On 2012-01-09, Chris Albertson <[email protected]> wrote: >> >> >> With +/- 12VDC RS232 drivers, I've done 800' and 1000' runs >> of Cat5e @ 19.2Kbps without issues. >> >> {On the other hand, on cables designed for RS232 decades before Cat5e, >> I've had issues at one tenth that far, (~100pf to 200pf / meter) >> at 19.2Kbps. >> >> > What I may have is "self interference" of some kind. Most of the pluses > get through just fine. A few don't. Perhaps the Tx wire is close to the > PPS wire. I wonder if sending data at 9600b could effect the signal on a > parallel conductor? When I look at the logs, I see the error is almost > periodic. I've noot looked really close but the errors do seem to be > equally spaced. I saw this kind of thing once at work and it turned out > to be an air traffic control radar a couple miles away. I doubt this is > the case now but I do have ASCII in the same cable > > Your test that you can send data over cat-5 is not the same as sending two > streams of data over cat-5.
You want to make sure that your PPS pulse goes over a single twisted pair-- ie that its ground wire is in the same twisted pair as the pps signal. You would also want the tx-rx to have a different ground wire, so that the current pulse of the tx/rx does not travel down the same wire as the ground for the PPS. Of course having the signals balanced on the twisted pair would be even better. > > I'm sure I could fix this be using diferenctial drivers on a twisted pair > but I think moving the computer is the best plan. Then the PPS will be > sent over RG58 coax and level converted just inches from the computer. > > > Chris Albertson > Redondo Beach, California _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
