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.
I am sure you can make a case for some condition(s) where an unterminated
cable will still work. But it is not something we have been shown necessary
to make precise measurements (something this group strives for).
YMMV,
Tom
----- Original Message -----
From: "Mike S" <[email protected]>
To: <[email protected]>
Sent: Monday, September 15, 2014 10:29 AM
Subject: Re: [time-nuts] Correcting jitter on the 1
PPSsignalfromaGPSreceiver.
On 9/15/2014 10:01 AM, Tom Miller wrote:
Fast risetime pulses _are_ RF and need to be treated as such.
You say that as if simply saying it provides an explanation, or even a
reason. Exactly what ill effect on a triggered measurement is there if one
does not terminate a PPS signal properly? Does/can termination increase
the slew rate or make the speed of propagation more consistent, which
might make the measurement more accurate?
Like Tom said, what comes after the leading edge of a PPS signal (which is
the measurement trigger) seems irrelevant.
A simple though experiment. If I take a high impedance measurement at a
tap 1M from the source, and the cable ends another 100M away, how can the
termination or lack thereof at that end effect my measurement of a single
event? It's over 700 ns round trip away? If I repeat that event 1/sec, is
it any different? I can see where there would be a difference when I get
close to a 700 ns cycle time, and likely before because of "ringing." But
for a 1 second cycle? Someone will have to provide more than a dismissive
"just because" to convince me.
_______________________________________________
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.
