Unruh said the following on 05/29/2008 05:00 PM: >> <shameless_plug> >> If you need to distribute the same PPS signal to a number of boxes, I >> designed a board which is being sold as a kit by TAPR (we have >> arrangements with someone who can assemble them for a fee, if required) >> that provides up to six TTL level PPS signals, as well as two RS-232 >> compatible signals. Check http://www.tapr.org/kits_tadd-3.html. >> </shameless_plug> > > Why BNC connectors?
Because most time-and-frequency related test gear uses coaxial cable for interconnects, and BNCs are the most commonly used connectors. For really precise measurements, connectors that are threaded rather than pressure-fit, like SMA or TNC, are preferred. But the BNC is pretty universally used. The TADD-3 does have two RS-232 level outputs on headers that mate with ribbon cable to DB-9 adapters, but the performance (specifically, the pulse rise and fall times) is much worse than the TTL levels because the RS-232 spec calls for relatively slow transitions to minimize RFI. We use the fastest version of the MAX-232 level converter chips, but it's still orders of magnitude slower than the rise-time of the coaxial outputs (which are a couple of nanoseconds). John _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
