[ntp:questions] Use of GPSD and redundant 1 PPS sources (mobile comm center)

Danny Mayer mayer at ntp.org
Sun Nov 22 05:54:02 UTC 2009


John,

Noone else seems to have responded to this. The best person to answer
these questions is Dave Mills who developed ntpd. Since he's a professor
at the University of Delaware he's very close to you!

I have copied him on this response as he may not have seen it.

Danny

John K. Scoggin wrote:
> 
> Hello all. I am building a stratum 1 timing source as part of my
Mobile Communications Unit 37 project  here in Delaware.Â
> 
> 
> 
> I have mounted a Garmin GPS18 LVCÂ receiver on the vehicle's roof
along with building the 1 PPS level converter as described in this web
page  and providing TOD and PPS to an NTP standard in a small (1RU)
Intel server under Fedora Core 11 which I plan to use with LinuxPPS . Â
I have three questions for the experienced time keepers on this list:
> 
> 
> 
> 1. It would be advantageous to me if I could share access to this
> GPS
among several other applications along with NTPD. Does the GPSD daemon
introduce any serious issues with regard to reasonably accurate
timekeeping?
> 
> 2. Is there a graphical monitor available for the vehicle's network
operator to observe proper operation of this system, including the
status of the satellite constellation visible at the time?
> 
> 3. I also have an HP Z3801 GPS-disciplined oscillator and a
Symmetricom RubiSource 2000 on-board to provide a stable 10 MHz clock, 1
PPS, and an AMI-formatted T-1 clock for my on-board telephone switch and
satcomm equipment. Has anyone in the group built a device to
automagically utilize the 2nd 1 PPS signal in the event that GPS is
obsured or unreliable?
> 
> 
> 
> Many thanks and 73s, 
> 
> john 
> 
> 
> 
> Charter Member of Geeks Ubiquitus 
> 
> _____________________________________ 
> 
> 
> John K Scoggin, Jr. W3JKS/AAT3BF/AAM3EDE/AAA9SL 
> 
> US Army Military Affiliate Radio System 
> 
> Delaware Gateway Station AAB3DE 
> 
> Special Consultant - Technology 
> 
> Emergency Operations Officer – Delaware 
> 
> “Old RADEF Officers never die, they simply decay exponentially…” 
> 
> 
> 
> Chief Engineer 
> 
> Mobile Communications Unit 37 (AAT3CAD/W3MCU) 
> 
> http://www.armymars.net/ArmyMARS/MCU/index.html 
> 
> 
> ARRL Assistant Section Manager – Delaware 
> 
> Email: aat3bf at armymars.net 
> 
> Telephone: (302) 451-5000 
> 
> 
> Â  
> 
> 
> john 

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