[clue-tech] interesting computer case

[Nate Duehr]

Joe 'Zonker' Brockmeier wrote:
> I'd be curious to see whether most cases on the market pass that test.

Checking various cases around the house, including the laptop, most have 
a Part 15 sticker on them.  Of course, that doesn't mean they're 
RF-quiet.  My eMachines laptop throws off crap all over the UHF ham 
band.  Haven't had a chance to fire up a spectrum analyzer to see how 
bad it is, but it wipes out otherwise solid signals being received in 
certain places on the band.

> I really don't see any difference between someone using this case, (or
> workbench) and when I just put a mb on a piece of foam or a board and
> test it.

In that case, the liability for RF interference is on the person who 
fired up the PC outside of a case.  In the case of this manufacturer, 
they would be liable for any harmful interference, no matter who did it 
where, because their product ignored proper engineering practices.

> Also, does FCC part 15 apply to computer cases? It's been ages since I
> worked in radio and worried about FCC rules and regs.

I can't remember.  :-)  It just looked really really bad.

Of course, that whole "must accept harmful interference" part can be 
interesting.

The proximity-switch no-moving-parts Mac monitor buttons love UHF from 
one of my handheld radios... key the radio, down goes the box to 
sleep... key it again, it wakes up.  Found this out at a friends house 
while talking on the radio while walking in his front door... as he 
looked in bewilderment at his Mac freaking out... and that was only a 5 
watt handheld.  Would have been fun to see it super-freak with a 50w 
mobile radio stationed nearby.

Friends that do a lot of weak-signal contesting had to make sure to get 
older-style PC cases made out of steel and then ground-strap them with 
wide copper strapping to their station ground system to keep the 
computers used for logging contacts out of the super-sensitive receivers.

Seeing that the FAA is going to allow airlines in the U.S. to install 
802.11b soon (United says 2006), I think a fun new hobby will be to get 
large dishes and try to receive packets from overflying aircraft... heh. 
  The path loss at 2.4 GHz means it'll be damn near impossible at cruise 
altitudes, but anyone living near a large airport could have a lot of 
fun seeing who's aeronautical AP's they could see during the approach 
and landing phases... of course, it's likely that the toys will be 
turned off during those phases of flight too... fun to try though.

Probably get arrested thinking you're some kind of criminal/terrorist 
trying to shoot down airplanes though, but some wack job who can't tell 
an antenna from a TOW missile launcher...

It's already interesting today to listen in on ACARS data... (cockpit 
data printers airlines use to talk to dispatchers, typically).  It's all 
unencrypted, and any standard AM aircraft receiver and a sound card is 
all that's necessary.

Nate