Simple AC Power Cord Noise Filter Choke+ Power Cord included
The simplest, most cost effective AC power cord noise filter is a ferrite ring installed as shown in the picture (at the appliance AC input) to stop feed line appliance radiation back into the AC power line or into the radio/appliance to suppress common mode power line noise current on the AC power cord or to suppress common mode noise present on the power lines from degrading the performance of the attached device.
Keeps RFI out of appliances like TV, radios, computers, etc and like wise keeps noise generated by electronic devices from feeding the noise back into the AC power line and affecting other devices plugged into the same lines.
These chokes are cheap, easy solution for RFI issues. Just replace your existing power cord with these pre-wound cables and enjoy interference free operation.
Got your own AC power cable that needs a ferrite ring only? The use ACCF-1.4 ring. This ring also works well on switching power supplies (use 1 on AC input and another on the DC output or just order kit RFI-SMPS).
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