[time-nuts] Cheap Rubidium

Bob Camp lists at cq.nu
Thu Dec 24 22:03:59 UTC 2009


Hi

The nice thing about a chunk of soft steel is that it also has pretty good heat capacity for a given volume of material. Kind of two birds with one stone. The only drawback I can see is that it may need de-gaussing  to get it to be reasonably stable. 

In any case, you want a full shield, a gap and then another full shield inside it. Those pesky little flux lines love to find gaps in the shield.

If you do have either one, you still have to gap it from your magnetic field generating currents. Otherwise you just make a better electromagnet. 

Bob

On Dec 24, 2009, at 4:50 PM, J. Forster wrote:

> How good are oranges compared to tanjarines? Different things.
> 
> Steel is good at high flux levels. MuMetal is good at low flux, but
> saturates and looses it's shielding capability.
> 
> In fact, plated soft steel is pretty good stuff. The tin or copper is for
> rust proofing and helps at RF because of their relatively thin skin depth.
> The plating also aids solderability.
> 
> Typically, people use a steel box on the outside with MuMetal on the
> inside...  like those Russian "nesting" dolls. ("The Tall Blond Man with
> one Black Shoe").
> 
> Also, try Googling "Netic-Conetic"
> 
> -John
> 
> ===========
> 
> 
>>> If I had a bunch of mu metal sitting in the basement I'd certainly use
>>> it in the setup. Last time I checked the stuff was not cheap ....
>> 
>> How good is mu metal relative to typical steel?
>> 
>> I'm interested in shielding/$.  If I have $X to spend on shielding (for a
>> hobby project), am I better off spending it on mu metal or junk yard
>> steel?
>> 
>> In this case, space or weight is not a significant disadvantage.  (If I
>> can
>> also use it as a thermal layer, it might even be an advantage.)
>> 
>> ------------
>> 
>> Years ago, I was helping somebody with two displays.  They were
>> interacting with each other in unpleasant ways.  We tried some thin mu
>> metal.  It didn't help much.  A big chunk of 1/8 or 1/4 steel worked much
>> better.
>> 
>> 
>> 
>> --
>> These are my opinions, not necessarily my employer's.  I hate spam.
>> 
>> 
>> 
>> 
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> 
> 
> 
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