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

[Larry Gadallah]

Hi Bob:

I had to LoL (laugh out loud) when I read your message. I definitely
get what you are saying, but it amused me to no end; When I got my
first ham license, one of my elmers was the regional distributor for
Drake, so I announced my intention to take my hard earned cash and
purchase a shiny new Drake receiver.

The local elders croaked out: "You don't want to do that. You won't
learn anything. You should build your own radio from scratch and gain
some valuable experience." So, here I am some 40 years later, getting
the exact opposite suggestion. I guess it's true that amateur radio in
many respects has become merely a tiny slice of the consumer
electronics market.

But back to the question at hand: From a purely pragmatic point of
view, I've been collecting parts for this project for a decade, and
I'm just thinking that I should either do it, or dispose of the stuff
and forget about it. You are probably right about needing some
sophisticated equipment, and we'll see where that leads.

Seems to me that this is another reality of DIY ham radio these days:
75 years ago, you just needed a (wooden) bread board, some brass
screws, and a tube. Now you need spectrum analyzers, SMT microscopes,
fantastic eyesight and hand-eye coordination, it just isn't as easy
anymore.

73,

On Tue, 15 Feb 2022 at 10:25, Bob kb8tq <kb8tq at n1k.org> wrote:
>
> 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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-- 
Larry Gadallah, lgadallah AT gmail DOT com
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