Hi I’ve played with both the 6 db loss resistive splitters and the transformer based 3 db loss splitters. They both seem to be fine for splitting precision 10 MHz signals. For a while I avoided the transformer based parts, but not for any reason I could prove.
Bob On Mar 10, 2014, at 7:41 AM, Volker Esper <[email protected]> wrote: > Even if the -3dB were an issue, I'd have much more faith in a clear, passive > resistor network than in a complex amplifier with all it's unknown non linear > characteristics, temperature dependent time delays, noise sources, etc., etc. > This simple home made network is a useful, manageable gadget. > Volker > >> Bob Camp <[email protected]> hat am 10. März 2014 um 01:47 geschrieben: >> >> >> Hi >> >> So far, I have not found the 3db lost in a a passive splitter to be a problem >> with anything I have played with. With proper termination , they seem to be a >> good thing to use. >> >> Bob >> >> On Mar 9, 2014, at 7:55 PM, Volker Esper <[email protected]> wrote: >> >>> Bob, >>> >>> I sometimes indeed do arc welding, as well as forging... But that's >>> another story. >>> >>> When waiting for an ADEV measurement I sit still, trying not to move a >>> millimeter. Seriously, I try to avoid any rf noise, e.g. ham radio, any >>> airflow, any temperature change. I log supply voltages and check, if >>> there's anything odd. I avoid any switching supply. I regularely check, >>> if any switching voltage regulator (TV, monitors, PC,...) disturbs my rf >>> ether... >>> >>> As the legends of my plots tell, I do use a passive splitter to get two >>> similar signals (start and stop) for phase measurement. But I haven't >>> used it for splitting the 10MHz for frequency measurement (reference and >>> input). >>> >>> Lower level is a concern, since it increases phase jitter. >>> >>> Volker >>> >>> >>> Am 09.03.2014 23:32, schrieb Bob Camp: >>>> Hi >>>> >>>> Do you routinely do arc welding while waiting for an ADEV plot to finish >>>> :)… (I drink beer, but not everybody is into that …) >>>> >>>> You might consider trying a passive splitter on one of the outputs of the >>>> GPSDO. There aren’t many ways they will mess up a signal other than by >>>> dropping it’s level. If level is a concern then indeed they could be an >>>> issue. >>>> >>>> Bob >>>> >>>> On Mar 9, 2014, at 6:17 PM, Magnus Danielson <[email protected]> >>>> wrote: >>>> >>>>> On 09/03/14 22:36, Volker Esper wrote: >>>>>> Am 09.03.2014 19:46, schrieb Magnus Danielson: >>>>>>> On 04/03/14 01:05, Volker Esper wrote: >>>>>>>> Am 03.03.2014 23:04, schrieb Magnus Danielson: >>>>>>>>> Volker, >>>>>>>>> >>>>>>>>> On 03/03/14 00:50, Volker Esper wrote: >>>>>>>>>> Sorry for the "time delay"... >>>>>>>>>> >>>>>>>>>> TIC: SR620 with Z3805 as external reference; signal source >>>>>>>>>> Nortel/Trimble GPSTM (GPSDO) 10MHz output >>>>>>>>>> >>>>>>>>>> Enclosed two plots (SW: "Plotter"): >>>>>>>>>> - one is sigma(tau) calculated from phase samples (SR620 TIME mode), >>>>>>>>>> - the other one is sigma(tau) from frequency data (SR620 FREQ mode) >>>>>>>>>> >>>>>>>>>> Whole equipment had a power up time of several days/weeks. Room >>>>>>>>>> temperature was stable over both measurements (within about 2 degrees >>>>>>>>>> C). >>>>>>>>> The SR620 uses a bit different path through the logic when doing TI >>>>>>>>> and FREQ measurements. The frequency measurement has a "feature" that >>>>>>>>> means that the time error between start and stop signal needs to be >>>>>>>>> calibrated out. This can be done using the calibration routines given >>>>>>>>> in the manual. This should not affect the ADEV measure, but as a >>>>>>>>> precaution. >>>>>>>>> >>>>>>>>> Try doing a pair of noise-floor measurements. That is, feed the >>>>>>>>> reference 10 MHz to the A input for the frequency noise measurement. >>>>>>>>> Then, for the TI noise-floor measurement, put a T on the A input, put >>>>>>>>> it in high-Z mode and then use a 1 m cable to put the signal onto the >>>>>>>>> B input which is terminating. >>>>>>>>> >>>>>>>>> You indeed have a higher level. Your initial shape makes me wonder. I >>>>>>>>> would really like to get the TimeLab measurement files and eye-ball >>>>>>>>> them closer. >>>>>>>>> >>>>>>>>> If you plot the phase or frequency, it may be easier to spot >>>>>>>>> systematic wobbles. TDEV would also help, as it provides a general >>>>>>>>> *tau scaling to the ADEV plot. >>>>>>>>> >>>>>>>>> Cheers, >>>>>>>>> Magnus >>>>>>>>> _______________________________________________ >>>>>>>>> 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. >>>>>>>> I already did these measurements, I stick the plots at this posting. >>>>>>>> >>>>>>>> - The plot with the long file name shows frequency mode measurement: >>>>>>>> 10MHz external reference put into channel A. >>>>>>>> - "...Plot2" shows a phase measurement, where I fed the reference >>>>>>>> signal >>>>>>>> via a home made 50 ohms splitter into both input channels. (I prefer >>>>>>>> feeding the channels symmetrically) >>>>>>>> Both plots show linear negative gradients, but the phase plot is >>>>>>>> steeper. The frequency plot transitions into a horizontal at about >>>>>>>> 1000s. >>>>>>> The 1/sqrt(tau) curve is higher than the background noise of the >>>>>>> counter. That flicker phase noise is more typical of a buffer or >>>>>>> source than of the counter. >>>>>>> >>>>>>> For shorter taus I would expect the white noise to dominate. >>>>>>> >>>>>>> I'm just surprised about the level of flicker phase noise. What is the >>>>>>> source? >>>>>>> >>>>>>> Cheers, >>>>>>> Magnus >>>>>>> _______________________________________________ >>>>>>> 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. >>>>>> Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional >>>>>> buffer, however, the Z3805 has two (buffered) outputs. I used one for >>>>>> counter reference, the other one for counter input. >>>>> Hmm... what is the noise when you measure it on the SR620 itself? >>>>> >>>>> It seems a little high here. >>>>> >>>>> Cheers, >>>>> Magnus >>>>> >>>>> _______________________________________________ >>>>> 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. >>> >>> _______________________________________________ >>> 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. > _______________________________________________ > 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.
