[time-nuts] GPS DO Alternatives

Chris Albertson albertson.chris at gmail.com
Sat Dec 8 18:59:54 UTC 2012

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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