Re: NMEA ref.clock better than my ISP's timeserver?

David J Taylor wrote:
Unruh wrote:
[]
I use cat 5e cable since it is cheap, available and is supposed to be
good for better than about 100MMHz
(10nsec) signals. I would not use usb cable or any old wire, because
of
the problems of spread of the pulse from the gps. Also I would
terminate
it properly as well so that signal reflections could be problematic.
on
long runs.
If the run is less than 10m it should be ok even with improper
termination.

Cat 5e cable sounds like a good compromise. On very long runs, you would not only need to terminate the cable correctly, you would need to drive it correctly as well, requiring powered line drivers and receivers at either end.

In the OP's case, the run is only 30m (i.e. about 100-150ns) so the effect of reflections on a system (RS-232) which is bandwidth-limited to a microsecond or two should be very little, and I would likely use the cable in an unbalanced configuration.

First I don't think there's any problem getting the nmea down
twisted pair at 4800 baud.

To play safe with the ttl level pps I've setup to use a simple
emitter follower that can drive into 75r coax.

I didn't want to use line drivers as I don't have any handy that
work off single 5V supply.

I need a converter back to ttl before going to pc and don't have
any spare gates in the box with compulsory flashing led and
ticker, so will use another couple of transistors wired as
Schmitt trigger.


David
.

Relevant Pages

  • Re: Process with many NPTL threads terminates slowly on core dump signal
    ... clear false pending signal indication in core dump ... > to terminate if it receives a signal that may cause a core dump. ... > program is designed to consume infinite CPU time). ... > * The slow process termination time only occurs for those signals that ...
    (Linux-Kernel)
  • Re: Signals, threads and the use of SIGUSR1
    ... No, I think that SIGINT, SIGHUP and SIGTERM are the signals to be covered in ... >> that's OK to just terminate your process as usual, ... if you don't send explicitely SIGUSR1 to that thread upon ...
    (comp.unix.programmer)
  • Re: signals
    ... driver sends the SIGINT signal to the process attached to the terminal. ... The default action for Both SIGINT and SIGTERM is to terminate the process. ... Note that all signals but SIGKILL can be ignored or handled. ... depends actually on the signal handler installed by ...
    (comp.unix.programmer)
  • Re: threads
    ... >> POSIX thread can be terminated. ... > Yes I know that signals are delivered to all the threads and the scheduler ... The specification doesn't allow terminate, stop, continue, or ignore to ...
    (comp.unix.programmer)
  • Re: Questions about EGNOS.
    ... > I think that might be pitching it a bit strong, David. ... > that one day we will get usable signals from EGNOS, ... of the map that's at fault. ... canals etc are represented by "conventional signs" ...
    (sci.geo.satellite-nav)
Loading