It's a compromise. NiCds are quiet, but they have to be recharged and can have high self-discharge rates and grow whiskers internally.
If I were building a one-off or a few amps, and Hg batteries were plentiful in the stockroom, I might well use them also. In the PAR 113 the NiCd pack has to be replaced pretty often. The unit is either in battery charge or operate mode. They do not 'float charge'. If you get them used, the battery was not even wirth testing. Digi-Key would make up replacements for $100-$150, but that was a while ago. I don't know if you can noise model a battery as an ideal voltage source in series w/ a Thevenin Equivalent, and use the Thevenin resistance in SQR(4KTBR), but it seems at least plausible. This would explain why bigger batteries reported;y have lower noise, at least in part. -John ================ > A long time ago, when I was concerned about a phase noise issue, I found > an > old NBS article. It was on measuring phase noise and included a schematic > of > an ultra-low noise amplifier. In that amplifier they used Mercury > batteries. > I also glanced at the referenced article, stating NiCad is the lowest > noise, > and, NiCads were available for a long time, yet they used Mercury. > Regards > - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of David Kirkby > Sent: Thursday, July 11, 2013 10:25 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Lead acid battery noise levels > > On 11 July 2013 05:47, Mark Spencer <[email protected]> wrote: >> Eric: >> >> http://tf.nist.gov/general/pdf/1133.pdf >> >> discusses the noise levels of various batteries. >> >> Regards >> Mark S > > > Sod's Law comes into play here. From a quick read of that, it seems NiCd > are > best, but they are being phased out. I was told they were banned in > Europe, > but I don't know if that is true. I'm pretty sure I've seen NiCd tools in > the local DIY store, so I doubt it is true. > > Dave > _______________________________________________ > time-nuts mailing list -- [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
