This is a generic linear amplifier RFI kit for DC powered amplifiers. Works on many popular amplifiers including:
Specially designed for the Elecraft KXPA100 linear amplifier used with the KX3 and the Yaesu 817 radio (and others).
Included are the following chokes and installation guidelines:
RF Input: 1/2" Snap on – 2 turns of RG-8X size coax through center (use additional turns if using smaller cable)
RF Output: 3/4" snap on – 3-4 turns of RG-8X size cable (use additional turns if using smaller cable)1/2
Control or Relay Cable: 1/2" snap on – 2-3 turns thru center - ½” diameter hole
DC Power Line: 3/4" snap on – 2-4 turns of +/- DC cables through center
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