Not so much design as a hobby, but my noise floor really shrunk when I powered my station with a deep cycle battery.? Wonder what the equivalent capacitance is on a group 24??? ;-)? the switching smart charger is not noticeable with the battery in line.
On Aug 11, 2023 10:50, "Reginald Beardsley via groups.io" <pulaskite@...> wrote:
Jerry,
Thanks as always. That's very helpful, though ti adds a 3rd option to test.. This seems like a good application for 1-2 Farad caps on all the DC lines adjacent to the device being powered.
That should yield sub 1 Hz RC time constants. As Ken Thompson said, "When it doubt, use brute force."
One of the things that scares me is EMI. A "make before break" relay to switch between mains supply and a battery for measurements.
At the moment I'm swamped by the consequences of a buying binge arriving.
Have Fun!
Reg
On Friday, August 11, 2023 at 11:59:02 AM CDT, Jerry <jerry@...> wrote:
This person named Adrian Rus, pretty sharp engineer and entrepreneur, (co-authored some papers with Ulrich) said (and we tested it) that you should have a minimum of 15,000uf on an individual oscillator for references. Also, and I tested this for him, we switched to lt3045 regulators as they were proven to be exceptionally low-noise and cleaned-up even dirty power supplies. We used these modules and others like them:
https://www.ebay.com/itm/274137165726?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=pX50eYVtSOq&sssrc=2047675&ssuid=UQSWHCvkTY2&widget_ver=artemis&media=COPY
For testing, I used a 60dB amp that tapped off the residual noise and A/C from the DC voltage and then fed that into my low frequency spectrum analyzer and the noise reduction was amazing.
Andrew Holme, who authored our phase noise test set, used a capacitance multiplier circuit with large caps on it. I tested it and then fed it into the lt3045s and it was pretty clean. You can stack the lt3045s for more current and also in series to reduce noise.
Big problem turned out to be shielding when testing very low PN oscillators in the -180 dBc range so for testing I switched to Dewalt 20V power tool batteries followed by the lt3045 regulators. When using batteries and 15kuf caps though, I first used the LM317 regulators and didn¡¯t see much difference but running off of mains, the lt3045s made all the difference. Every noise spike we found later was related to external energy.
If I was building a bench, I think I would have a rack of the lt3045s with a switch that fed them from batteries or from mains.
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