[time-nuts] Cheap Rubidium

[Steve Rooke]

I wonder how peltier devices would work for this application. Coupled
with a temperature feedback servo they could be used to heat/cool the
rubidium. Does anyone know if they have any electromagnetic field
issues with them, the ones I have seen seem to be completely enclosed
in aluminium which should act as a Faraday cage. They have the
potential of providing a large thermal transfer capability compared
with passive devices.

73,
Steve

2009/12/25 Joe Gwinn <joegwinn at comcast.net>:
> At 10:06 PM +0000 12/23/09, time-nuts-request at febo.com wrote:
>>
>> Date: Thu, 24 Dec 2009 09:46:13 +1300
>> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>> Subject: Re: [time-nuts] Cheap Rubidium
>> To: Discussion of precise time and frequency measurement
>>        <time-nuts at febo.com>
>>
>> Joe Gwinn wrote:
>>>>
>>>>  Date: Thu, 24 Dec 2009 08:57:42 +1300
>>>>  From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>>  Subject: Re: [time-nuts] Cheap Rubidium
>>>>  To: Discussion of precise time and frequency measurement
>>
>>  >> <time-nuts at febo.com>
>>>>
>
> [snip]
>
>>>  >> 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.
>
> True enough - while there are two conductors, they are not close and
> parallel.
>
> Anyway, the point is that non-inductive components by definition have low
> magnetic fields, and that non-inductive power resistors are common.
>
> To eliminate the field from the loop of resistors, one can have a linear
> string of A-P resistors in series, with a pair of return wires in parallel,
> with the return wires on either side of the resistor string, thus reducing
> the effective loop area.
>
> Joe
>
>
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-- 
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.