Hal, Your plots don't show the wave being reflected by the cable end, and bouncing back and forth.. Until settling down.
Without an end-termination the improperly terminated output of the Thunderbolt will cause the signal to bounce back and forth.. If there is a 50 ohms termination, there won't be any bounces, but a large voltage drop will happen due to the relatively high DC current over the long cable resistance.. (5V into 50 Ohms = 100mA). Maybe thats why the levels at the end are so much lower that at the source? Bye, Said Sent From iPhone On Jan 3, 2014, at 15:26, Hal Murray <[email protected]> wrote: > > [email protected] said: >> The "line driver" was a TTL inverter chip I was going through about 50 or >> 60 feet of cat-5 wire. TTL level serial is always marginal, the specs say it >> should not work but it does work most of the time. > > Modern CMOS chips work much better than real TTL. Some CMOS chips have weak > drivers. > > Cat-5 should be fine for 100 ft. > > Here are scope pictures from the PPS signal from a TBolt driving 100 feet of > various types of wire: > http://www.megapathdsl.net/~hmurray/time-nuts/coax/Coax-20ns.png > http://www.megapathdsl.net/~hmurray/time-nuts/coax/TP-20ns.png > The clump on the left of each graph is the input. The stuff on the right is > the output. The scatter is due to the different prop times. > > > > -- > These are my opinions. I hate spam. > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
