[ntp:questions] Re: Good GPS for attic?
jpp at cloudview.com
Thu Mar 10 06:17:56 UTC 2005
Brad Knowles wrote:
> At 6:26 PM -0800 2005-03-09, roy wrote:
>> Isn't this a bit misrepresented? The way I read his web page, he
>> replaced the standard, 39 cent crystal with a $1,500 rubidium frequency
>> standard. No wonder it keeps time so well!
> No, the real key to PHK's work was taking one of the most accurate
> off-the-shelf/kit GPS units designed to provide accurate time, combining
> that with a host that had very low latency to servicing the necessary
> interrupts, and only then did he add the Rubidium clock. He would not
> have lost too much by going with an OCXO or even a TCXO.
> If you want that same level of accuracy and precision in a
> commercial unit, you probably won't be able to get it. If you can,
> you'll spend enough money that you could have bought at least one decent
> car or made a down payment on a house.
That said for $85 you can get a Garmin GPS18 lvc which claims +/- 1us
(modulo the stability of your system and the latency of your PPS drivers).
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