AM Broadcast RFI Kits

Coax Jumper Choke - LMR-400 - RFI Range: 3-65 MHz, -25 dB Common Mode Noise Reduction, 5 KW PEP

SKU JC-1-5000
$59.95
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Coax Jumper Choke - LMR-400 - RFI Range: 3-65 MHz, -25 dB Common Mode Noise Reduction, 5 KW PEP
Product Details
MPN: JC-1-5000
Country/Region of Manufacture: USA

Simple Hi Power Jumper Feed Line Choke

The simplest, most cost effective feed line choke is a ferrite ring installed as shown in the picture (at the antenna feed point) to stop feed line radiation or at the radio end of the coax to suppress common mode coax noise current on the coax braid.

Improves antenna pattern by preventing your dipole from becoming a tripole

Suppresses pesky coax braid radiation and RFI

Reduces coax braid common mode current up to -25 dB ( 4 "S" units) on receive

Use one choke for each antenna feed line

Add a double female barrel connector to act as an "extension" of the existing coax.

UHF (PL-259) Connectors on each end

DIY with your own coax with a FSB31-1-1 ferrite snap on (1-300 MHZ)


When considering solutions for AM broadcast (550 Khz – 1.8 Mhz) you should consider Mix 77 ferrites available in a variety of shapes and sizes.  Choose a size to give the maximum number of turns of the affected wire or cable.

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 1024x648 - AM Broadcast RFI Kits

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).

AM Band Choking Graph F240 77 1024x648 - AM Broadcast RFI Kits

F240-77 Choking Impedance in AM Broadcast Band

 

 

Typical Installations for Donut/Ring Toroids

20131210 114716 150x150 - AM Broadcast RFI Kits

AC Cable on F-240 Toroid – 6 turns

20131210 115137 150x150 - AM Broadcast RFI Kits

Ethernet Cable on F-240 Toroid – 7 turns

20131222 125533 150x150 - AM Broadcast RFI Kits

Audio or Mic cable on F240- 12 turns

 

 Extra Mix 75 Snap On Beads  HERE – VERY effective for AM Broadcast RFI