[time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron

[Taka Kamiya]

I am experimenting with exactly the same thing.  PRS-10 with Thunderbolt.  

PRS-10 takes about a day to stabilize.  When physics lock happens, it has limited stability - which is mentioned in manual.  Before I calibrated, I waited for 2 days.  These movements are visible if you feed GPSDO into channel 1 of scope and set a trigger on it, and feed PRS-10 output to channel 2.
For thunderbolt GPSDO, I am using a telecom unit, Nortel GPSTM modified with 1 pps output.  PRS-10 can take this input and lock, but it takes 1 to 2  hours to lock up.  I've tried 3 different GPSDO and they were all the same.  When it locks on, it is still not stable.
Why?  Because nature of GPSDO and Rb, time constant is set to 2 to 3 hours.  (still experimenting)  It takes few cycles of this to lock and stabilize.  In short, you'll be safe if you wait 24 to 48 hours.  Rb modules are relatively cheap.  I really don't see a need to baby it.

--------------------------------------- 
(Mr.) Taka Kamiya
I'm stuck in a wormhole....  Hello, worms! 

    On Friday, March 8, 2019, 4:00:34 AM EST, Forrest Christian (List Account) <lists at packetflux.com> wrote:  
 
 Hopefully you'll all grace me with a few answers to a beginner
time-nut question or two.

I have a PRS-10 I've never used other than to power it on with a
recently-acquired heatsink and verify that it seems to operate
correctly and that the operational parameters don't seem out of
tolerance.  I would like to use this in the near future as a 10Mhz
reference for a TAPR TICC which I'd like to use to measure the jitter
performance of the PPS output of various consumer GPS receivers, the
goal being to end up with a jitter histogram.

So three interrelated questions:

1) Assuming the PRS-10 has been off for a long time, how long should I
plan on leaving this on for the 10Mhz to stabilize?  I see the
longest warmup time on the spec-sheet is 7 minutes -  although this
seems a lot shorter than I'd likely use in real life,  I'm also not
sure if there's much benefit to an excessively longer warmup time
(like days), would like opinions on this.

2)  Longer-term I'd like to use the 1PPS output from a Trimble
Thunderbolt to calibrate the PRS10 and adjust if necessary just to
trim out any aging drift on the PRS10.  Initially I thought I was
going to discipline the PRS10 on a continual basis with the
Thunderbolt using the PPS input on the PRS10, but I've recently
realized that leaving the PRS10 on permanently might not be the best
option (see Question 3).  So I'm looking for opinions on how to keep
the PRS10 calibrated/adjusted.  I.E. trim with the trimmer, adjust
using digital commands, etc.

3) As implied in #2, I was originally planning on leaving the PRS10 on
a continuous basis.  I've read a couple of things which imply that
there is little benefit to doing so, and that every hour it's on
consumes the lamp life.  Assuming I only need the highly stable PRS10
source every few months for things like jitter measurements on 1PPS
sources, is there any benefit to leaving the PRS10 on?

-- 
- Forrest

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