Hi Dana, I will look closer at the 1 PPS. I found I had the scope setup wrong and the 1 PPS is 3.84V when terminated in 50 Ohms. And about 5V with overshoot when terminates in a higher impedance. I will take some measurements and determine the output impedance of the GPSDO 1PPS and design a suitable pad. Since the pods of the 5372A are always terminated in 50 Ohms the risk of damage is much less.
I will also look at how HP did the 2.5:1 attenuator in the pod. It might be a good place to start on an external attenuator design. Thanks for suggestions. Dave VE7HR Sent from my iPhone > On Jul 2, 2020, at 10:53 AM, Dana Whitlow <[email protected]> wrote: > > I like Bob's suggestion about using an L-pad. Even if the line driver *is* > happy driving > 50 ohm line (which I was admittedly assuming), the L-pad approach will keep > the > driver cooler which will likely reduce warmup drift of its propagation > delay as well as > extend its lifetime. > > Dana > > >> On Thu, Jul 2, 2020 at 9:20 AM Bob kb8tq <[email protected]> wrote: >> >> Hi >> >> Probably the easiest approach is an L pad at the input to the measurement >> device. >> Something like a 470 ohm in series and a 120 ohm to ground. A 50 ohm pad >> may not make the line driver in the source device very happy …. >> >> Something more exotic would be to do a distribution amp. Use a NC7SZ125 at >> the >> input so it’s 5V tolerant. Run however many of them you need to drive the >> desired >> number of outputs. Power it all off of 2V and you have 2V p-p output(s). >> >> Keep in mind that 2V p-p “logic” signals may or may not trigger CMOS level >> stuff >> powered off of 3.3V. CMOS running on 5V gets into the “not going to >> happen” >> area. >> >> Bob >> >> >> >>>> On Jul 1, 2020, at 9:37 PM, VE7HR <[email protected]> wrote: >>> >>> Are there any suggested method to reduce your 1 PPS signal to a safe >> level for your test equipment? >>> It seems like my HP Z8316A is outputting slightly more than 5V into 50 >> Ohms. >>> >>> Up till now I have been using a 10 MHz output from the Z3816A. But I >> understand 1PPS is a better signal to put to Channel A. >>> >>> My HP 5372A seems to default to 2V Max level if you hit instrument >> default. I am starting to like it so I don’t want to trash an input >> module. >>> >>> I think I might try a TICC in the near future but for now I will have to >> slum with the vintage HP iron. >>> >>> Thanks >>> Dave >>> VE7HR >>> >>> Sent from my iPhone >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
