Actually the purchaser does have the ability to decide on the importance of the EMI signature. Many of the laptop products only have to stand up to the A standard. Where as some companies have tougher requirements and require things to stand up to a higher standard.
I work for a company that designs bar code scanners. My company is the ONLY organization of them all in the production of large fixed installation scanners that requires our products to pass the B standards rather than class A. (Essentially the class B standards require that you are about 10dB below the class A standards). Not to mention the fact that we require that we pass with at least 3dB of margin so technically we require our products to be 13dB better than we really have to be. Not to mention the rest of the testing that we do on our products. In the large supermarket fixed installation scanners we actually slam a 30 pound bag of lead shot directly onto the scanner from 2 feet. We call this the "Turkey Drop" test. We also hit the products with 25,000 volts ESD discharges and require that this causes zero failures while the industry standard is 15KV. Anyway the point of the whole thing is that we are the manufacturer and designers of the scanner. We purchase power supplies from Chinese manufacturers and we as the purchaser mandate the requirements of the supply. If we did not there would be no way that we could stand up to our own standards. Honestly I've personally not run much in the way of testing on the laptop power supplies but I do know that we run switchers to power our products. Mainly because we need to be able to support the use of our product worldwide but also because California is now outlawing the use of unregulated transformer based linear supplies in new products. Maybe next time I'm at the lab if I have some free time I'll run some tests on my dell power supply. Honestly I have used my laptop as a host before and have found that with only some very minor mods my Latitude D610 can be made to pass class B. I only had to add a few pf's of capacitance here and there and it works great. But that doesn't mean that I don't still slap ferrites on all of the cables to and from our product that I'm allowed! :) We'll see if I end up with some free time... Although at $350 an our for lab time you tend to get very good use of the time! ;) _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
