[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)
Am 2022-07-13 4:10, schrieb glenlist via time-nuts: Oh and now LED lights overhead your bench which are driven at 5-50kHz are are next new coupling of noise into your open bench circuits !!! The LED ringlight on my microscope creates 57KHz noise peaks when I have an unshielded low noise amplifier under it. Immediately visible on the scope, let alone the FFT-analyzer. Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)
Am 2022-07-10 9:11, schrieb Erik Kaashoek via time-nuts: @Bob, You mentioned "dual supplies with high voltage" for the first gain opamp. How much impact would dual voltage bring as its a pain to implement. I think is was Rubiola who wrote that he exploded a costly microwave mixer with a LT1028 that had lost one of its power rails. If you go AC coupling, don't forget that the input capacitor must not be selected for f-3dB but that it must be much bigger to short the thermal noise of the bias network to pV levels through the low impedance source. Otherwise you see a noise rise towards 0 Hz that is MUCH steeper than 1/f. Scott Wurzer (designer of ad797) saw that immediately on my 20 * ada4898 220pV/rtHz amplifier. Wish he was more explicit. It took me some time to get it. :-) I had 10K/100u foil, ended up with 10k/4700uF wet tantalum, which opens another can of worms. I have converted to FETs now. A few pVrtHz more, but much less noise current. In cross correlation setups, the noise current of both amplifiers produces a common voltage drop in the (common) source resistance, and that does not average away. (May apply only to voltage measurements from a single source.) Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Am 2022-06-08 21:53, schrieb Tom Van Baak: Would it be advantageous, then, to run a high-performance laboratory oscillator at its lower turnover point? Or at -78 C (CO2) or 77 K (liquid Nitrogen)? I have no idea about the crystal itself. Maybe Bernd or the SC (SantaClara) veterans can help? When I measured the Q of the recovered SC crystal from that Morion MV89A, there was not much of a difference in the wanted resonance between room temperature and +89°C. I think I have published the data here a year ago. My deep freezer in the basement can do -36°C, but the VNA is so heavy... Infineon boasted that their SIGET transistors work nicely at a few Kelvin, so it would probably not fail for semiconductor availability (BFP640 & friends). OTOH, Ulrich Rohde wrote that the noise figure of the sustaining amplifier would take a hit under large signal conditions, but I don't know hard numbers. That would not disappear. But then, in a Driscoll for example, you can give the 2 transistors enough current so they run class A and do the little bit of limiting on the output side with Schottkys. For the amplifier, that is not large signal. That might be different for an amplifier in Lee-Hajimiri style. This is Dirac pulse excitation at the peak of the cycle to avoid phase modulation, that is optimized for mixing up 1/f noise. :-) Anyway, with a noise figure of the sustaining amplifier of a dB or even a few, there is no game changer to be expected from cooling. Whispering gallery saphire, anyone? I was at the precious stones museum in Idar-Oberstein here in the 'hood and saw all these huge saphires. I left with the head full of ideas... Cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts: As far as I remember and know, you can achieve about the same phase-noise properties as you hit about the same bandwidth from the Q, and noise contribution is about the same. So, it boils down to do the supporting amplifier well. But SC can tolerate more power, so you may get more distance to the thermal noise floor. cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Turning off display on HP 58503 A or B
Am 2022-06-02 19:55, schrieb K5jv via time-nuts: On a different subject: A couple of month back I got some strong criticism about suggesting that the oven in the Z3801A was a potential source of problems. I just got another Z3801A in for repair. Same symptoms as before; appears to turn on normally but after a while goes into holdover and stay there, same LH flat lines. Once again the problem turned out to be the oven. It was unusually hot to the touch. Changing the oven solved the problem. Now my question. I have never opened one of these oven, so have no real idea exactly what is inside. I would suspect that one of the oven's thermostats is stuck in the "on" position. Since it is a "double oven", there could be two thermostats? If these are mechanical contacts, as one might expect fro the 1995 era, can they be cleaned or replaced? Comments 1965 ??? from anyone who has actually seen inside one of these ovens would be appreciated. I had a Morion MV-89A that stopped oscillating when the tune voltage was > 0.8V. I opened it and recovered the SC 5 MHz crystal. It had parameters that could be expected from such a crystal, quite good. The xtal parameters were not too different between room temperature and 85°C, stability obviously excluded. It is possible to do most development work for a new oscillator without burning one's fingers too often. There is one thermistor in the inner oven; in the outer oven there is probably sth. else, but nothing mechanical. < https://www.flickr.com/photos/137684711@N07/49585174873/in/album-72157662535945536/ > and from there to the right. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Am 2022-05-26 17:24, schrieb Richard (Rick) Karlquist via time-nuts: VNA's of any kind (no matter how small their size) don't work well on components that are too far away from 50 ohms, at least if you make a simple minded s11 smith chart measurement. There are complicated work-arounds for these measurements, but they require different configurations depending on what you are measuring, so there is no turn key or universal solution. With the low price of available VNA's, anyone can afford to buy one, but that doesn't mean they know how to use it correctly. That has been discussed extensively on the DG8SAQ vector network analyzer list on groups.io, solutions included. Now back to the repair of my 8662A! Something shorts the +20V line. That thing has much too many screws and SMC connectors. :-( And the 4274A RLC bridge is waiting with similar symptoms. That old stuff has seen its best times already. Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
Re: [time-nuts] 5.115 MHz / 10.23 MHz wanted
Am 26.02.20 um 10:24 schrieb Tom Van Baak via time-nuts: I'm pretty sure that I've seen one-off surplus 10.23 MHz or 5.115 MHz OCXO on eBay but I never thought to bid on them because the frequency was strange. If you saw one, and "bought before you thought", let me know. IIRC someone has offered a 10.23 MHz variant of the 10811 some years ago on the list. 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.
[time-nuts] Are there SC-crystals out there in the wild that are not Overtone?
I had a Morion MV89A that would stop oscillating when Vtune was more than +600 mV. So I cut it open to recover at least the crystal, for own experiments. Pics are there: < https://www.flickr.com/photos/137684711@N07/49585174873/in/album-72157662535945536/ > and then following the right arrow. To get a first impression, I soldered the crystal to an SMA plug and put it on an R ZVB-8 network analyzer and measured S11. I could see the 5 MHz resonance as a 15 dB dip. There was also a resonance at 5.45 and a smaller one another 90 KHz higher. the +10% suggest that it is an SC cut. But I could not see anything at 1 or 1. MHz, so it should be a fundamental crystal? Is that common? I made most measurements at room temperature. I can turn the hot air solder station down to 91°C which is not far away from the crystal's 87.7°C inflection point, and I could see some variation on the 5.45 MHz resonance vs. temp. I must build a fixture for the hot air because the sweep time at 1 Hz bandwidth is close to eternal. Is the un-harmonicity (???) between fundamental and overtones stronger with SC-cuts than normal AT? I also could not see anything at 15 MHz. Next I'll make a board for the PI fixture as described by Bernd Neubig in his crystal cookbook. BTW I could see some more dips with >= 10 Hz resolution. I hope that does not mean that the ZVB needs service. cheers, 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.
