>From my experience running a compliance facility, I'd say you are on _very_ shaky ground if you try to optimize your supply for each test. I suspect that it is clearly impractical for the device to run off of an isolated battery in normal customer operation (correct me if I'm wrong on that assumption). If I'm correct, then attempting to certify to FCC regulations with such a configuration would be clearly inadequate. From your posting, it would appear you have a significant amount of radiated frequency range common mode current flowing on the D.C. cable to the supply. This is most likely where mitigation efforts should be focused rather than "test tuning". With respect, Brent DeWitt
From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Saturday, March 13, 2004 6:22 PM To: [email protected] Cc: [email protected] Subject: Common set up for RE & CE Dear Experts, Is it necessary (compulsory) that the radiated emission test set up and conducted emission test set up should be same? My device is operating with 12 volts d.c. power and have RS485 connectivity. I used a laptop computer and a RS485 to RS232 converter to run the radiated emission pre-scan. Powering the setup (power to the device and to the RS485 to RS232 converter) with 4 different FCC / CE compliant power supplies gives different results. Laptop operated in battery mode. Frequency, at which the test fails, varies with the power supply used. So I used a 12 volts battery, fixed the issues and finished the pre-scan. For the final FCC certification can I use the battery for radiated emission testing and any one of the 4 power supplies for the conducted emission testing? Is it a rule to keep the set up common for radiated emission & conducted emission? Sincerely K.Balasubramanian Sr.Engineer, Hardware.
