Hi, Paul. Glad to see you made it here. For the time-nuts; Paul and I have spoken about these issues, and I have had similar experience. The only thing I would add is the the spikes to seem to occur less frequently with a better antenna placement, but when they start to cluster, they fire off one every two or three seconds, sometimes faster.
JimT On Wed, Feb 27, 2013 at 2:08 PM, Paul Berger <phb....@gmail.com> wrote: > > Hello all: > > I am an electronic technician with 30+ years experience fixing > computers. In my spare time I like to play with old computers and > electronics. Recently I got bit by the precision timing bug, partially > after running across the wonderful leapsecond.com site, which lead me > here. First I got a FE-5680A, then after reading some of the archives > here I bought a Nortel / Trimble 45000 GPSDO and still later a used > Thunderbolt-E. > > My main interest in these devices at this time is for a accurate bench > top frequency source, however I do have a 59309A running off of each of > the GPSDOs. I am wondering if they will drift apart, but I suspect I > will need to wait a long time to see evidence of that. I set them > simultaneously by setting them both to the same GPIB address and > connecting them to the same bus on my HP-86B, this works well for > setting them but I have to remember to disconnect one or change the > address on one before I try to read them. > > MY question concerns the thunderbolt-E, I have been using LH to monitor > both of the GPSDOs and was quite surprised to see that the Nortel 45000 > seems to perform much better than the thunderbolt-E, I thought that the > E being a newer device it would perform better. I will admit that I > have a much less than ideal antenna setup however the antenna location > is the same for both devices, they are only a couple feet apart. The > antenna's are a Trimble magnet mount antenna and a the dome antenna that > came with the thunderbolt-E kit. Initially I had the magnet mount > attached to the Nortel and the dome antenna attached to the E, but I > have now swapped antennas but it has not made any difference , and I am > beginning to wonder if my E is in fact defective. I have been in > contact with one other person who has an E and his experiences have been > similar to mine, even though he has a much better antenna setup, so I > would like to ask if there is anyone else out there with an E, and ask > the group for comments on what I am seeing. > > My observations have been that the 10MHz is not very stable, on LH I > will see relatively large spikes in the DAC voltage that of course > impacts the 10MHZ, I had it connected to my 5316A counter that was > running with the FE-5680A as a timebase, with a 10 second gate time and > logging counts with my 86B and I was seeing excursions og over 100Hz > which I guess percentage wise is not huge but I do not see anything like > that on the Nortel. Now some of these excursions do occur when there > are satellite switches, and if they all occurred coincident to satellite > switches I would mark it up to my crummy antenna arrangement, but they > don't they occur even when the satellite tracking is stable and often > come in groups of several transition first positive followed by an equal > transition in the negative direction. There is also a constant > chatter of about 100uV on the DAC line as reported by LH which also > translates to noise on the OSC and PPS lines, my technician sense thinks > that looks like power supply noise, but I have not looked under the hood > yet. One really annoying thing I have noticed is the E reports having > saved my location, however it apparently has not so every time it resets > for whatever reason it goes into a self survey, which because of my less > than ideal antenna setup usually takes some time to complete, even a > warm reset resulted in it losing it location and entering self survey. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
