Max The better versions used a 2 othogonal pairs of Helmholtz coils, with the nonmagnetic shaft mounted coil rotating in the centre where the field is relatively uniform.
Braunbek coils (4 coils rather than 2) produce a more uniform field than Helmholtz coils. Braunbek coil sets are used for canceling the Earths magnetic field: http://www.iop.org/EJ/abstract/0957-0233/6/5/022 http://www.serviciencia.es/folletos/Braunbek-Barker-Examples-1.pdf http://www.igep.tu-bs.de/institut/einrichtungen/magnetsrode/index_en.htm <http://www.igep.tu-bs.de/institut/einrichtungen/magnetsrode/index_en.html>l <http://www.igep.tu-bs.de/institut/einrichtungen/magnetsrode/index_en.html> http://www.ptb.de/en/org/2/25/251/realization.pdf http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050071098_2005071182.pdf Bruce Max Robinson wrote: >>> 2. Several measurement techniques require a given phase relationship >>> (e.g., quadrature) between DUT and reference. For HF frequencies (ie, 5 >>> or 10 MHz) is there a *practical* phase shifter design covering 180+ >>> degrees that doesn't involve switching various lengths of coax in and >>> out of the line? >>> > > There was a Hewlett Packard generator called a two phase oscillator or maybe > it was two phase function generator. I forget the model number and don't > have any way to look it up. It featured two outputs and a dial calibrated > from 0 to 359 that would adjust the phase of one output with respect to the > other. Behind the panel was a little box which I didn't try to open but > the manual revealed it to have 3 coils, two at right angles to each other > and the third one on the shaft. It operated at 5 MHz. If memory serves > correctly, they called it a variable phase transformer. > > Regards. > > Max. K 4 O D S. > > Email: m...@maxsmusicplace.com > > Transistor site http://www.funwithtransistors.net > Vacuum tube site: http://www.funwithtubes.net > Music site: http://www.maxsmusicplace.com > > To subscribe to the fun with tubes group send an email to, > funwithtubes-subscr...@yahoogroups.com > > ----- Original Message ----- > From: "Joe Gwinn" <joegw...@comcast.net> > To: <time-nuts@febo.com> > Sent: Wednesday, December 24, 2008 3:52 PM > Subject: Re: [time-nuts] New topics (was Re: He is a Time-Nut > Troublemaker....) > > > >> At 5:05 PM +0000 12/23/08, time-nuts-requ...@febo.com wrote: >> >>> Date: Tue, 23 Dec 2008 11:40:51 -0500 >>> From: John Ackermann N8UR <j...@febo.com> >>> Subject: [time-nuts] New topics (was Re: He is a Time-Nut >>> Troublemaker....) >>> To: Discussion of precise time and frequency measurement >>> <time-nuts@febo.com> >>> >>> Magnus Danielson wrote: >>> >>> >>>> My intent is to get some stuff done in the lab during the vacation. >>>> (Desperatly trying to get some more on-topic discussions going). >>>> >>> Here are two questions that have been running around my head: >>> >>> [snip] >>> 2. Several measurement techniques require a given phase relationship >>> (e.g., quadrature) between DUT and reference. For HF frequencies (ie, 5 >>> or 10 MHz) is there a *practical* phase shifter design covering 180+ >>> degrees that doesn't involve switching various lengths of coax in and >>> out of the line? >>> >> Why the aversion to coax delay lines? They are simple and reliable. >> The reason will help people to tell what alternatives would be best. >> >> Joe >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.