Re: Radio in a metal cage

[dcruz@t1acc1.intel.com (Dave Cruz @ T9TO (PTL!!!))]

Being an electronics tech I'll venture on an explanation.

I think in the FM radio the receiver receives the electric field portion
of the radio (electromagnetic) wave.  That's why when you closed the
non-magnetic metal cage you put the FM radio in a Faraday shield.  You
shielded the RF section from receiving the electric field of the FM
signal.

On the AM radio:  They usually use ferite rod antennas.  The ferite rod
antenna picks up the magnetic field portion of the AM signal.  Try an iron
wire cage and the AM signal will be shielded out.

Regards,  Dave Cruz  <DCRUZ@T1ACC1.INTEL.COM>

> Last week I did this demo to my pupils: I built a non-magnetic metal cage for
> a radio. Kids loved to hear its music vanishing when I closed it. That was OK 
> for FM.
>
> Suddenly one kid asked me to try it again with AM. I thought it would make no
> difference at all, but OOPS!!!, the music did not vanished completely, and I
> could not explain the reason...
>
> Does anybody know it?
>
> PS. The cage is made of aluminium wire mesh.(aprox. 4mm side squares)