[OT] Splitting PPS?

[Gary E. Miller]

Yo Richard!

On Wed, 13 Nov 2019 11:38:40 -0600
Richard Laager via devel <devel at ntpsec.org> wrote:

> The tentative plan is to upgrade/reinstall Ubuntu, switch to NTPsec,
> and deploy NTS. That's all easy.

Yup.

> It'd be nice if we could also replace the dead GPS master clock with a
> directly connected GPS receiver, so we get PPS into the server (e.g.
> via a serial port). That would make them stratum 1.

Yup.

> For this project, we could buy an equivalent current
> generation EVK-M8T for $250 from e.g. Digi-Key.

I think you have an extra zero on there.  I do this for about $25.

> Is there an easy way to split an RS232 level PPS (and optionally the
> GPS's TX for gpsd) into three systems?

Sure, real RS-232 has a lot of drive power to get the +/-12V to work.

> What is the most cost-effective way to create three stratum 1 servers?

The T version u-blox are way overkill for a stratum 1.  A simple u-blox
NEO-M8N for $10 will do.  Then $5 for a TTL to RS-232 converter.

Get one of these NEO-M8N for $7:

https://www.ebay.com/itm/Replacement-NEO-M8N-GPS-BDS-Dual-mode-Module-Flight-Control-Satellite-ATGM336H/182622902135

Get the 5V for it by cuting up an old USB cable.

Then convert the TTL TX/RX to RS-232, with connector, for $3:

https://www.ebay.com/itm/RS232-SP3232-TTL-to-male-serial-port-TTL-to-RS232-level-conversion-serial-S6J6/112608133090

Add a GHz power divider for $10 and run all 3 on one antenna.

I do it all the time.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin
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