Some additional power supply notes.
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I mentioned there is a severe problem in the way most circuit designs for the uA723 have an error. I said I thought 100 ohms was needed in series with the current sense, it is 1,000 ohms. Most fried uA723 are the result of not using that 1,000 ohm resistor.
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Re noise from batteries.
Mr. Werner Ogiers is a severe audiophile. While I don't necessarily agree with severe audiophiles, I mean oxygen free cryogenically treated copper speaker cables strikes me as a bit unsane, there are some very smart and dedicated people in that clan who actually understand measurement.
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Mr. Ogiers has a series on power supplies and page 4 has noise graphs from chemical batteries.
I doubted his data and performed some tests of my own. [forget the "Some people prefer the sound of the TL431 operating in non-unity-gain" on page 3, even very smart people have their delusions.]
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I used Rod Elliot's Low Noise Test Preamplifier
at https://sound-au.com/project158.htm
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My Dataq data acquisition unit with the Low Noise Test preamplifier with SpectraPluse revealed that "Yyes chemical batteries do produce noise."
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Some batteries produce a lot of noise. And I mean A LOT of NOISE!
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https://www.tnt-audio.com/clinica/regulators_noise4_e.html
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Take it for what it's worth.
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I use Charles Wenzel's Reducing Voltage Regulator Noise
for all of my active antenna power supplies.
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For really critical, low current, needs I add a capacitor multiplier to the output. The noise is so low I can't measure it.
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Something all too many RF designers ignore is "rectifier commutation noise."
https://www.microsemi.com/document-portal/doc_view/14617-rectifier-reverse-switching-performance
[rectifier commutation noise is the term my favorite EE professor used.]
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I won't get down into the weeds over proper rectifier commutation noise snubber design but this can be a serious problem. By serious, I mean so bad as to render a very well designed linear power supply useless for RF work.
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One final note, there is no point in lowering your home grown EMI lower then the ambient RF noise floor, which, if you have AC power, telephone, cable TV, and neighbors within ~300 feet, will be rather high. Such is life and why my wife and I try to escape to a nature preserve so I can do some serious DXing.
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