[time-nuts] GPS module recommendation for Pi timing

[Brian Lloyd]

On Fri, Mar 13, 2020 at 8:49 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> If you always operate in fixed locations, your chances of seeing a slip
> are not that high. The original post question and reference here were to
> timing in a *mobile* situation.
>

Thank you all for your inputs. Here is a little more data, prompted by
comments and questions. (Some of this I wasn't thinking about at first.)

I realized that, while I expect the majority of units to be stationary with
the ability to properly position an antenna, there is a chance that one or
more of the units may be mobile. Regardless of mobility, the purpose will
be time and frequency reference, not position. Does that change my choice
of device?

Some of the units may have access to the Internet and I could run NTP on
them but the majority will be using GPS as the single stand-alone source of
UTC. The goal is for all the units to be sync'd to UTC as they need to
perform repetitive functions concurrently.

The starting point for me was going to be the Ublox LEA-M8T because it is
current generation and Ublox offers a common footprint so that, if
production runs into the future, there will be newer modules that can be
dropped onto the same board. I want the second output to use as a 10MHz
reference. I have need for a 3e-7 accuracy 10MHz frequency reference in
some cases and that looked like it would do what is needed without going
full-on GPSDOCXO.

So is my first choice of the Ublox LEA-M8T a good one or should I be
looking at other units. While I don't want to spend $50(us) on a receiver,
if it does the best job, it will fit the budget and that extra timing
output I can use to generate 10MHz is quite attractive.

-- 



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
brian at lloyd.aero
+1.210.802-8FLY (1.210.802-8359)