Lynn, I'm afraid you'll have to eat this one.
You use steel, iron or "Mu" metal to shield from magnetic fields.
Alu is fine for shielding electromagnetic waves (radiation), to use in waveguides, etc.
But it will NOT shield pure magnetic fields as seen from a permanent magnet or generated by an electro-magnet.
The Alu IF cans are not used to shield magnetic fields.
Maybe the confusion comes about because it's called electro-magnetic waves.
Do the test: take an oscilloscope or a TV and move a permanent magnet near the neck of the picture tube.
Repeat with an Alu plate between the magnet and the tube neck.
Repeat with an Iron (not stainless steel) plate between the magnet and the tube neck.
See the difference?
Of course I've completely forgotten what started this thread. What were we trying to shield from?
Finn
jwvoto@itlnet.net wrote:
---- Original Message ----
From: Lehanover@aol.com
To: flyrotary@lancaironline.net
Subject: [FlyRotary] Re: wire routing
Date: Sun, 4 Feb 2007 01:09:03 EST
In a message dated 2/3/2007 11:56:08 P.M. Eastern Standard Time,
jwvoto@itlnet.net writes:
Am I wrong, I believe that aluminum will not shield magnetic flux,
giving
only electrostatic shielding; only steel will shield magnetic flux.
Wendell
Notice that your IF cans have aluminum all around? Never seen an IF
can?
In the olden days radios had big vacuum tubes, and open core
capacitors to
adjust tank circuits and control frequencies. The Inter-frequency
transformers
had to be shielded to control phasing and awful noise in the output.
Thus
the aluminum can shielding. Good for wave guides as well.
Ferris metals concentrate flux fields (conduct flux lines well) and
are used
in the cores of transformers and solenoids.
Lynn E. Hanover
Why are transformers made with ferris metal? If you want to contain
all the magnetic flux, I still content that steel or mu metal is the
way to go. I have never seen an aluminum magnet.
Wendell
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