[time-nuts] Re: Current-day GPS timing receivers

[Bob kb8tq]

Hi

First question would be “why?” ( or more properly, what are you trying
to accomplish? / what are the project goals? )

You can buy any one of a number of GPSDO’s on eBay for very little money.
They come in a range of “flavors” from a range of suppliers. You can
get OCXO based units. You can get ones based on Rb’s. 

Setting up the instrumentation to evaluate a GPSDO design is a bit 
complicated. Things like atomic clocks and phase noise / short term
stability analyzers tend to creep into the lab as a result. That’s not a 
bad thing. One does need *something* to fill up all that empty bench
space :) :)

I would suggest that this all puts a project with a goal of “I want to save
money” into the “unlikely” category. If you want higher performance than
what you can easily buy, that will require pretty good instrumentation. 

Basic choices these days:

uBlox makes a variety of modules. Some are single band, some are multi 
band. Multi band offers some performance advantages. It also costs more. 

The Mosaic-T from Septentrio appears to be the top of the heap right now
in terms of mulit band / multi GNSS timing modules.  It has the advantage
of being able to work directly with a 10 MHz input and eliminate some of 
the sawtooth correction “stuff”. 

Best guess is that going from a from scratch “idea” to something that you 
can fully demonstrate works very well is a couple of year sort of project.

None of this is to say don’t do it. The only point is to recognize what you
are signing up for before you dive down the rabbit hole. 

Bob


> On Feb 14, 2022, at 9:22 PM, Larry Gadallah <lgadallah at gmail.com> wrote:
> 
> I'm thinking of reviving a long dead project to build a GPSDO. The last
> time I looked, state of the art for GPS receivers was things like the
> Motorola Oncore UT+ or the Trimble Resolution T. It's been 10 years (at
> least). What better options, if any, are available today?
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