On Sat, Jan 4, 2014 at 12:05 PM, Hal Murray <hmur...@megapathdsl.net> wrote:
> > albertson.ch...@gmail.com said: > > Where those using the cat-5 wire as a twisted pair? If sothat's > "cheating" > > Yes. I was thinking that 4 pairs would be Rx, Tx, PPS, and power. If I > need > Ethernet, I'll pull another Cat-5. > Pulse quality of single-ended RS232 over unbalanced twisted pair is going to be pretty bad beyond a few feet. If you want to transport the 1pps over twisted pair there are a couple of options: 1. A BALUN. There are lots of 75ohm-to-CAT5 BALUNs out there specifically for transporting NTSC video over CAT-5. At the far end use another BALUN before running into a TTL-to-RS232 line driver. There should be sufficient drive without too much extra hardware. (Terminate into 75 ohms tho'.) 2. Use an RS-422 driver. This will accept the TTL-level 1pps in and produce a nice differential output to drive the twisted pair. You can find serial cards that have RS-422 line receivers that will plug directly into the PC. 3. Simply use coax that is properly terminated at the far end to drive a TTL-to-RS232 line driver right at the computer's RS-232 input. All three of these should result in an acceptable 1pps with jitter levels lower than the timing resolution of the NTP server you are running on the target machine. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.