h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hello all. I have switching power supplies I use on heavy truck applications. The supplies basically take 12 volts @ 6 amps and convert it to 2.5 volts @ 22 amps. Problem here is that there is EMI from these power supplies are affecting a small percentage of the trucks CB radios. Literally causing so much static that range and transmissions are very short on distance. I have tried noise suppressors and filters. They do achieve the goal to eliminate the EMI, however the range suffers. I have also tried using EMI filtering adhesive tape between the stainless steel cover and the stainless steel cabinet. Still nothing.

Any input on the issue would greatly be appreciated.

Switching power supplies are the bane of my life. They usually switch at quite low frequencies which means filters are large and expensive, especially at higher currents. But as your interference is RF you might be OK with cheap ones.

The tape wouldn't work because the interference is conducted. It'll happily propagate down all the low-impedance copper wire and throughout the vehicle electrics, and can then radiate from any point. You need a filter in the 12V input line, as close to the power supply as possible. You can then seal the "gap" with tape.

Search www.rswww.co.uk, and try a few cheap filters. Obviously it'll have to be capable of taking 6A and provide good attentuation at CB frequencies.