[time-nuts] GPSDO Alternatives

Chris Albertson albertson.chris at gmail.com
Wed Dec 5 02:05:53 UTC 2012


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 <lists at rtty.us> 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 <paulswedb at gmail.com> 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 <alw.k9si at gmail.com> 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
> >>
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-- 

Chris Albertson
Redondo Beach, California


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