[time-nuts] 1PPS questions

[Dana Whitlow]

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 <kb8tq at n1k.org> 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 <ve7hr at ve7hr.ca> 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
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