[time-nuts] GPSDO Comparisons

[J. L. Trantham]

First point is a question, what are you going to use it for?  Stable
reference?  Precision timing?  Etc.

Second point is, in essence, 'a man with one watch knows what time it is, a
man with two (or more) watches is never really quite sure'.

That said, I would opt for the cheapest that will satisfy your needs.  I
would also consider a second (or third) unit, just to help you make sure the
first is working.

The major differences have to do with the OCXO's in the various units and
how well they perform.  The rest is 'control circuitry' and the ability to
monitor it.

I have Tbolt's, Z3816A's, and a Z3805A along with some CS units.  Clearly
overkill on my part but much fun.

Hope this helps.

Joe



-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Ziggy
Sent: Wednesday, October 20, 2010 3:08 PM
To: time-nuts at febo.com
Subject: [time-nuts] GPSDO Comparisons


I did some searching (perhaps ineffectively) of the archives, looking 
for some discussion of the merits of the different GPSDO products that 
we commonly see on auction sites. I've seen some discussions of 
individual models, but nothing that really discusses the differences, 
and why one unit may be superior to another. I'm a newcomer, so please 
be patient with my silly questions :)

For example, what are the relative merits of the HP units? There are 
different vintages HP Z3801A, Z3805A, Z3815A, etc. and datasheets are 
available, but what  difference is there when using the output from 
these different models? For example, the Z3801A has a 6 channel GPS 
receiver. The Samsung/Symmetricom Z3805A we see out there has a 16 
channel receiver. What is the difference when it comes to practical 
usage of these two different units? Does tracking 10 or 12 satellites 
provide a benefit over tracking 6?

Then there are the different manufacturers. There are the HP units, the 
Alcatel-Lucent units (also of varying vintage), Trimble Thunderbolts, 
and others. Again, when it comes to practical usage is there any  
difference between these? Is there any value in paying the premium for a 
Z3805A over a Thunderbolt? (Above the plug and play aspects.) I can get 
an older ALU unit with both GPSDO and Ru units for $100. How am I 
hurting myself with that purchase?

There is certainly more public information available for some vendors 
and models than others. The software like Lady Heather or GPS Control 
provide a lot of information, and for the less popular units there is no 
such software option. Under what circumstances would that be a handicap?

I freely admit I'm ignorant, but I'm not thin skinned. I'm just not 
aware yet of the factors to be considered when answering the questions 
above. Any comments would be appreciated.

Thanks

Paul

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