); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] You need another independent reference oscillator for the 3325 and run the test again - that should make sure its not a synchronization idiosyncrasy.
It could be at that low of a frequency change, they are swallowing a pulse and it makes a jump.... Ulrich Bangert wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] > > Gents, > > perhaps you know that Bruce and I are working on an linear phase > comparator similar to the K34-5991A from HP (but with some features of > today) which should enable us to characterize even "better" oscillators > at an very small price. The first expriments (running since some weeks) > are very encouraging but now an problem has arised that I would like to > hear your comments to: > > For linearity tests of the circuit I need two signals that are > > a) low phase noise > > and > > b) have an very small stable frequency offset, say 0.001 to 0.005 Hz. > > The two signals that I use are > > a) 10 MHz coming from my well hung FTS-1200 + frequency doubler > > b) The SQUARE output of my HP3325A set in amplitude and dc offset so > that effectively an cmos like digital signal is generated. The HP3325 > uses the FTS-1200 as external reference. I am using this arrangement > because of the ease of offset generation as well because the linear > phase comparator currently features an well designed sine to ttl > converter only on one of its input channels, so the second channel needs > to be fed digital. > > The slow beat frequency slowly shifts the phase delay between the phase > comparator input clocks and one should get an linear output of the lpc > over time. Looked at the big scale (200 ns measurement range) the > voltage recorded at the lpc's output looks indeed picture-perfect. > > If however looked at an scale of an few ns it becomes obvious that there > is an regular sudden jump in phase of abt. 320 ps (always same > direction) every 60 seconds or so. Bruce and I have tried to remove > zillions of possible sources for that without any result. As an last > resort I made an measurment that recorded the phase comparator's output > as well as an direct time interval measurement between the positive > slopes of the input clocks and much to my surprise the jump was already > to be seen there although buried in a bit more noise due to 20 ps tic > resolution. > > I am almost sure the FTS-1200 can NOT be the source of these jumps > because it is at the same time the LO of my GPSDO system. If it were to > produce regular phase jumps (even that small) they would accumulate to > an value that would result in an noticeable reaction of the closed loop. > > Therefore the qustion: Has anyone of you an theoretical knowledge about > the HP3325 that would explain this behaviour or has anyone of you made > similar findings? In the above example the frequency had been set to > 10.000000005 Mhz, square output, 5V amplitude, 2.5V dc offset which > gives an 0 to 5 V when terminated into 50 Ohms. Can it be that the > effect is due to the sqare output? I made some tests whith seeting the > phase of the output signal which led to no noticable changes so there > could be an signifant difference of signal phase behavoiur between sine > and square generstion. > > TIA > Ulrich Bangert > > > Brooke, I hope you find my signature ok now? > > Ulrich Bangert > www.ulrich-bangert.de > Ortholzer Weg 1 > 27243 Gross Ippener > Germany > > > _______________________________________________ > 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.
