Hi Yup, welcome to the online auction lottery ….. As you may have noted, I’m struggling a bit with the Phase Station and random (likely my fault) issues.
At the same time, I’m going around in circles about the R&S FPC-COM2. It’s a pile of money, but it would replace a lot of questionable gear I have sitting here. Most of what I have was quite literally pulled from / saved from the dumpster at various points over the last few decades ….. Bob > On Feb 24, 2020, at 12:33 PM, Taka Kamiya via time-nuts > <[email protected]> wrote: > > I woke up this morning, check my HP105B, it's absolutely going nuts. Heater > temp down, frequency ALL OVER the place. No output in any of the ports. > Sigh..... eBay strikes again! > > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Sunday, February 23, 2020, 7:52:02 PM EST, Bob kb8tq via time-nuts > <[email protected]> wrote: > > Hi > > Ok, but thats “high pass in the RF section”. You really do not have an audio > high pass > filter the way you would in a more typical DMTD. > > If it’s any comfort, I’m sitting here looking at a very different box. It > also has “wobbles” > as you get into parts in 10^-16. That might change a bit if the draft coming > through the > window was a bit less. > > Bob > >> On Feb 23, 2020, at 6:12 PM, Jan-Derk Bakker <[email protected]> wrote: >> >> Dear Bob, >> >> The capacitors are 47n NP0/C0G types (Kemet C0805C473K3GAC7800), picked for >> low tempco (and low DF and other non-ideal behavior). I've not spotted any >> hysteresis artefacts in these in previous designs, but I haven't measured >> their performance in this circuit. >> >> Forgot to mention in the previous message: the baluns are transformers >> (M/A-COM MABAES0060), so the only DC the ADC should see is its own input >> offset (plus offset current across the 25R input filter resistors). Full >> schematic is here ( http://www.lartmaker.nl/time-nuts/DMTD_rev0.99.pdf >> <http://www.lartmaker.nl/time-nuts/DMTD_rev0.99.pdf> ; needs cleanup, but >> all connections are there). >> >> JDB. >> >> On Sun, Feb 23, 2020 at 10:13 PM Bob kb8tq <[email protected] >> <mailto:[email protected]>> wrote: >> Hi >> >> What does the temperature coefficient of your “hardware HPF” filter caps >> look like? >> Are they a type that has significant hysteresis? >> >> Bob >> >>> On Feb 23, 2020, at 3:05 PM, Jan-Derk Bakker via time-nuts >>> <[email protected] <mailto:[email protected]>> wrote: >>> >>> Dear Attila, >>> >>> Thanks for the heads up. >>> >>> I am currently using a HPF both in hardware (capacitive coupling into the >>> balun driving the ADC inputs) and in software before the ZCD. This should >>> counteract the first-order effects of this offset, although second-order >>> effects (converter nonlinearity et al) will of course still be an issue. >>> The plots you've quoted include (different kinds of) DC offset correction >>> for all but the "unfiltered" data; getting an efficient DC offset >>> correction working in real time on this 8-bit platform was indeed one of >>> the main challenges of the software-only approach. >>> >>> The FPGA daughterboard is currently in production at Eurocircuits; I hope >>> to have time to work on those the coming month. I'll also try to book some >>> time in our climate chamber. (I've had one of our GPSDO-designs running in >>> our general labs since before Christmas; surrounding it with bottles of >>> water works well enough to low pass filter temperature swings, but I still >>> see 6 degrees C swings overnight as out HVAC only runs during business >>> hours.) >>> >>> To be continued, >>> >>> JDB. >>> >>> On Sun, Feb 23, 2020 at 8:11 PM Attila Kinali via time-nuts < >>> [email protected] <mailto:[email protected]>> wrote: >>> >>>> Good evening! >>>> >>>> I'm going through some old stuff... >>>> >>>> >>>> On Wed, 27 Nov 2019 00:29:19 +0100 >>>> Jan-Derk Bakker <[email protected] <mailto:[email protected]>> wrote: >>>> >>>>> This has yielded a combined "simple" signal >>>>> processing path of a differentiator, a double comb filter and the offset >>>>> estimator, which is getting very close in performance to the "ideal" band >>>>> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the >>>> BPF; >>>>> full plot: >>>>> >>>> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf >>>> >>>> <http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf> >>>>> for this 600000-second recording: >>>>> >>>> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png >>>> >>>> <http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png> >>>>> . OADEV past ~1000sec is severely compromised by the fact that the >>>>> measurement setup is in my home lab which sees temperature swings of up >>>> to >>>>> 20 degrees C and which does get bumped from time to time. Longer runs in >>>> a >>>>> more controlled setting forthcoming). >>>> >>>> >>>> I can offer an explanation for the large effect of the zero correction seen >>>> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp >>>> setting). >>>> Converted into phase error due to zero crossing shift, this turns into >>>> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and >>>> per channel, which means, it could very well be that the channels are >>>> not matched in their temperature characteristics and thus the total phase >>>> shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is >>>> more likely. >>>> >>>> Summa sumarum: DC offset correction is important if a zero crossing >>>> detector is used. >>>> >>>> Attila Kinali >>>> >>>> -- >>>> <JaberWorky> The bad part of Zurich is where the degenerates >>>> throw DARK chocolate at you. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> <mailto:[email protected]> >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> <http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com> >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> <mailto:[email protected]> >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> <http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com> >>> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
