[time-nuts] SRS PRS10 RFC

[Poul-Henning Kamp]

--------
In message <0a9f6701-42d5-7553-8ea9-980899936c5f at intercat.com.br>, Luiz Alberto Saba writes:

>1. Power supply. 24 V switched is OK or the classic 
>transformer/bridge/huge capacitors/regulator is best?

A good switched PSU is better than a mediocre linear PSU these days.

>2. Heat. Do I leave PRS10 "as it is" or should i use heat dissipator/fan?

Cool it, otherwise it dies too soon.

A stable temperature gives better performance.

>5. Just connect the 1PPS to PRS10 1PPS input or do I have to alter 
>something on the configuration?

The PRS10 1PPS input + PLL is tricky if you want to optimize
performance, because it is not really built for that.

If you feed a GPS 1PPS directly, the "hanging bridges" causes
the PRS10 to wander.

Running the GPS through an OCXO to get (mostly) rid of the hanging
bridges and then feeding a 1PPS derived from that, is likely too
good a signal for the mediore timestamping hardware in the PRS10,
which suffers from missing codes and unlinearity.

The best solution is to feed a GPS signal directly AND feed the
"negative sawtooth correction" via the serial port.

That way the jitter on the GPS signal dithers the mediocre 1PPS
timestamping, but the serial correction prevents the "hanging
bridges" from causing wander.

Not all PRS10 firmwares support this btw.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.