[time-nuts] GPS DO Alternatives

[Bob Camp]

Hi

Have an alarm go off on your PC and do the correction once a month.

Bob

On Dec 8, 2012, at 8:56 PM, Chris Albertson <albertson.chris at gmail.com> wrote:

> So the goal then is automate the process, not to make it better.  I figure
> once you have an easy-to-modify and easy-to-replicate design up and running
> then with many people able to experiment the performance will improve.
> 
> You can almost not count the cost of the Arduino.  This is a self contained
> part that can be used in many projects.  Same with a 12VDC power supply.
> Lots of people like to play with these and have them already.
> 
> So,....  as for performance, let's just say for not that it only has to
> work as well as one could do by hand and eye and a 'scope.  Let's say 10E-8
> 
> 
> What if I use a flip flop.  The PPS from the GPS connects to the "set"
> input of the FF and also to the Arduino interrupt.   The output of the OCXO
> goes to the reset pin of the same FF.
> 
> The interrupt handler reads the value of the FF.  It will be either 1 or 0
> depending if the phase of the OCXO leads or lags the phase of the PPS.  The
> software will try to keep the FF average value at exactly 0.500
> 
> 
> 
> 
> On Sat, Dec 8, 2012 at 4:25 PM, Bob Camp <lists at rtty.us> wrote:
> 
>> Hi
>> 
>> A standard that is good to "8 digits" can be done manually. That's far
>> cheaper than your goal and the software is totally open source. It can be
>> done with off the shelf parts and no wiring at all.
>> 
>> Problem solved?
>> 
>> I suspect not….
>> 
>> Bob
>> 
>> On Dec 8, 2012, at 1:59 PM, Chris Albertson <albertson.chris at gmail.com>
>> wrote:
>> 
>>> On Sat, Dec 8, 2012 at 9:30 AM, <johncroos at aol.com> wrote:
>>> 
>>>> Hello all -
>>>> 
>>>> "People talk about good deals on Thunderbolts but I have
>>>> yet to see one.  It seems peak Thunderbolt passed before I was
>>>> seriously looking."
>>>> 
>>>> 
>>>> *The box you put it in - suspending it above the bench on inspirational
>>>> thought probably
>>>> will not work. A nice box is easily $ 50.00 so who cares about adding
>>>> another flip flop or
>>>> counter at 25 cents each.
>>> 
>>> 
>>> 
>>> The goal, well my goal is to build a GPSDO to this set of requirements
>>> 
>>> 1) well under 1/2 the cost of the t-bolt.
>>> 2) can be made with common parts and skills most people have
>>> 3) is completely modifiable (open source software)
>>> 
>>> So #1 above means you use a low cost box, perhaps the case and old CDROM
>>> was once housed in or maybe you gut and old PC chassis
>>> 
>>> #2 pretty much means you have to keep theparts cound way down.  Yes a
>> chip
>>> might cost only $1 but as soon as you get more then about three of those
>> 25
>>> cent cips you need a PCB.   PCB making is not a common everyday skill so
>> #2
>>> means a way-low parts count
>>> 
>>> #3 means the uP is gong to have to come with a very easy to use and free
>>> open source toolchain.  Adruino is like that, there are others, but a
>> bare
>>> uP chip is not going to work
>>> 
>>> 
>>> You are right that one way to engineer a product is to first set
>>> performance numbers.   But another more common way is to first identify a
>>> target customer and then set a target price.   In this case the target
>>> customer is a hobbyist with only basic skills who wants a low cost easy
>> to
>>> build GPSDO that has can understand and modify himself.
>>> 
>>> Next with those very hard to meet requirements (low cost, low parts
>> count,
>>> simple to build) we can ask if the exected perfomance is "good enough"
>>> What is good enough.  I'd say if you could use the GPSDO a a local
>>> frequency standard for a counter that has 8 digits you are doing "well
>>> enough".  If you can get to 10 digital it is pretty good
>>> 
>>> --
>>> 
>>> Chris Albertson
>>> Redondo Beach, California
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>> 
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> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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