[time-nuts] Freq cal to 1ppm without GPSDO

Chris Albertson albertson.chris at gmail.com
Thu Feb 17 17:13:00 UTC 2011


On Wed, Feb 16, 2011 at 11:43 PM, David J Taylor
<david-taylor at blueyonder.co.uk> wrote:

> Would you count these as nearer a "working system"?  Only needs USB power,
> and includes the antenna and cable.
>
>  http://www.sureelectronics.net/goods.php?id=99
>
> I'm still waiting for mine to arrive.

The advantage of the Oncore GPS is that it is well documented.
Motorola wrote some detailed manuals in good English that are on-line.
 The Sure units are more "ready to use" but come with typical Chinese
eBay documentation.   Not saying which to get.  Either should work.
It's not hard to set up an Oncore GPS, just power it and interface it
to RS232.  the MAX232 chip makes that part easy and you can find DB9
connectors with the chip attached for about $4.

But those Thunderbolt units are selling for $100 and are GPSDXOs with
very good specs and only need power and an Antenna

For many people the Antenna is that hardest part.  You need a clear
view of the sky and if it snows at your location some setup that keeps
it clear of snow and then you need a cable from the Antenna back to
the GPS.  Running a wire out an open windows works for a test but not
long term,  Long tern you'd want a pole mount antenna up on the roof.
  So  a few voltage regulators and interface chips is not much work
compared to a permanent antenna setup

One thing to look at when choosing a GPS is software.  Maybe you are
going to run an NTP server or you need software that runs on Linux.
Or maybe you plan to buy several GPS receivers and want software that
can run all of them.

Always the old joke is true:  A man who has one GPS knows what time it
is, A man with two is never sure.  So you buy three.


-- 
=====
Chris Albertson
Redondo Beach, California



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