Re: [time-nuts] Building a DMTD/phase noise set in the 21st century
I've only used an ultra low esr 33F supercap made in Korea in the source circuit of the input JFET on a preamp. Down to 10Hz at least it didn't appear to add significant noise to the 4nV/rtHz @10Hz preamp. Bruce > On 26 August 2019 at 13:52 Didier Juges wrote: > > > How do SuperCaps compare with electrolytics noise-wise? > > Didier KO4BB > > On Sun, Aug 25, 2019, 9:04 AM Gerhard Hoffmann wrote: > > > > > Yes, these electrolytic capacitors can produce ugly effects. > > > > The winner is clearly the cheap > > > > < https://www.digikey.de/products/de?keywords=1189-1056-ND > > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building a DMTD/phase noise set in the 21st century
How do SuperCaps compare with electrolytics noise-wise? Didier KO4BB On Sun, Aug 25, 2019, 9:04 AM Gerhard Hoffmann wrote: > > Yes, these electrolytic capacitors can produce ugly effects. > > The winner is clearly the cheap > > < https://www.digikey.de/products/de?keywords=1189-1056-ND > > > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building a DMTD/phase noise set in the 21st century
Am 25.08.19 um 10:52 schrieb Hal Murray: att...@kinali.ch said: As you have always two channels, I would recommend to use two mixers fed with an LO that is 90°C out of phase to get I and Q components. How does that compare with running a single channel twice as fast? At low enough frequencies, the two ways are identical in performance and linked by the Hilbert transform. At high enough frequencies, ADC performance starts to suffer. One gets a smaller "effective number of bits" ENOB as sample rate and/or input frequency rise. In that region one may gain an advantage by halving the sample rate at the cost of doubling the hardware and needing a Hilbert transformer, also known as a wideband 90° phase shifter. The phase shift might come cheap, depending on the upstream processing. One could also time-interleave 2 ADCs or even more. Some ADC chips do that internally, and some scopes, too. regards, Gerhard. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building a DMTD/phase noise set in the 21st century
Am 24.08.19 um 23:49 schrieb Jan-Derk Bakker: there may be some flicker noise present, I've not personally seen the poor DC performance in many S/D audio converters either (apart as artefacts from the front-end electrolytic coupling capacitors). Yes, these electrolytic capacitors can produce ugly effects. purple = DigiKey 493-4582-1-ND organic polymer Alus 4700u/2.5V blue = Digikey 1189-2962-ND 2200u/25V green = DigiKey 1189-1056-ND 3300u/10V Rubycon, cheap The winner is clearly the cheap < https://www.digikey.de/products/de?keywords=1189-1056-ND > The test circuit is an Interfet IF3602 based low noise baseband amplifier. I definitely wanted no bias loop via the gate and also for some reasons no feedback into the source, so I enforced the drain current with a current mirror. That is ugly, because the source must be AC-grounded with huge electrolytics. In the test setup, there were 4 in parallel. There is only 500 mV across the capacitors. Even the 2V5 organic polymer is not challenged voltage-wise. The traces are the own input voltage noise of the amplifier. The horizontal part of the traces is about 250 pV/rtHz noise density. The bad capacitors both show a 1/f**3 rise, in textbook quality. At 1Hz is the lower passband corner of the following stages. I wonder what process produces that. Generation/recombination and most others do only 1/f**2. A 4700u/25V wet slug tantal showed no weakness. But at $100 a pop I like to avoid them. Vishay costs even 3 dB more than AVX. :-( regards, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building a DMTD/phase noise set in the 21st century (was: Keysight N5511A - phase noise measurements down to theoretical-177 dBm/Hz)
att...@kinali.ch said: > As you have always two channels, I would recommend to use two mixers fed with > an LO that is 90°C out of phase to get I and Q components. How does that compare with running a single channel twice as fast? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Building a DMTD/phase noise set in the 21st century
Attila, How would you rate the HP E1437A VXI ADC for this application? ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
