[time-nuts] webcam app to watch for and time stamp changes

[Magnus Danielson]

On 03/03/2013 03:46 PM, Jim Lux wrote:
> On 3/3/13 1:00 AM, Poul-Henning Kamp wrote:
>> Content-Type: text/plain; charset=ISO-8859-1
>> --------
>> In message <657D7F7CC03849419A2A90752E6A60A6 at 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