Re: Laptop safe for flight in planes?

[briand@aracnet.com]

>>>>> "Russell" == Russell Coker <russell@coker.com.au> writes:

  Russell> emit many frequencies.  The PCI bus has it's own frequency,
  Russell> the DRAM has it's own frequency, and whatever is done to
  Russell> convert 16V DC to 110V (*) for the back-light of the screen
  Russell> also probably causes some emissions too.

I was thinking about this and it occurs to me that such systems have
at least (marginally) passed FCC unintentional radiator specs which
puts power levels @ ~ -30dBm over all frequencies of interest, which
for a part clocked at 1-2GHz is about 5 - 10GHz (usually 5x highest
clock frequency).

A wireless card on the other hand is designed to transmit efficiently
(duh) and typical power levels are on the order of 15-20dBm.

So saying a laptop/CPU doesn't cause any problems, therefore your WLAN
card won't either is not at all valid.

Furthermore, even if you are not in the frequency band, just having a
sending a lot of power into the planes receivers could definitely
result in some level of jamming due to distortion in the front-end or
similar effects.  So the intereferer does not even need to be on
frequency to cause a problem.  Of course, this assumes poor design in
the airplanes reciever since they shold all have some substantial
bandpass filtering in the RX frequencies to keep out such unwanted
signals.


Brian