At 07:51 PM 1/8/01 -0500, Arnold G. Reinhold wrote:
>>all, fluorescent bulbs don't leak much intelligence :-) but they
>>sure cause electrical noise.
>You may be right about their concern being to prevent interference 
>with their listening equipment, but I don't agree with your last 
>point.  As I understand it, all electrical wiring coming out of a 
>TEMPEST enclosure has to be carefully (and expensively) filtered. 
>The power wiring to lighting fixtures can pick up and re-radiate 
>compromising signals.


 By shielding the fixtures, they effectively 
>place the lights outside of the enclosure.  

Yes.  But 1. you'd still want a filter the power mains
inside your physically secured zone 2. The site had a 
generator... and presumably a guarded perimeter (think 
1/R^2) so emissions were probably less important than
listening sensitivity...

I'll bet the wiring to 
>those fixtures is within carefully grounded conduit.

Building codes often require this, anyway, though probably
not grounded to the extent of someone concerned with emissions.
Again, it makes much more sense (cost, number of items to check
periodically) to put isolation centrally.  

>It would be fun to take a tour!

It looks like those RF astronomers would be willing, if you
shut your cell phone off while visiting :-), though likely
miffed that you're more interested in the facility than in the


Another possibility is that they were so freaked by the static sensitivity
of early MOS devices that they grounded the carpets...



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