Reducing AC Magnetic Fields BobÐO Schultze and Richard Perez Last issue we discussed measuring the ac magnetic fields in our home power systems. This issue we offer some solutions to the problem. These solutions are easy to do, mostly inexpensive and dramatically reduce the magnetic fields radiated by the ac wiring in our walls. The Test Setup We fed a 300 Watt incandescent heat lamp with an inverter. We wired the lamp with a variety of wiring techniques. First we used regular Romex cable with parallel conductors. Then we inserted the Romex into a 1/2 inch EMT conduit. Then we repeated the procedures with twisted pair wiring and coax, each with and without conduit. At each experimental stage we measured the ac magnetic field radiated by the wire with the milliGauss meter described in HP23. We built a cardboard jig to hold the probe exactly 1 inch from the conductors under test. This insured that all measurements were taken at the same distance from the conductor. Here's what we found out. INSERT TABLE AND CHART AC Magnetic field reduction The use of the alternative wiring techniques shown on the table can radically reduce the presence of ac magnetic fields. Twisted pair wiring inside of conduit offers the most cost-effective solution. Coax is not only expensive but also difficult to work with. Twisted pair wiring is easily accomplished by purchasing single conductor wire and twisting them together using a drill and vise. Even without the use of conduit. twisting the conductors together (about four to six twists per foot) reduces the magnetic field by over twenty times. Access BobÐO Schultze, Electron Connection, POB 203, Hornbrook, CA 96044 ¥ 916-475-3401. Richard Perez, C/O Home Power, POB 130, Hornbrook, CA 96044 ¥ 916-475-3179.