On 03/03/2013 03:46 PM, Jim Lux wrote:
On 3/3/13 1:00 AM, Poul-Henning Kamp wrote:
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In message <657D7F7CC03849419A2A90752E6A60A6@pc52>, "Tom Van Baak"
writes:
When playing with watches a while ago I tried to pick up any 32
kHz signal but failed. Those with 1 Hz stepper motors were easy,
but LED or LCD displays were too electro/magnetic/acoustic quiet
for me to ever detect anything.
Most LCD and LED clocks have a shielding metal-coating on the front
glass, exactly to eliminate all EMI/EMC issues.
Yes, but perhaps there's enough leakage to make this work. After all,
the EMI requirement (assuming it's running at 32 kHz) isn't particularly
stringent and because the fob is small, the radiated field at any
distance is going to very small. OTOH, I can put a probe or coil right
on or around the fob.
I'll let you all know what I detect when I try it tomorrow.
An electrostatic shield will not contain the H-field from the shifting
currents.
Cheers,
Magnus
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