Wanted: Comprehensive training on shielding and noise

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Billy_Bob

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Oregon
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gar

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Ann Arbor, Michigan
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EE
081005-1347 EST

Some other references stimulated by this thread:

This reference above
http://www.unitedstatesaction.com/emp_and_faraday_cages.htm
led me to
http://www.arrl.org/tis/info/pdf/88615.pdf

In general you shield electric fields from something by enclosing the something in a conductive box. At low frequencies this does not have much effect on magnetic fields. Electric fields are capacitively coupled.

You shield from magnetic fields by a magnetic material box.

Twisted wire cables are not by themselves shields but provide a means to cancel the induced voltage from a distributed magnetic field. Telephone cables and CT-5 cables use twisted pairs for this purpose.

Radiated energy is shielded by electrostatic and/or magnetic shields.

Another type of noise problem is from ground (common) paths that have an unwanted current and this current produces a voltage difference along the common path. Shielding has no effect on this type of noise.

See my web site for a discussion on noise and grounding at
http://www.beta-a2.com/noise_grnd.html

Following is an old reference with a small section on shielding:
"High-Frequency Measurements", August Hund, McGraw-Hill, 1933, p 43. I never had this book for a class, but it is interesting to look back at knowledge that had existed by this moderately early date. The superheterodyne was only a few years old at this time, and commercial radio broadcasting had only begun at the beginning of the 1920s. It is also interesting to note the very great advances from 1930 to 1940. Note that radar existed on 7 December 1941 and worked, but failure of communication because of many factors resulted in a major disaster.
From the investigation after 7 December:
http://www.ibiblio.org/pha/pha/congress/part_3.html#138
Scroll down a bit to the radar discussion.

The problem of noise in an information channel includes many factors over and above the electrical circuits.

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N

nc5p

Member
Location
Tempe, AZ
Dr. Van Doren from the University of Missouri Rolla does an excellent course. I've taken it twice. MIL-HDBK-419A is very good reference (though long) on grounding, shielding, and bonding. You can download it from several places free.
 
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