
> Sent: Thursday, December 06, 2012 12:45 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> Arduino is Dirt Cheap!
> At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor
> with the arduino bootloader programmed into it. Easily obtainable from
> several sources for 5 bucks or so. All the code, toolchain etc. (the
> ecosystem as it were) is free. it's real easy to put one together on a
> piece
>
> of perfboard. If you're gonna put the phase detector, dividers etc.
> together
>
> anyway there's really no need to clutter things up with some ginormous
> commercial arduino board.
> Dale
>
> -----Original Message-----
> From: Keenan Tims
> Sent: Thursday, December 06, 2012 10:38 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> As a lurker, I just want to chime in and say that I for one would love
> to see an open-source GPSDO implementation. There are quite a few open
> hardware designs out there, but as Bob suggests, all the interesting
> bits are tied up in the closed-source software they run. And most of
> them are no longer maintained, meaning it's getting hard to find parts.
>
> I've thought on designing a hardware platform to support a GPSDO as
> well, but don't have the time-nut or control theory skills (or
> equipment) necessary to make the software any good. My hope at the time
> was that a build it and they will come approach would solve those
> problems, but I haven't had time to make that gamble.
>
> As far as uP choice, Arduino's only saving grace is the pool of existing
> 'developers' in the amateur community for it - but that's perhaps a big
> deal here. It's expensive, doesn't include debug hardware, and is slow
> with not many peripherals. I'd second the STM32 ARM Cortex platform, or
> suggest MSP430 if you want to stay cheap and slow.
>
> Keenan
> VE7XEN
>
> On 2012-12-06 1:28 AM, Chris Albertson wrote:
> > On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
> >>
> >> If there is one thing I learned, it is that one is never finished
> >> improving
> >>  the software. That is why we are time-nuts I guess.
> >>
> > This is the reason I suggested using the Arduino.  It is so easy to
> > program
> > that MANY people will be able to contribute.  That is my goal, a GPSDO
> > that
> > can be a "living project" that is not dependent on one or a few experts.
> > I'd like to see a budget of well under $100, again so that more people
> can
> > contribute and experiment.
> >
> > A design that can evolve will have just about any performance people
> want.
> >  So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
> > and easy to understand and modify.
> >
>
>
> ___
> 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.
>
>
> ___
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> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
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> To unsubscribe, go to
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

It's a rare microcontroller these days that does *not* come with a free tool
chain. Same goes for the debugger. Most MCU lines have family members with
similarly low (or lower) prices and good availability. They pretty much all
either work with a crystal two caps and a resistor. Most will run fine with
none of the above on the internal clock.

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dale J. Robertson
Sent: Thursday, December 06, 2012 12:45 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

Arduino is Dirt Cheap!
At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor 
with the arduino bootloader programmed into it. Easily obtainable from 
several sources for 5 bucks or so. All the code, toolchain etc. (the 
ecosystem as it were) is free. it's real easy to put one together on a piece

of perfboard. If you're gonna put the phase detector, dividers etc. together

anyway there's really no need to clutter things up with some ginormous 
commercial arduino board.
Dale

-Original Message- 
From: Keenan Tims
Sent: Thursday, December 06, 2012 10:38 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer maintained, meaning it's getting hard to find parts.

I've thought on designing a hardware platform to support a GPSDO as
well, but don't have the time-nut or control theory skills (or
equipment) necessary to make the software any good. My hope at the time
was that a build it and they will come approach would solve those
problems, but I haven't had time to make that gamble.

As far as uP choice, Arduino's only saving grace is the pool of existing
'developers' in the amateur community for it - but that's perhaps a big
deal here. It's expensive, doesn't include debug hardware, and is slow
with not many peripherals. I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you want to stay cheap and slow.

Keenan
VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:
> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>
>> If there is one thing I learned, it is that one is never finished 
>> improving
>>  the software. That is why we are time-nuts I guess.
>>
> This is the reason I suggested using the Arduino.  It is so easy to 
> program
> that MANY people will be able to contribute.  That is my goal, a GPSDO 
> that
> can be a "living project" that is not dependent on one or a few experts.
> I'd like to see a budget of well under $100, again so that more people can
> contribute and experiment.
>
> A design that can evolve will have just about any performance people want.
>  So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
> and easy to understand and modify.
>


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Re: [time-nuts] GPSDO Alternatives

[Dale J. Robertson]

Arduino is Dirt Cheap!
At it's cheapest it is just an atmel AVR, a crystal, 2 caps and a resistor 
with the arduino bootloader programmed into it. Easily obtainable from 
several sources for 5 bucks or so. All the code, toolchain etc. (the 
ecosystem as it were) is free. it's real easy to put one together on a piece 
of perfboard. If you're gonna put the phase detector, dividers etc. together 
anyway there's really no need to clutter things up with some ginormous 
commercial arduino board.

Dale

-Original Message- 
From: Keenan Tims

Sent: Thursday, December 06, 2012 10:38 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer maintained, meaning it's getting hard to find parts.

I've thought on designing a hardware platform to support a GPSDO as
well, but don't have the time-nut or control theory skills (or
equipment) necessary to make the software any good. My hope at the time
was that a build it and they will come approach would solve those
problems, but I haven't had time to make that gamble.

As far as uP choice, Arduino's only saving grace is the pool of existing
'developers' in the amateur community for it - but that's perhaps a big
deal here. It's expensive, doesn't include debug hardware, and is slow
with not many peripherals. I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you want to stay cheap and slow.

Keenan
VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:

On Wed, Dec 5, 2012 at 2:50 PM,  wrote:


If there is one thing I learned, it is that one is never finished 
improving

 the software. That is why we are time-nuts I guess.

This is the reason I suggested using the Arduino.  It is so easy to 
program
that MANY people will be able to contribute.  That is my goal, a GPSDO 
that

can be a "living project" that is not dependent on one or a few experts.
I'd like to see a budget of well under $100, again so that more people can
contribute and experiment.

A design that can evolve will have just about any performance people want.
 So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
and easy to understand and modify.




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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

There are at least 500 different processors out there that could / might
work in a GPSDO. I can think of 40 or more families of parts one could look
at from more than a dozen companies. That's just counting the majors, and
not getting into any of the smaller outfits. It's also not including any of
the stuff that's likely overkill for the job. 

If you head off into ARM land, there are a number of hobby oriented projects
out there. Raspberry PI is one, there are *many* others in the sub $50 price
range. One of many is the 

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FRDM-KL25Z

The board is somewhere from free (sit in a room for 2 hours) to $13 (buy it
from distribution). It's got a full blown debugger and it will interface
with Adruino shields. It also has free software and a free RTOS to go with
it. For those who like data logging, it's set up for a SD card. Price wise -
at least as cheap as any Arduino I've seen. (... and it's a dual CPU card,
if you re-use the debugger CPU). 

No I don't know if that's the right card or not to use. I'm only tossing it
up as another example of what might be used. It is representative of many
boards one might consider. 

The obvious gotcha here is that there are *way* too many choices rather than
too few. I don't know of any boards or CPU's that will do the job without
some "glue" externally. CPU's have a following, just as brands of cars do.
This has turned into a Ford / Chevy debate in the past. That doesn't move
anything forward. There really is no right or wrong, just a lot of personal
preferences with a lot of emotion involved. 

Until a group of people decide they want to do this, I'd leave the CPU
choice wide open. Once you have a willing group, let them work with what
ever they are comfortable with. The bigger decisions and issues are
elsewhere.

Bob  



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Keenan Tims
Sent: Thursday, December 06, 2012 10:38 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer maintained, meaning it's getting hard to find parts.

I've thought on designing a hardware platform to support a GPSDO as
well, but don't have the time-nut or control theory skills (or
equipment) necessary to make the software any good. My hope at the time
was that a build it and they will come approach would solve those
problems, but I haven't had time to make that gamble.

As far as uP choice, Arduino's only saving grace is the pool of existing
'developers' in the amateur community for it - but that's perhaps a big
deal here. It's expensive, doesn't include debug hardware, and is slow
with not many peripherals. I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you want to stay cheap and slow.

Keenan
VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:
> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>
>> If there is one thing I learned, it is that one is never finished
improving
>>  the software. That is why we are time-nuts I guess.
>>
> This is the reason I suggested using the Arduino.  It is so easy to
program
> that MANY people will be able to contribute.  That is my goal, a GPSDO
that
> can be a "living project" that is not dependent on one or a few experts.
> I'd like to see a budget of well under $100, again so that more people can
> contribute and experiment.
>
> A design that can evolve will have just about any performance people want.
>  So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
> and easy to understand and modify.
>


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Re: [time-nuts] GPSDO Alternatives

[paul swed]

Interesting Arthur. I don't think I had a clue you were selling them and
would have paid the difference of what I actually picked one up for. Though
mine was clean and I have not a complaint in the world. Like you I watched
things go up and they were very controlled day by day. At the time it
seemed that all of the units were out of China and I really felt like it
was quite the gamble. It paid off but I was worried about it.
Regards
Paul


On Thu, Dec 6, 2012 at 8:27 AM, Arthur Dent wrote:

> >On Mon, Dec 4, paul swed wrote:
> >Yes sir $139. But boy I have not seen cheap tbolts in  bit. As I recall
> >$260 these days?
> >
> >On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp  wrote:
> >
> >> Hi
> >>
> >> The gotcha is that you go from paying surplus prices to paying new
> prices.
> >> New price to new price, they certainly are cheaper. Not so easy to beat
> a
> >> $100 TBolt on price (if you can find one).
> >>
> >> Bob
> >>
> 
> Comments like these make me smile because they're kind of like the ads you
> used to see for buying $50 jeeps from DOD. Yes, someone at some time in the
> distant past had probably bought one jeep for $50 but these ads continued
> for
> decades like urban legends and a lot of people believed them. As to Tbolt
> prices,
> over the past year or so I had sold close to 200 Tbolts on the popular
> auction site
> at $170 each so I have a pretty good idea what the market was like during
> that time.
> All the Tbolts I had were removed from the original equipment and tested
> by me so
> all the units I sold were clean and worked exactly as they were intended
> to work.
>
> If you watched the price of all the Chinese dealers over this same period
> last year
> they all went up in unison, first to $189, then to $260 as Paul mentioned
> above.
> What you would have noticed if you checked the actual units sold is that
> they were
> not selling any at those prices but buyers were getting their Tbolts from
> me instead.
> I suspect that all the Chinese dealers are basically store front resellers
> for some
> distributor who set the price. As others on this list had commented, the
> condition
> of some of the electronic parts from China indicate that these parts like
> Tbolts and
> OXCOs were removed at some scrapyard by someone who didn't know or care
> what they were but was only interested in throughput and the parts were
> thrown into
> bins for later distribution and sale. Check the photos of bent and/or
> rusted OXCOs
> for listings 170950828042, 170558942064, and 300579197899 to see what I
> mean.
>
> -Arthur
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Re: [time-nuts] GPSDO Alternatives

[Keenan Tims]

As a lurker, I just want to chime in and say that I for one would love
to see an open-source GPSDO implementation. There are quite a few open
hardware designs out there, but as Bob suggests, all the interesting
bits are tied up in the closed-source software they run. And most of
them are no longer maintained, meaning it's getting hard to find parts.

I've thought on designing a hardware platform to support a GPSDO as
well, but don't have the time-nut or control theory skills (or
equipment) necessary to make the software any good. My hope at the time
was that a build it and they will come approach would solve those
problems, but I haven't had time to make that gamble.

As far as uP choice, Arduino's only saving grace is the pool of existing
'developers' in the amateur community for it - but that's perhaps a big
deal here. It's expensive, doesn't include debug hardware, and is slow
with not many peripherals. I'd second the STM32 ARM Cortex platform, or
suggest MSP430 if you want to stay cheap and slow.

Keenan
VE7XEN

On 2012-12-06 1:28 AM, Chris Albertson wrote:
> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>>
>> If there is one thing I learned, it is that one is never finished improving
>>  the software. That is why we are time-nuts I guess.
>>
> This is the reason I suggested using the Arduino.  It is so easy to program
> that MANY people will be able to contribute.  That is my goal, a GPSDO that
> can be a "living project" that is not dependent on one or a few experts.
> I'd like to see a budget of well under $100, again so that more people can
> contribute and experiment.
>
> A design that can evolve will have just about any performance people want.
>  So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
> and easy to understand and modify.
>


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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/6/12 1:06 AM, Chris Albertson wrote:

Yes.   The idea was the simplest GPSDO that can be build with no PCB around
an Arduino.  We already know how to build compllelx and expensive GPSDO.
  That is "too easy".

I think you can use the PWM DAC on the Aruino to drive the OCXO.  The
bandwidth of this signal is "way low" so you can filter the PWM output with
a (say) 1Hz low pass filter.




I would worry about how you'd build that filter to be low noise AND 
suitably filter the PWM output so that there's no leakage of the PWM 
modulation.  Seems it would be easier to hook up a serial interface DAC 
with lots of bits than fool with filters..








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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

There are many marvelous things you can do in software. In some cases you are 
fundamentally limited by the hardware. Regardless of the hardware chosen, the 
effort is 99.99% in other areas. Starting with a hardware platform that lets 
you evolve (even if it's a few dollars more) is generally a good decision. 

Bob

On Dec 6, 2012, at 4:28 AM, Chris Albertson  wrote:

> On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>> 
>> 
>> If there is one thing I learned, it is that one is never finished improving
>> the software. That is why we are time-nuts I guess.
>> 
> 
> This is the reason I suggested using the Arduino.  It is so easy to program
> that MANY people will be able to contribute.  That is my goal, a GPSDO that
> can be a "living project" that is not dependent on one or a few experts.
> I'd like to see a budget of well under $100, again so that more people can
> contribute and experiment.
> 
> A design that can evolve will have just about any performance people want.
> So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
> and easy to understand and modify.
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Simple answer - no, not in a precision part. They are neither high enough 
resolution or deterministic enough to give you very high resolution. 

More complex answer - you can do just about anything if you are willing to 
limit the best possible outcome. With the normal integration times you probably 
will be in the 1x10^-9 to 1x10^-10 noise (ADEV) range.

You would do better with an input capture port. They would be more 
deterministic, but they still have limited resolution. If they are driven by a 
clock multiplier, they likely will have a jitter component on their clock. 
Since low jitter is not a money spec in these low end parts, there can be some 
issues there. 

There are many cheap / simple ways to to the counter. Five dollars will easily 
solve the problem with change left over to pay for breakfast coffee.

Next up on the expanded list is a way to align the pps signals. If you tune 
your OCXO by 0.1 ppm to align them, it will take you 100 days to get to the 
first stage of lock. If you use a CPLD to do that part, you can toss much of 
the counter in with it. You still have change from your five dollars. 

Bob


On Dec 6, 2012, at 4:59 AM, Don Latham  wrote:

> Chris:
> 
>> The question I have again is about a simple phase detector.
> 
> I did ask if the arduino interrupt ports could be used as a phase
> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
> work? I'm simply too new at this to decide.
> 
> Don
> 
> -- 
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
> 
> 
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
> 
> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Don Latham]

Chris:

> The question I have again is about a simple phase detector.

I did ask if the arduino interrupt ports could be used as a phase
detector; one on the GPS and one on the OXCO. Too much jitter? If the 12
MHz clock is too slow, would an 80 MHz clock ARM arduino style processor
work? I'm simply too new at this to decide.

Don

-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

On Wed, Dec 5, 2012 at 2:50 PM,  wrote:
>
>
> If there is one thing I learned, it is that one is never finished improving
>  the software. That is why we are time-nuts I guess.
>

This is the reason I suggested using the Arduino.  It is so easy to program
that MANY people will be able to contribute.  That is my goal, a GPSDO that
can be a "living project" that is not dependent on one or a few experts.
I'd like to see a budget of well under $100, again so that more people can
contribute and experiment.

A design that can evolve will have just about any performance people want.
 So don't worry about if it is 1E-12 or 1E-15.  Just make it transparent
and easy to understand and modify.

-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[WB6BNQ]

Chris,

If you want to understand how to approach the issue, you need to study the Shera
controller system.  It does exactly what you and others are discussing doing.  
It
is relatively simple, straight forward and the HEX file is available to program
the CPU with.  The circuit board is all ready made and available.

The only hard part is the D/A which may be a bit of a problem with respect to 
the
original part.  However, even that may be available from another vender.  If not
there are some similar replacements, but that may require making new boards to
account for the parts being surface mount types.

Do yourself a favor and look at the following URL and download the reprint of 
the
QST article.

http://www.rt66.com/~shera/index_fs.htm

BillWB6BNQ


Chris Albertson wrote:

> Now you can see the problem with designs that require both a PCB and a
> programmed uP.   Most people can't do either of these and those who can
> typically are good at only one.   Then you find someone and after he looses
> interest the project is dead and un-suportable.
>
> So I was thinking of how to build a GPSDO that does not need a programmed
> uP and would be so simple that a PCB would not be needed.  It shoud be
> simple enough that after getting the parts could be built quickly by anyone.
>
> The Arduino has a USB interface and both ADC and DAC and digital IO.  I
> read about the concern about using USB power.  The Arduino can also be
> powered by a 9V battery so it will continue to run if the USB power goes
> away.  Or you can use a power cube (aka "wall wort")  Anyone can program an
> Arduino even if you know nothing about uP.  It is VERY easy and the
> software runs on Mac OS X, Linux and even Windows.
>
> I would use a separate power supply for the OCXO as they take more power
> and this needs to be cleaner than I'd expect USB power to be.
>
> The question I have again is about a simple phase detector.
>
> On Wed, Dec 5, 2012 at 3:28 AM,  wrote:
>
> > Chris
> > There is a low cost solution and I have the input circuit perfect for GPS
> > on a $1 gate array I have boards and am presently using Shera original
> > version.  Would like to buy his version 402NE but have not been able to
> > get a
> > response from him. Have repeatedly asked for help on this list for some
> > one to
> >  step forward to write the uproc. program. No one. The total material cost
> > would  be less than $ 25 PCB included  GPS receiver OCXO or RB would be
> > extra. If  the FE 5680A with RS232 would be used cost is less than $ 15.
> > There
> > are now  PIC's out there that can also do the timing function reducing cost
> > even more but  that will take more smarts.
> > Bert Kehren
> >
> >
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

Don't need anything so complex.   A GPSDO depend on an OCXO that is VERY
stable.  It can be controlled with a very low bandwidth analog signal.

The output from a OCXO is divided down and then the phase of the divided
down 10MHz RF is compared to the PPS and you don't need to even know the
how far apart they are.  All you need to know is "led or lag"  just a one
bit answer.   An XOR gate or a flip flop can tell you that.

If you want to get more fancy you can connect a few temperature sensors to
the Arduino's ADC lines and push those over the USB port along with other
statistics.   Youcan also do things like control the time constants the
software uses via USB also.  But you don't need this.   It can be added
later or not.


On Wed, Dec 5, 2012 at 9:31 AM, Bob Camp  wrote:

> Hi
>
> If the intent is to come up with something in the same league as the TBolt
> there are a few other things you will need:
>
> 1) Something to compare the two pps signals to within 0.1 ns.
> 2) A large amount of code on the control processor (there are a multitude
> of
> special cases ...)
> 3) A large amount of code on a PC to monitor it and control it (like Lady
> Heather)
> 4) A set of standards to compare it to while you train and debug it
> 5) The test gear to collect and analyze the comparison and debug data with
> (you will have many months of data)
> 6) Some sort of control over the feature list. The complexity of 2-5 will
> go
> up significantly each time a nice to have thing is added.
>
> Once you get past step one, the rest of that list dwarf's anything like
> which D/A to use. I'm not at all saying it can't be done. Only that the
> bulk
> of the effort starts after you have the hardware.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Jim Lux
> Sent: Wednesday, December 05, 2012 7:58 AM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] GPSDO Alternatives
>
> On 12/5/12 12:06 AM, Bruce Griffiths wrote:
> > Hal Murray wrote:
> >> albertson.ch...@gmail.com said:
> >>> What is the simplest phase detecter that could work?  I think only
> >>> that, and
> >>> then a duouble oven crystal from eBay, a GPS and and Arduido.
> >> You also need a good D2A to drive the EFC on the osc.
> >>
> >>
> > A synchronous filter of a suitably level translated (CMOS analog switch
> > plus low noise reference) PWM output should work well.
>
> True.. but I think the OP was wanting something that doesn't require
> designing a circuit and building it.
>
> So what you really want is a high performance DAC on a Arduino shield,
> or, alternately, a high performance DAC on a cheap eval board that you
> can easily hook up to an Ardino type processor.
>
> This is a bit trickier..
> Lots of ADC stuff out there, not so much DAC stuff.
>
> http://embeddednewbie.blogspot.com/2011/02/review-of-arduino-dac-solutions.h
> tml
>
> seems to have a number of approaches.  Adafruit has a shield with a
> Microchip MCP4921 12 bit serial dac
>
> here's a 16 bit solution http://www.shaduzlabs.com/article-12.html but
> it's a "build it yourself" solution.
>
> If you're not size/mass/power constrained, you might be able to find an
> inexpensive used programmable power supply.  I do this using a Prologix
> controller driving Agilent E3646 power supplies.. Big, Expensive, etc.
> but it does work.
>
> >>> Yes the Aruino is expensive compared to a bare uP chip but using one,
> >>> I thin
> >>> you could build a GPSDO without a PCB and the Arduino's USB
> >>> connection could
> >>> be usful for power and logging/control.
> >> I wouldn't want to power a GPSDO from USB.  It will get power cycled
> >> every
> >> time I need to work on the logging PC.  Besides, you only get 2.5
> >> watts.  The
> >> oven will probably take more than that during warm-up.
> >>
> >>
> > Bruce
> >
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

Yes.   The idea was the simplest GPSDO that can be build with no PCB around
an Arduino.  We already know how to build compllelx and expensive GPSDO.
 That is "too easy".

I think you can use the PWM DAC on the Aruino to drive the OCXO.  The
bandwidth of this signal is "way low" so you can filter the PWM output with
a (say) 1Hz low pass filter.



On Wed, Dec 5, 2012 at 4:57 AM, Jim Lux  wrote:

> On 12/5/12 12:06 AM, Bruce Griffiths wrote:
>
>> Hal Murray wrote:
>>
>>> albertson.ch...@gmail.com said:
>>>
 What is the simplest phase detecter that could work?  I think only
 that, and
 then a duouble oven crystal from eBay, a GPS and and Arduido.

>>> You also need a good D2A to drive the EFC on the osc.
>>>
>>>
>>>  A synchronous filter of a suitably level translated (CMOS analog switch
>> plus low noise reference) PWM output should work well.
>>
>
> True.. but I think the OP was wanting something that doesn't require
> designing a circuit and building it.


-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

Now you can see the problem with designs that require both a PCB and a
programmed uP.   Most people can't do either of these and those who can
typically are good at only one.   Then you find someone and after he looses
interest the project is dead and un-suportable.

So I was thinking of how to build a GPSDO that does not need a programmed
uP and would be so simple that a PCB would not be needed.  It shoud be
simple enough that after getting the parts could be built quickly by anyone.

The Arduino has a USB interface and both ADC and DAC and digital IO.  I
read about the concern about using USB power.  The Arduino can also be
powered by a 9V battery so it will continue to run if the USB power goes
away.  Or you can use a power cube (aka "wall wort")  Anyone can program an
Arduino even if you know nothing about uP.  It is VERY easy and the
software runs on Mac OS X, Linux and even Windows.

I would use a separate power supply for the OCXO as they take more power
and this needs to be cleaner than I'd expect USB power to be.

The question I have again is about a simple phase detector.




On Wed, Dec 5, 2012 at 3:28 AM,  wrote:

> Chris
> There is a low cost solution and I have the input circuit perfect for GPS
> on a $1 gate array I have boards and am presently using Shera original
> version.  Would like to buy his version 402NE but have not been able to
> get a
> response from him. Have repeatedly asked for help on this list for some
> one to
>  step forward to write the uproc. program. No one. The total material cost
> would  be less than $ 25 PCB included  GPS receiver OCXO or RB would be
> extra. If  the FE 5680A with RS232 would be used cost is less than $ 15.
> There
> are now  PIC's out there that can also do the timing function reducing cost
> even more but  that will take more smarts.
> Bert Kehren
>
>
Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

If you make the leap to - my control processor will be a PC, feature creep is a 
bit easier:

1) The "email when in trouble" feature
2) Wireless network interface
3) Ethernet network interface
4) HDMI video for that 1080P status display
5) Full keyboard and mouse for data entry
6) 16 TB raid array for log files
7) Parallel port for printed running status log
8) Auto update of firmware

That's not saying you don't *also* have another computer as a monitor via 
client / server sort of stuff. 

You may grin at some of the above, but I can easily see all of that winding up 
on somebody's wish list.

Bob




On Dec 5, 2012, at 6:26 PM, Mark Spencer  wrote:

> 
> Over the last two years or so I've put some thought into various home brew 
> alternatives to purchasing a surplus or new GPSDO.  The goal for me would be 
> to have a reference source that combined the short to medium term stability 
> of one of my best OCXO's with the long term stability of a GPSDO.  
> 
> The application would be to serve as a house standard for my test gear and a 
> time server.
> 
> I've envisioned a scheme whereby I'd use an off the shelf time interval 
> counter (probably a surplus HP5370) to continuously compare the OCXO output 
> to the raw 1pps output from a suitable GPS receiver.  (This project would 
> likely give me the excuse I've been looking for to purchase a CNS II GPS 
> receiver that I believe are one of the better choices for raw 1pps accuracy.) 
>  The counter would be connected to a PC via GPIB.
> I'd then need to write the necessary code to periodically steer the OCXO via 
> a to be determined digital to analog converter which in turn would then drive 
> the EFC input on the OCXO.   Rather than implement a software PLL scheme I'd 
> likely start by simply computing the average drift over each day and then 
> simply adjust the OCXO every day or so but eventually I'd expect to implement 
> a PLL scheme in software.I’m hopeful that at first I could implement this 
> in EZGPIB or something similar.   I expect eventually I’d end up coding this 
> in C.
> 
> The main missing piece in the puzzle for me is a suitable DAC that can 
> commanded by a PC (either by RS 232 or GPIB.)  I leave PC's and various 
> pieces of test gear on all the time currently (they help heat my basement lab 
> in the winter) so I'm not worried about dedicating a PC and TIC to this.
> 
> I'd also need a low noise power supply for the DAC and I suspect the 
> performance of the DAC and the pysical interface between the DAC and the OCXO 
> would be the weakest link in this whole system.
> 
> After contemplating the time, effort, and expense to complete a project such 
> as this I've settled for now on simply manually adjusting my OCXO's from time 
> to time and if I am concerned about the drift while using once of them as a 
> reference I simply compare the OCXO in question to a GPSDO while carrying out 
> my other measurement.  The drift of the OCXO can then be accounted for.   
> 
> In reality I can’t imagine having the time to even properly plan let alone 
> implement something like this until I retire and I suspect I’d be lucky if I 
> matched the performance of my best existing GPSDO.   The other alternative 
> that occurs to me is simply connecting a high end OCXO to a Thunderbolt 
> board. 
> 
> Sorry if I come across as overly cynical or pessimistic here (:
> 
> 
>> Message: 3
>> Date: Wed, 05 Dec 2012 22:24:43 +0100
>> From: Volker Esper 
>> To: Discussion of precise time and frequency measurement
>> 
>> Subject: Re: [time-nuts] GPSDO Alternatives
>> Message-ID: <50bfbb9b.7010...@t-online.de>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>> 
>> 
>> Am 05.12.2012 18:31, schrieb Bob Camp:
>>> Hi
>>> 
>>> If the intent is to come up with something in the same
>> league as the TBolt
>>> there are a few other things you will need:
>>> 
>>> 1) Something to compare the two pps signals to within
>> 0.1 ns
>> 
>> Following Ulrich Bangerts suggestions, that a loop time
>> constant should 
>> be at about 3 hours (GPS disciplining an OCXO), do I really
>> need that 
>> resolution? Ok, the more accurate, the better. But the
>> question is: can 
>> I reduce this requirement when using long time constants
>> (1s)? The 
>> ratio then is 10E14...
>> 
>> Volker
>> 
>> 
>> 
>> 
>> --
>> 
> 
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Re: [time-nuts] GPSDO Alternatives

[Mark Spencer]

Over the last two years or so I've put some thought into various home brew 
alternatives to purchasing a surplus or new GPSDO.  The goal for me would be to 
have a reference source that combined the short to medium term stability of one 
of my best OCXO's with the long term stability of a GPSDO.  
 
The application would be to serve as a house standard for my test gear and a 
time server.

I've envisioned a scheme whereby I'd use an off the shelf time interval counter 
(probably a surplus HP5370) to continuously compare the OCXO output to the raw 
1pps output from a suitable GPS receiver.  (This project would likely give me 
the excuse I've been looking for to purchase a CNS II GPS receiver that I 
believe are one of the better choices for raw 1pps accuracy.)  The counter 
would be connected to a PC via GPIB.
I'd then need to write the necessary code to periodically steer the OCXO via a 
to be determined digital to analog converter which in turn would then drive the 
EFC input on the OCXO.   Rather than implement a software PLL scheme I'd likely 
start by simply computing the average drift over each day and then simply 
adjust the OCXO every day or so but eventually I'd expect to implement a PLL 
scheme in software.I’m hopeful that at first I could implement this in 
EZGPIB or something similar.   I expect eventually I’d end up coding this in C.

The main missing piece in the puzzle for me is a suitable DAC that can 
commanded by a PC (either by RS 232 or GPIB.)  I leave PC's and various pieces 
of test gear on all the time currently (they help heat my basement lab in the 
winter) so I'm not worried about dedicating a PC and TIC to this.

I'd also need a low noise power supply for the DAC and I suspect the 
performance of the DAC and the pysical interface between the DAC and the OCXO 
would be the weakest link in this whole system.

After contemplating the time, effort, and expense to complete a project such as 
this I've settled for now on simply manually adjusting my OCXO's from time to 
time and if I am concerned about the drift while using once of them as a 
reference I simply compare the OCXO in question to a GPSDO while carrying out 
my other measurement.  The drift of the OCXO can then be accounted for.   

In reality I can’t imagine having the time to even properly plan let alone 
implement something like this until I retire and I suspect I’d be lucky if I 
matched the performance of my best existing GPSDO.   The other alternative that 
occurs to me is simply connecting a high end OCXO to a Thunderbolt board. 

Sorry if I come across as overly cynical or pessimistic here (:


> Message: 3
> Date: Wed, 05 Dec 2012 22:24:43 +0100
> From: Volker Esper 
> To: Discussion of precise time and frequency measurement
>     
> Subject: Re: [time-nuts] GPSDO Alternatives
> Message-ID: <50bfbb9b.7010...@t-online.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> 
> Am 05.12.2012 18:31, schrieb Bob Camp:
> > Hi
> >
> > If the intent is to come up with something in the same
> league as the TBolt
> > there are a few other things you will need:
> >
> > 1) Something to compare the two pps signals to within
> 0.1 ns
> 
> Following Ulrich Bangerts suggestions, that a loop time
> constant should 
> be at about 3 hours (GPS disciplining an OCXO), do I really
> need that 
> resolution? Ok, the more accurate, the better. But the
> question is: can 
> I reduce this requirement when using long time constants
> (1s)? The 
> ratio then is 10E14...
> 
> Volker
> 
> 
> 
> 
> --
> 

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Re: [time-nuts] GPSDO Alternatives

[SAIDJACK]

Good list Bob,
 
many people underestimate what it takes to make a working,  commercial 
GPSDO, especially one that has to perform in volume and beyond a  single well 
taken care of unit in a Ham shack.
 
Once you have taken care of items 1) and 2), the real work begins. This is  
where our customers get confused some times, they think items 1) and 2) are 
easy  to do, and all that needs to be done to make a working product, and  
they try themselves.
 
We just had someone try connecting the CSAC to a GPS receiver themselves,  
and in their setup they spent two months trying to get it to work before 
they  gave up. The GPS behaved such that the CSAC could not lock onto it  
reliably.
 
This happens quite often because at first sight it looks simple to do, and  
folks like Shera have come up with solutions that are simple and work well, 
but  don't have any bells or whistles.
 
One item often overlooked for example is that every OCXO during a  
production run behaves very differently from the OCXO next to it. The retrace  
time 
is different. The tempco is different. The EFC sensitivity is specified in  
large ranges such as 1ppm to 10ppm, one crystal may jump, another may have 
EFC  hysterisis etc, and the software/hardware has to be able to handle all 
of these  variations without requiring every unit to be fine-tuned by  hand 
during production. And then the OCXO will actually change it's  behavior over 
time due to aging and deminishing retrace error as the unit  is operated 
etc.
 
It's surprising that we still find room to make major improvements to  our 
software 5 years after we sold the first Fury, for example we recently added 
 things like leapsecond prediction/compensation without having an almanac 
loaded  yet, with the help of a time-nut we found a very obscure bug in the 
NXP ARM  processor that was supposed to be fixed years ago but wasn't, and we 
 continuously keep improving and fine-tuning our algorithms and adding more 
 commands/features to it.
 
If there is one thing I learned, it is that one is never finished improving 
 the software. That is why we are time-nuts I guess.
 
bye,
Said
 
 
 
 
In a message dated 12/5/2012 09:29:14 Pacific Standard Time, li...@rtty.us  
writes:

Hi

If the intent is to come up with something in the same  league as the TBolt
there are a few other things you will need:

1)  Something to compare the two pps signals to within 0.1 ns.
2) A large  amount of code on the control processor (there are a multitude 
of
special  cases ...)
3) A large amount of code on a PC to monitor it and control it  (like Lady
Heather)
4) A set of standards to compare it to while you  train and debug it
5) The test gear to collect and analyze the comparison  and debug data with
(you will have many months of data)
6) Some sort of  control over the feature list. The complexity of 2-5 will 
go
up  significantly each time a nice to have thing is added. 

Once you get  past step one, the rest of that list dwarf's anything like
which D/A to  use. I'm not at all saying it can't be done. Only that the 
bulk
of the  effort starts after you have the hardware.  

Bob

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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The TBolt does a resolution somewhere better than 0.1 ns. It (in some cases)
has been shown to hold better than 1 ns stability. That would be hard to do
with a low resolution timing setup.  

Some seem to like 100 seconds as an averaging time, others seem to want
something longer. If you have an Rb, you would certainly want something much
longer (days). Most modern setups step through a number of different time
constants and stop when things get out of hand. The one on the bench in
front of me is sitting at 8,000 seconds.

A 1.0x10^-12 goal is often tossed around for this sort of stuff. A 1 ns
timing accuracy (resolution would need to be better than the accuracy) would
get you to that goal in 1,000 seconds. That's in a perfect world. In a noisy
world you likely would have to wait a bit longer. TBolt to TBolt comparisons
do hit that sort of goal well short of 10,000 seconds (but rarely short of
2,000). 

This all comes down to a "what is your objective?" sort of thing. You can
not simultaneously decide you want to do 10X better than a TBolt, but that
an approach that's 10X worse is ok. (Thus my reference to managing the
feature list). If you are going to price the design against a $130 (or $200)
item, then you should also spec it against the same item. To spec compare it
one way and price compare it another way simply isn't being honest.

Design is so much fun

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Volker Esper
Sent: Wednesday, December 05, 2012 4:25 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives


Am 05.12.2012 18:31, schrieb Bob Camp:
> Hi
>
> If the intent is to come up with something in the same league as the TBolt
> there are a few other things you will need:
>
> 1) Something to compare the two pps signals to within 0.1 ns

Following Ulrich Bangerts suggestions, that a loop time constant should 
be at about 3 hours (GPS disciplining an OCXO), do I really need that 
resolution? Ok, the more accurate, the better. But the question is: can 
I reduce this requirement when using long time constants (1s)? The 
ratio then is 10E14...

Volker


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Re: [time-nuts] GPSDO Alternatives

[Azelio Boriani]

Don't forget that an OCXO needs faster than 10K seconds EFC updates, that's
why you need resolution first.

On Wed, Dec 5, 2012 at 10:24 PM, Volker Esper  wrote:

>
> Am 05.12.2012 18:31, schrieb Bob Camp:
>
>> Hi
>>
>> If the intent is to come up with something in the same league as the TBolt
>> there are a few other things you will need:
>>
>> 1) Something to compare the two pps signals to within 0.1 ns
>>
>
> Following Ulrich Bangerts suggestions, that a loop time constant should be
> at about 3 hours (GPS disciplining an OCXO), do I really need that
> resolution? Ok, the more accurate, the better. But the question is: can I
> reduce this requirement when using long time constants (1s)? The ratio
> then is 10E14...
>
> Volker
>
>
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Re: [time-nuts] GPSDO Alternatives

[Volker Esper]

Am 05.12.2012 18:31, schrieb Bob Camp:

Hi

If the intent is to come up with something in the same league as the TBolt
there are a few other things you will need:

1) Something to compare the two pps signals to within 0.1 ns


Following Ulrich Bangerts suggestions, that a loop time constant should 
be at about 3 hours (GPS disciplining an OCXO), do I really need that 
resolution? Ok, the more accurate, the better. But the question is: can 
I reduce this requirement when using long time constants (1s)? The 
ratio then is 10E14...


Volker


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Re: [time-nuts] GPSDO Alternatives

[Don Latham]

I wonder if two hardware interrupts on the Arduino itself could not be
used for phase locking? There's also an ARM 80 MHz version of the
Arduino package that might be applied, admittedly at higher cost...
Don

Jim Lux
> On 12/5/12 12:06 AM, Bruce Griffiths wrote:
>> Hal Murray wrote:
>>> albertson.ch...@gmail.com said:
 What is the simplest phase detecter that could work?  I think only
 that, and
 then a duouble oven crystal from eBay, a GPS and and Arduido.
>>> You also need a good D2A to drive the EFC on the osc.
>>>
>>>
>> A synchronous filter of a suitably level translated (CMOS analog
>> switch
>> plus low noise reference) PWM output should work well.
>
> True.. but I think the OP was wanting something that doesn't require
> designing a circuit and building it.
>
> So what you really want is a high performance DAC on a Arduino shield,
> or, alternately, a high performance DAC on a cheap eval board that you
> can easily hook up to an Ardino type processor.
>
> This is a bit trickier..
> Lots of ADC stuff out there, not so much DAC stuff.
> http://embeddednewbie.blogspot.com/2011/02/review-of-arduino-dac-solutions.html
>
> seems to have a number of approaches.  Adafruit has a shield with a
> Microchip MCP4921 12 bit serial dac
>
> here's a 16 bit solution http://www.shaduzlabs.com/article-12.html but
> it's a "build it yourself" solution.
>
> If you're not size/mass/power constrained, you might be able to find an
> inexpensive used programmable power supply.  I do this using a Prologix
> controller driving Agilent E3646 power supplies.. Big, Expensive, etc.
> but it does work.
>
 Yes the Aruino is expensive compared to a bare uP chip but using
 one,
 I thin
 you could build a GPSDO without a PCB and the Arduino's USB
 connection could
 be usful for power and logging/control.
>>> I wouldn't want to power a GPSDO from USB.  It will get power cycled
>>> every
>>> time I need to work on the logging PC.  Besides, you only get 2.5
>>> watts.  The
>>> oven will probably take more than that during warm-up.
>>>
>>>
>> Bruce
>>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com



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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

I was hoping somebody had worked out a way around that. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Bruce Griffiths
Sent: Wednesday, December 05, 2012 12:27 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

A low noise sample and hold is still required.

Bruce

Bob Camp wrote:
> Hi
>
> Does the synchronous filter on the PWM  still have a sample and hold in
it, or has somebody come up with a different approach?
>
> Bob
>
> On Dec 5, 2012, at 3:06 AM, Bruce Griffiths
wrote:
>
>
>> Hal Murray wrote:
>>  
>>> albertson.ch...@gmail.com said:
>>>
>>>
>>>> What is the simplest phase detecter that could work?  I think only
that, and
>>>> then a duouble oven crystal from eBay, a GPS and and Arduido.
>>>>
>>>>  
>>> You also need a good D2A to drive the EFC on the osc.
>>>
>>>
>>>
>>>
>> A synchronous filter of a suitably level translated (CMOS analog switch
plus low noise reference) PWM output should work well.
>>  
>>>> Yes the Aruino is expensive compared to a bare uP chip but using one, I
thin
>>>> you could build a GPSDO without a PCB and the Arduino's USB connection
could
>>>> be usful for power and logging/control.
>>>>
>>>>  
>>> I wouldn't want to power a GPSDO from USB.  It will get power cycled
every
>>> time I need to work on the logging PC.  Besides, you only get 2.5 watts.
The
>>> oven will probably take more than that during warm-up.
>>>
>>>
>>>
>>>
>> Bruce
>>
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

If the intent is to come up with something in the same league as the TBolt
there are a few other things you will need:

1) Something to compare the two pps signals to within 0.1 ns.
2) A large amount of code on the control processor (there are a multitude of
special cases ...)
3) A large amount of code on a PC to monitor it and control it (like Lady
Heather)
4) A set of standards to compare it to while you train and debug it
5) The test gear to collect and analyze the comparison and debug data with
(you will have many months of data)
6) Some sort of control over the feature list. The complexity of 2-5 will go
up significantly each time a nice to have thing is added. 

Once you get past step one, the rest of that list dwarf's anything like
which D/A to use. I'm not at all saying it can't be done. Only that the bulk
of the effort starts after you have the hardware. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Jim Lux
Sent: Wednesday, December 05, 2012 7:58 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

On 12/5/12 12:06 AM, Bruce Griffiths wrote:
> Hal Murray wrote:
>> albertson.ch...@gmail.com said:
>>> What is the simplest phase detecter that could work?  I think only
>>> that, and
>>> then a duouble oven crystal from eBay, a GPS and and Arduido.
>> You also need a good D2A to drive the EFC on the osc.
>>
>>
> A synchronous filter of a suitably level translated (CMOS analog switch
> plus low noise reference) PWM output should work well.

True.. but I think the OP was wanting something that doesn't require 
designing a circuit and building it.

So what you really want is a high performance DAC on a Arduino shield, 
or, alternately, a high performance DAC on a cheap eval board that you 
can easily hook up to an Ardino type processor.

This is a bit trickier..
Lots of ADC stuff out there, not so much DAC stuff.
http://embeddednewbie.blogspot.com/2011/02/review-of-arduino-dac-solutions.h
tml

seems to have a number of approaches.  Adafruit has a shield with a 
Microchip MCP4921 12 bit serial dac

here's a 16 bit solution http://www.shaduzlabs.com/article-12.html but 
it's a "build it yourself" solution.

If you're not size/mass/power constrained, you might be able to find an 
inexpensive used programmable power supply.  I do this using a Prologix 
controller driving Agilent E3646 power supplies.. Big, Expensive, etc. 
but it does work.

>>> Yes the Aruino is expensive compared to a bare uP chip but using one,
>>> I thin
>>> you could build a GPSDO without a PCB and the Arduino's USB
>>> connection could
>>> be usful for power and logging/control.
>> I wouldn't want to power a GPSDO from USB.  It will get power cycled
>> every
>> time I need to work on the logging PC.  Besides, you only get 2.5
>> watts.  The
>> oven will probably take more than that during warm-up.
>>
>>
> Bruce
>
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Re: [time-nuts] GPSDO Alternatives

[Bruce Griffiths]

A low noise sample and hold is still required.

Bruce

Bob Camp wrote:

Hi

Does the synchronous filter on the PWM  still have a sample and hold in it, or 
has somebody come up with a different approach?

Bob

On Dec 5, 2012, at 3:06 AM, Bruce Griffiths  wrote:

   

Hal Murray wrote:
 

albertson.ch...@gmail.com said:

   

What is the simplest phase detecter that could work?  I think only that, and
then a duouble oven crystal from eBay, a GPS and and Arduido.

 

You also need a good D2A to drive the EFC on the osc.



   

A synchronous filter of a suitably level translated (CMOS analog switch plus 
low noise reference) PWM output should work well.
 

Yes the Aruino is expensive compared to a bare uP chip but using one, I thin
you could build a GPSDO without a PCB and the Arduino's USB connection could
be usful for power and logging/control.

 

I wouldn't want to power a GPSDO from USB.  It will get power cycled every
time I need to work on the logging PC.  Besides, you only get 2.5 watts.  The
oven will probably take more than that during warm-up.



   

Bruce

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Re: [time-nuts] GPSDO Alternatives

[Jim Lux]

On 12/5/12 12:06 AM, Bruce Griffiths wrote:

Hal Murray wrote:

albertson.ch...@gmail.com said:

What is the simplest phase detecter that could work?  I think only
that, and
then a duouble oven crystal from eBay, a GPS and and Arduido.

You also need a good D2A to drive the EFC on the osc.



A synchronous filter of a suitably level translated (CMOS analog switch
plus low noise reference) PWM output should work well.


True.. but I think the OP was wanting something that doesn't require 
designing a circuit and building it.


So what you really want is a high performance DAC on a Arduino shield, 
or, alternately, a high performance DAC on a cheap eval board that you 
can easily hook up to an Ardino type processor.


This is a bit trickier..
Lots of ADC stuff out there, not so much DAC stuff.
http://embeddednewbie.blogspot.com/2011/02/review-of-arduino-dac-solutions.html

seems to have a number of approaches.  Adafruit has a shield with a 
Microchip MCP4921 12 bit serial dac


here's a 16 bit solution http://www.shaduzlabs.com/article-12.html but 
it's a "build it yourself" solution.


If you're not size/mass/power constrained, you might be able to find an 
inexpensive used programmable power supply.  I do this using a Prologix 
controller driving Agilent E3646 power supplies.. Big, Expensive, etc. 
but it does work.



Yes the Aruino is expensive compared to a bare uP chip but using one,
I thin
you could build a GPSDO without a PCB and the Arduino's USB
connection could
be usful for power and logging/control.

I wouldn't want to power a GPSDO from USB.  It will get power cycled
every
time I need to work on the logging PC.  Besides, you only get 2.5
watts.  The
oven will probably take more than that during warm-up.



Bruce

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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

Does the synchronous filter on the PWM  still have a sample and hold in it, or 
has somebody come up with a different approach?

Bob

On Dec 5, 2012, at 3:06 AM, Bruce Griffiths  wrote:

> Hal Murray wrote:
>> albertson.ch...@gmail.com said:
>>   
>>> What is the simplest phase detecter that could work?  I think only that, and
>>> then a duouble oven crystal from eBay, a GPS and and Arduido.
>>> 
>> You also need a good D2A to drive the EFC on the osc.
>> 
>> 
>>   
> A synchronous filter of a suitably level translated (CMOS analog switch plus 
> low noise reference) PWM output should work well.
>>> Yes the Aruino is expensive compared to a bare uP chip but using one, I thin
>>> you could build a GPSDO without a PCB and the Arduino's USB connection could
>>> be usful for power and logging/control.
>>> 
>> I wouldn't want to power a GPSDO from USB.  It will get power cycled every
>> time I need to work on the logging PC.  Besides, you only get 2.5 watts.  The
>> oven will probably take more than that during warm-up.
>> 
>> 
>>   
> Bruce
> 
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Re: [time-nuts] GPSDO Alternatives

[EWKehren]

Chris
There is a low cost solution and I have the input circuit perfect for GPS  
on a $1 gate array I have boards and am presently using Shera original 
version.  Would like to buy his version 402NE but have not been able to get a  
response from him. Have repeatedly asked for help on this list for some one to 
 step forward to write the uproc. program. No one. The total material cost 
would  be less than $ 25 PCB included  GPS receiver OCXO or RB would be 
extra. If  the FE 5680A with RS232 would be used cost is less than $ 15. There 
are now  PIC's out there that can also do the timing function reducing cost 
even more but  that will take more smarts.
Bert Kehren
 
 
In a message dated 12/4/2012 9:06:26 P.M. Eastern Standard Time,  
albertson.ch...@gmail.com writes:

With the  price of T-Bolts now higher, does it make sense to build your  own
GPSDO?

What is the simplest phase detecter that could  work?  I think only that,
and then a duouble oven crystal from eBay, a  GPS and and Arduido.

Yes the Aruino is expensive compared to a bare uP  chip but using one, I
thin you could build a GPSDO without a PCB and the  Arduino's USB connection
could be usful for power and  logging/control.

If ther phase detector where simple enough it could be  build on a prototype
board the fits on top of the Arduino.

There are  some other designs but because programming a uP and making a PCB
seem to be  rare skills that job tends to fall on one person.  Anyone can
program  an Arduino and with out need of a PCB the entire design could be
puted on a  web page and the replicated with common parts.


On Tue, Dec 4, 2012  at 4:01 PM, Bob Camp  wrote:

>  Hi
>
> I would guess that HP/Agilent/Symmetricom and Trimble made  100X more
> GPSDO's than the next five people in the business combined  over the 1995 
to
> 2005 period.
>
> Bob
>
> On  Dec 4, 2012, at 10:26 AM, paul swed   wrote:
>
> > Al
> > I like the truetime products. In  general easy to understand and last a
> long
> > time.
>  > But there never seemed to be that many. Sure they were used in
>  broadcasting
> > and maybe power. But the others like the 3801 and  tbolt were used in
> telco
> > and mobile apps so there were  10,000s turned out and thats why we get
> them
> > for cheap. I  simply never see the truetime dc60 or gps units around.
> Though
>  > I have my stock of dc468 sat clocks. :-) Working. I hacked a goes  sat
> > replacement 3-4 years ago.
> > That said some of the  older gps technology is a bit slippery on exactly
> how
> >  good they are.
> > So for perhaps amateur purposes they are totally  fine but when you 
start
> > comparing to a Tbolt or 3801 various  behaviors apear.
> > Odetics GPStars as an example slip cycles on  purpose. Its a mode you 
can
> > set and by default is how they are  set.
> > For what they were intended for they are perfect. But at  least 1 X10
> poorer
> > then other devices. Its not at all  broken. It was a general time piece
> for
> > radio networks.  Give or take 500 ms.
> > Regards
> > Paul
> >  WB8TSL
> >
> >
> > On Tue, Dec 4, 2012 at 9:58 AM,  Al Wolfe  wrote:
> >
>  >>   Most of the choices I've seen here mention the Tbolts,  3801, 3805,
> etc,
> >> but I have never seen anyone mention  the TrueTime XL-AK. It advertises
> 40
> >> nsec 1 pps.  Frequency as 1 x 10-12 per day. I have one and it seems to
>  work
> >> well but have no way to test it against anything else  yet. It has four
> each
> >> 10 MHz sine output that I have  been using for house sync for HP3586,
> >> HP8924c, PTS160,  etc.
> >>
> >>   So how does the TrueTime  compare to other GPSDO's?
> >>
> >> Al, K9SI
>  >>
> >>  __**_
> >> time-nuts  mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to  https://www.febo.com/cgi-bin/**
> >>  mailman/listinfo/time-nuts<
>  https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> >>  and follow the instructions there.
> >>
> >  ___
> > time-nuts mailing  list -- time-nuts@febo.com
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-- 

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Redondo Beach,  California
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Re: [time-nuts] GPSDO Alternatives

[Bruce Griffiths]

Hal Murray wrote:

albertson.ch...@gmail.com said:
   

What is the simplest phase detecter that could work?  I think only that, and
then a duouble oven crystal from eBay, a GPS and and Arduido.
 

You also need a good D2A to drive the EFC on the osc.


   
A synchronous filter of a suitably level translated (CMOS analog switch 
plus low noise reference) PWM output should work well.

Yes the Aruino is expensive compared to a bare uP chip but using one, I thin
you could build a GPSDO without a PCB and the Arduino's USB connection could
be usful for power and logging/control.
 

I wouldn't want to power a GPSDO from USB.  It will get power cycled every
time I need to work on the logging PC.  Besides, you only get 2.5 watts.  The
oven will probably take more than that during warm-up.


   

Bruce

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Re: [time-nuts] GPSDO Alternatives

[Hal Murray]

albertson.ch...@gmail.com said:
> What is the simplest phase detecter that could work?  I think only that, and
> then a duouble oven crystal from eBay, a GPS and and Arduido. 

You also need a good D2A to drive the EFC on the osc.


> Yes the Aruino is expensive compared to a bare uP chip but using one, I thin
> you could build a GPSDO without a PCB and the Arduino's USB connection could
> be usful for power and logging/control. 

I wouldn't want to power a GPSDO from USB.  It will get power cycled every 
time I need to work on the logging PC.  Besides, you only get 2.5 watts.  The 
oven will probably take more than that during warm-up.


-- 
These are my opinions.  I hate spam.




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Re: [time-nuts] GPSDO Alternatives

[Chris Albertson]

With the price of T-Bolts now higher, does it make sense to build your own
GPSDO?

What is the simplest phase detecter that could work?  I think only that,
and then a duouble oven crystal from eBay, a GPS and and Arduido.

Yes the Aruino is expensive compared to a bare uP chip but using one, I
thin you could build a GPSDO without a PCB and the Arduino's USB connection
could be usful for power and logging/control.

If ther phase detector where simple enough it could be build on a prototype
board the fits on top of the Arduino.

There are some other designs but because programming a uP and making a PCB
seem to be rare skills that job tends to fall on one person.  Anyone can
program an Arduino and with out need of a PCB the entire design could be
puted on a web page and the replicated with common parts.


On Tue, Dec 4, 2012 at 4:01 PM, Bob Camp  wrote:

> Hi
>
> I would guess that HP/Agilent/Symmetricom and Trimble made 100X more
> GPSDO's than the next five people in the business combined over the 1995 to
> 2005 period.
>
> Bob
>
> On Dec 4, 2012, at 10:26 AM, paul swed  wrote:
>
> > Al
> > I like the truetime products. In general easy to understand and last a
> long
> > time.
> > But there never seemed to be that many. Sure they were used in
> broadcasting
> > and maybe power. But the others like the 3801 and tbolt were used in
> telco
> > and mobile apps so there were 10,000s turned out and thats why we get
> them
> > for cheap. I simply never see the truetime dc60 or gps units around.
> Though
> > I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat
> > replacement 3-4 years ago.
> > That said some of the older gps technology is a bit slippery on exactly
> how
> > good they are.
> > So for perhaps amateur purposes they are totally fine but when you start
> > comparing to a Tbolt or 3801 various behaviors apear.
> > Odetics GPStars as an example slip cycles on purpose. Its a mode you can
> > set and by default is how they are set.
> > For what they were intended for they are perfect. But at least 1 X10
> poorer
> > then other devices. Its not at all broken. It was a general time piece
> for
> > radio networks. Give or take 500 ms.
> > Regards
> > Paul
> > WB8TSL
> >
> >
> > On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe  wrote:
> >
> >>   Most of the choices I've seen here mention the Tbolts, 3801, 3805,
> etc,
> >> but I have never seen anyone mention the TrueTime XL-AK. It advertises
> 40
> >> nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to
> work
> >> well but have no way to test it against anything else yet. It has four
> each
> >> 10 MHz sine output that I have been using for house sync for HP3586,
> >> HP8924c, PTS160, etc.
> >>
> >>   So how does the TrueTime compare to other GPSDO's?
> >>
> >> Al, K9SI
> >>
> >> __**_
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> >> mailman/listinfo/time-nuts<
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> >> and follow the instructions there.
> >>
> > ___
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> > To unsubscribe, go to
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> > and follow the instructions there.
>
>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

I would guess that HP/Agilent/Symmetricom and Trimble made 100X more GPSDO's 
than the next five people in the business combined over the 1995 to 2005 period.

Bob

On Dec 4, 2012, at 10:26 AM, paul swed  wrote:

> Al
> I like the truetime products. In general easy to understand and last a long
> time.
> But there never seemed to be that many. Sure they were used in broadcasting
> and maybe power. But the others like the 3801 and tbolt were used in telco
> and mobile apps so there were 10,000s turned out and thats why we get them
> for cheap. I simply never see the truetime dc60 or gps units around. Though
> I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat
> replacement 3-4 years ago.
> That said some of the older gps technology is a bit slippery on exactly how
> good they are.
> So for perhaps amateur purposes they are totally fine but when you start
> comparing to a Tbolt or 3801 various behaviors apear.
> Odetics GPStars as an example slip cycles on purpose. Its a mode you can
> set and by default is how they are set.
> For what they were intended for they are perfect. But at least 1 X10 poorer
> then other devices. Its not at all broken. It was a general time piece for
> radio networks. Give or take 500 ms.
> Regards
> Paul
> WB8TSL
> 
> 
> On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe  wrote:
> 
>>   Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc,
>> but I have never seen anyone mention the TrueTime XL-AK. It advertises 40
>> nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work
>> well but have no way to test it against anything else yet. It has four each
>> 10 MHz sine output that I have been using for house sync for HP3586,
>> HP8924c, PTS160, etc.
>> 
>>   So how does the TrueTime compare to other GPSDO's?
>> 
>> Al, K9SI
>> 
>> __**_
>> 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.
>> 
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Re: [time-nuts] GPSDO Alternatives

[paul swed]

Al
I like the truetime products. In general easy to understand and last a long
time.
But there never seemed to be that many. Sure they were used in broadcasting
and maybe power. But the others like the 3801 and tbolt were used in telco
and mobile apps so there were 10,000s turned out and thats why we get them
for cheap. I simply never see the truetime dc60 or gps units around. Though
I have my stock of dc468 sat clocks. :-) Working. I hacked a goes sat
replacement 3-4 years ago.
That said some of the older gps technology is a bit slippery on exactly how
good they are.
So for perhaps amateur purposes they are totally fine but when you start
comparing to a Tbolt or 3801 various behaviors apear.
Odetics GPStars as an example slip cycles on purpose. Its a mode you can
set and by default is how they are set.
For what they were intended for they are perfect. But at least 1 X10 poorer
then other devices. Its not at all broken. It was a general time piece for
radio networks. Give or take 500 ms.
Regards
Paul
WB8TSL


On Tue, Dec 4, 2012 at 9:58 AM, Al Wolfe  wrote:

>Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc,
> but I have never seen anyone mention the TrueTime XL-AK. It advertises 40
> nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work
> well but have no way to test it against anything else yet. It has four each
> 10 MHz sine output that I have been using for house sync for HP3586,
> HP8924c, PTS160, etc.
>
>So how does the TrueTime compare to other GPSDO's?
>
> Al, K9SI
>
> __**_
> 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.
>
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Re: [time-nuts] GPSDO Alternatives

[Al Wolfe]

   Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, 
but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 
nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work 
well but have no way to test it against anything else yet. It has four each 
10 MHz sine output that I have been using for house sync for HP3586, 
HP8924c, PTS160, etc.


   So how does the TrueTime compare to other GPSDO's?

Al, K9SI 



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Re: [time-nuts] GPSDO Alternatives

[paul swed]

Indeed and it seems the 3801s have a premium above the Tbolts these days.
I have both.
I picked up the tbolt much later and I simply waited for a good deal to
show up. It took a year. I wasn't in a hurry.
But that said I am still interested in the newer versions if they are
reasonable in cost.
Regards
Paul

On Tue, Dec 4, 2012 at 7:32 AM, Bob Camp  wrote:

> Hi
>
> They certainly aren't flooding the market these days the way they were a
> few years ago. I suspect you still can get them "cheap" if you are willing
> to wait a while. Even the two hundred dollar price is pretty good compared
> to the price of a newly manufactured OCXO based GPSDO.
>
> Bob
>
> On Dec 3, 2012, at 9:56 PM, paul swed  wrote:
>
> > Yes sir $139. But boy I have not seen cheap tbolts in  bit. As I recall
> > $260 these days?
> >
> > On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp  wrote:
> >
> >> Hi
> >>
> >> The gotcha is that you go from paying surplus prices to paying new
> prices.
> >> New price to new price, they certainly are cheaper. Not so easy to beat
> a
> >> $100 TBolt on price (if you can find one).
> >>
> >> Bob
> >>
> >> On Dec 3, 2012, at 8:50 PM, Magnus Danielson <
> mag...@rubidium.dyndns.org>
> >> wrote:
> >>
> >>> On 12/04/2012 02:44 AM, paul swed wrote:
>  Hmmm new and better.
>  That means better stability, noise, lower power, lower heat, for less
> >> and
>  works with lady heather? :-)
>  I can hope.
> >>>
> >>> Mostly cheaper actually. Better GPS to start with, probably. Lower
> >> power, most probably.
> >>>
> >>> We should discuss if we can't have Lady Heather take a larger
> >> client-base of GPSDOs. There are so many peaces in there that would be
> nice
> >> to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc.
> >>>
> >>> Cheers,
> >>> Magnsu
> >>>
> >>> ___
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> >>
> >>
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

They certainly aren't flooding the market these days the way they were a few 
years ago. I suspect you still can get them "cheap" if you are willing to wait 
a while. Even the two hundred dollar price is pretty good compared to the price 
of a newly manufactured OCXO based GPSDO.

Bob

On Dec 3, 2012, at 9:56 PM, paul swed  wrote:

> Yes sir $139. But boy I have not seen cheap tbolts in  bit. As I recall
> $260 these days?
> 
> On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp  wrote:
> 
>> Hi
>> 
>> The gotcha is that you go from paying surplus prices to paying new prices.
>> New price to new price, they certainly are cheaper. Not so easy to beat a
>> $100 TBolt on price (if you can find one).
>> 
>> Bob
>> 
>> On Dec 3, 2012, at 8:50 PM, Magnus Danielson 
>> wrote:
>> 
>>> On 12/04/2012 02:44 AM, paul swed wrote:
 Hmmm new and better.
 That means better stability, noise, lower power, lower heat, for less
>> and
 works with lady heather? :-)
 I can hope.
>>> 
>>> Mostly cheaper actually. Better GPS to start with, probably. Lower
>> power, most probably.
>>> 
>>> We should discuss if we can't have Lady Heather take a larger
>> client-base of GPSDOs. There are so many peaces in there that would be nice
>> to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc.
>>> 
>>> Cheers,
>>> Magnsu
>>> 
>>> ___
>>> 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.
>> 
>> 
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>> and follow the instructions there.
>> 
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Re: [time-nuts] GPSDO Alternatives

[paul swed]

Yes sir $139. But boy I have not seen cheap tbolts in  bit. As I recall
$260 these days?

On Mon, Dec 3, 2012 at 9:12 PM, Bob Camp  wrote:

> Hi
>
> The gotcha is that you go from paying surplus prices to paying new prices.
> New price to new price, they certainly are cheaper. Not so easy to beat a
> $100 TBolt on price (if you can find one).
>
> Bob
>
> On Dec 3, 2012, at 8:50 PM, Magnus Danielson 
> wrote:
>
> > On 12/04/2012 02:44 AM, paul swed wrote:
> >> Hmmm new and better.
> >> That means better stability, noise, lower power, lower heat, for less
> and
> >> works with lady heather? :-)
> >> I can hope.
> >
> > Mostly cheaper actually. Better GPS to start with, probably. Lower
> power, most probably.
> >
> > We should discuss if we can't have Lady Heather take a larger
> client-base of GPSDOs. There are so many peaces in there that would be nice
> to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc.
> >
> > Cheers,
> > Magnsu
> >
> > ___
> > 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.
>
>
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Re: [time-nuts] GPSDO Alternatives

[Bob Camp]

Hi

The gotcha is that you go from paying surplus prices to paying new prices. New 
price to new price, they certainly are cheaper. Not so easy to beat a $100 
TBolt on price (if you can find one).

Bob

On Dec 3, 2012, at 8:50 PM, Magnus Danielson  wrote:

> On 12/04/2012 02:44 AM, paul swed wrote:
>> Hmmm new and better.
>> That means better stability, noise, lower power, lower heat, for less and
>> works with lady heather? :-)
>> I can hope.
> 
> Mostly cheaper actually. Better GPS to start with, probably. Lower power, 
> most probably.
> 
> We should discuss if we can't have Lady Heather take a larger client-base of 
> GPSDOs. There are so many peaces in there that would be nice to be used with 
> a larger set of tools, like G12, Z12s, Z3801/3815 etc.
> 
> Cheers,
> Magnsu
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] GPSDO Alternatives

[Magnus Danielson]

On 12/04/2012 02:44 AM, paul swed wrote:

Hmmm new and better.
That means better stability, noise, lower power, lower heat, for less and
works with lady heather? :-)
I can hope.


Mostly cheaper actually. Better GPS to start with, probably. Lower 
power, most probably.


We should discuss if we can't have Lady Heather take a larger 
client-base of GPSDOs. There are so many peaces in there that would be 
nice to be used with a larger set of tools, like G12, Z12s, Z3801/3815 etc.


Cheers,
Magnsu

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