[ntp:questions] FreeBSD 6.2 with Spectracom 9283 GPS units?

David L. Mills mills at udel.edu
Mon Oct 29 17:46:28 UTC 2007


We have been running several Spectracom GPS and WWVB receivers here over 
the last 20 years. So far as I know, these and later receivers use the 
same suite of serial timecode formats supported by the WWVB driver. We 
use the PPS signal on the DCD line for Solaris machines and the parallel 
port for the FreeBSD machines with excellent results. The PPS signal 
from the Spectracom receivers is TTL level on BNC connectors, which are 
definitely not legacy type. The beauty of the parallel port is that it 
requires no level converter.

If you daisy chain the PPS signal to a number of machines separated by 
more than a few feet, you should terminate the last machine with a 
resister matched to the coax impedance -  50 or 75 ohms.


John Ioannidis wrote:
> I need to syncronize several FreeBSD boxes off a Spectracom NetClock 
> 9283 unit. For reasons that I can't elaborate here, I can only use the 
> RS485 and PPS signals off the 9283, not their built-in NTP servers.
> So far, it looks like my best bet is to run STP and 50Ohm coax wiring 
> from the Spectracom to the FreeBSD boxes, get RS485-RS232 converters, 
> and using some leftover BNC T connectors from the days of thinlan 
> connect the PPS signal that's coming down the coax to the signal ground 
> and DCD pins of the RS232 connector.
> Questions:
> 1. Has anyone on the list actually interfaced a 9283 to a unix box this 
> way? ANything I should watch out for?
> 2. Does there already exist a box that will do all this, so I don't have 
> to put it together myself?
> Thanks,
> /ji

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