[time-nuts] New topics (was Re: He is a Time-Nut Troublemaker....)

[Bruce Griffiths]

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: max at maxsmusicplace.com
>
> Transistor site http://www.funwithtransistors.net
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> Music site: http://www.maxsmusicplace.com
>
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>
> ----- Original Message ----- 
> From: "Joe Gwinn" <joegwinn at comcast.net>
> To: <time-nuts at 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-request at febo.com wrote:
>>     
>>> Date: Tue, 23 Dec 2008 11:40:51 -0500
>>> From: John Ackermann N8UR <jra at 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 at 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
>>
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>>     
>
>
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