tmiller11...@verizon.net said: > So does adding ~80 pF per meter or 8 nF for 100 meters (RG58) to your output > have any effect on the risetime? Because that is what it will see with an > open cable.
That way of thinking only works if the risetime is long relative to the cable length. In this context, long enough is ballpark of 4 to 10 times the prop time of the cable. For long cables, the cable initially looks like the characteristic impedance of the cable. You can see that on a scope with the classic reflection pictures. In vacuum, the speed of light is very close to 1 ft/ns. Coax varies from 60-90% of that. So if you have 10 ft of cable, it's unlikely that your driver is slow enough for the lumped capacitor approximation to be valid. With shorter cables and old gear using HC chips, you might get there. -- These are my opinions. I hate spam. _______________________________________________ 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.