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Re: No UPS's - Re: [linrad] Buying the Linux PC for Linrad use.

Dave, you seem to have good working knowledge of the different FCC certifications when it comes to computer, etc. Maybe you could give the group a very brief run-down of the standards and how they affect us.

Someone else on the list mentioned only using dc-dc supplies as a strategy to avoid generating RFI. I don't understand this idea. Isn't a dc-dc supply simply a switcher? Seems to me the operation is not much different from the line operated computer supply. A poorly designed switching power supply generates RF noise and it doesn't matter where the primary power source comes from--line operated or battery.


At 04:15 PM 7/5/03 -0500, you wrote:

I want to offer the group a piece of advice when considering
putting an Pc system together or adding to - that is a UPS.

During the certification (of our rolling around the hospital
product) I ruefully discovered that the PC's built in UPS
supply was extremely noisy - conducted emissions wise.
Finding this surprise required additional testing and defining
a new device operation mode:  "power off - ATX supply
in standby."

The UPS part of the PC supply actually runs all of the time,
in effect it's a power conditioner which runs 100% of the time.

Note, if you are considering an external UPS supply - they
may also operate all of the time as "power conditioners."
The switching power supplies in these things are very  noisy!

The manufacture of these devices are claiming compliance
(to the FCC's old definition of a Class A digital device for
radiated emissions,)  that the "USER must accept interference
from the operation of it."  (This is my pharaphasing of the FCC

If you want to buy a UPS - ask for a "money back guarantee"
given the possible of radiated emission interference.  Some
manufacturers are stating their UPS's are Class B compliant,
try them first - but make sure there exists a money back guarantee
in case it "self jams you."  Good luck & 73's

dave garnier - wb9own