The Thunderbolt's output impedance on the PPS output is much less than 50 ohms, more like 5 ohms.
If you terminate the other end of the cable with a good 50 ohms termination, you will be OK, even though it would be better to put a ~47 ohms series resistor right at the TB output before driving the cable. This will reduce the available amplitude, but will reduce ringing even more. Check this page: http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.html I used the PPS output of the Thunderbolt as a fast rise time pulse generator for cable matching/reflections experiments. It will show you what to expect when you use that output to drive a long cable. Didier KO4BB > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Dave Brown > Sent: Wednesday, March 26, 2008 2:57 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Buffering the 1pps output from a Z3801A > > Peter > All comments so far relate only to the Z3801A. The Trimble > Thunderbolt has a TTL level 1 pps 10 uSec pulse output on a > BNC connector intended to be loaded with 50 ohms. AFAIK > there is no ECL level pps output available from the > Thunderbolt via its 9 pin serial port connector. > It's cetainly not mentioned in the Thunderbolt documentation if it is. > > DaveB, NZ > > ----- Original Message ----- > From: "Peter Vince" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Thursday, March 27, 2008 2:29 AM > Subject: [time-nuts] Buffering the 1pps output from a Z3801A > > > > Bruce, et al, > > > > The 1pps output of an HP Z3801A and Trimble Thunderbolt is > > only available (as far as I know) as a balanced ECL signal on the > > 25-pin connector, with dire warnings in the manuals about not > > earthing either side of the ECL signals. Would you be able to > > advise > > on a simple buffer circuit that would allow me to drive the usual > > unbalanced 50-ohm coax please? > > > > Thanks, > > > > Peter Vince (London, England) > > > > _______________________________________________ > > 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. > > > > > > -- > > No virus found in this incoming message. > > Checked by AVG. > > Version: 7.5.519 / Virus Database: 269.22.0/1342 - Release Date: > > 25/03/2008 10:26 > > > > > > > _______________________________________________ > 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. > > No virus found in this incoming message. > Checked by AVG. > Version: 7.5.519 / Virus Database: 269.21.8/1339 - Release > Date: 3/22/2008 4:43 PM > > No virus found in this outgoing message. Checked by AVG. Version: 7.5.519 / Virus Database: 269.21.8/1339 - Release Date: 3/22/2008 4:43 PM _______________________________________________ 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.
