BASIC Desktop Computer RFI Kit - AC Powered
This RFI kit is specifically selected to suppress most household computer device RFI problems. It contains a large ferrite ring for AC power supply protection and Snap On ferrite split bead filters selected to eliminate RFI from 1 to 300 MHz. The beads are easy to use, don’t require modification of the protected equipment and work in almost all cases, even when plug-in filters fail.
The RFI-Desktop kit is meant to be used with a AC powered computer (desktop type) with up to 6 input/output signal lines and an AC power cord line coming into the device. Included are one large ferrite ring filter and six, 3/8” inner diameter snap on split ferrite bead filters for the input/output lines.
Installation is easy. AC power cord through ring filter multiple times and snap on filters on I/O cables nearest computer - problem cured!
For additional devices like a printer and AC powered speakers, consider the Deluxe Desktop RFI Kit with additional filters.
AM broadcast transmits on a low frequency with large antennas. Consequently it takes a large antenna to receive the signals. Typical “antennas” are AC house wiring, phone lines, long satellite or cable TV cables, DSL/CAT5 lines running between rooms, etc. The device wires that connect to these “antennas” need to be choked with as many turns through the ferrite as possible. Some installation examples are shown below on this page.
For AC/ DC power cords and coax cables the F240-77 (2.4″ OD, 1.4″ ID) “Donut” toroid is the most popular. Also available are smaller toroid donuts and Mix 77 beads. Shown below is a graph with 8, 10, and 12 turns through the toroid – obviously more turns has higher choking impedance. Mix 77 toroid products are HERE and Mix 77 small beads (for small wires) are HERE
F240-77 Turns Comparison from .1 – 8.1 Mhz
Shown below is a graph of frequency response verses choking magnitude for a F240-77 in the AM Broadcast band for a 12 turn coil around the toroid. (Same info as above but different frequency range).
F240-77 Choking Impedance in AM Broadcast Band
Typical Installations for Donut/Ring Toroids
 AC Cable on F-240 Toroid – 6 turns |
 Ethernet Cable on F-240 Toroid – 7 turns |
 Audio or Mic cable on F240- 12 turns |
Extra Mix 75 Snap On Beads HERE – VERY effective for AM Broadcast RFI