Hi If that's what they are doing, it's going to have a lot more mag field than a twisted pair winding. I already know that twisted pair has enough field to make trouble ....
Bob On Dec 23, 2009, at 3:46 PM, Bruce Griffiths wrote: > Joe Gwinn wrote: >>> Date: Thu, 24 Dec 2009 08:57:42 +1300 >>> From: Bruce Griffiths <[email protected]> >>> Subject: Re: [time-nuts] Cheap Rubidium >>> To: Discussion of precise time and frequency measurement >>> <[email protected]> >>> >>> Bob Camp wrote: >>>> Hi >>>> >>>> So if I want to set up 4 uncorrelated systems, that would require 20 tons >>>> of >>>> water split into 4 tubs. Each tub would be roughly 3' x 4' x 15'. Of course >>> > if they are all in the same basement, I still have a correlation problem. >>> > My >>>> guess is that no matter what I do, any system that controls all the systems >>>> the same way will run into correlation. >>>> >>>> Oils, silicon fluids, and the like mostly hold less heat than water so the >>>> tubs would get bigger. Maybe a few tons of mercury... >>> Try about 145 tons of mercury per rubidium source as the specific heat >>> of mercury is about 1/29 that of water. >>> The redeeeming feature is that it will only occupy about 2.14x the volume. >>> The specific of some oils may be as large as 1/2 that of water however >>> the density is around 10-20% lower. >>> >>>> Active heat control and a rational heat sink is sounding like a better >>>> approach... >>>> >>> Distributed heating using wire wound or printed heaters perhaps, but to >>> reduce the associated magnetic field bifilar winding should be considered. >> >> Non-inductive power resistors, which are commercially available, have very >> low magnetic fields. >> >> The low-inductance resistors have Ayrton-Perry windings, which are bifilar. > No, Ayrton-Perry windings arent bifilar. > Classically a flattened helical winding was made on a insulating card. > An identical winding was then wound in the opposite direction on top of the > first winding and the 2 were connected in parallel. > The idea being that the small magnetic field produced by one flattened helix > is cancelled by that of the other flattened helix. >> >> <http://www.token.com.tw/resistor-pd/power-resistor-ah.htm> >> >> >>> The major limitation is that the 25W or so dissipated by the rubidium >>> source has to be transferred to ambient without raising the rubidium >>> temperature too much. >>> This limits the maximum thermal resistance between the baseplate and >>> ambient that can be safely used. >> >> I would be tempted to regulate temperature by actively controlling the speed >> of the fan (or pump) driving air (or oil) through the heat sink, as has been >> suggested. >> >> Joe Gwinn > Bruce > > > _______________________________________________ > 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.
