AM Broadcast RFI Kits

CABLE TV/Satellite RFI Coax Noise Filter, stops 200 KHz-30 MHz interference

CMNF-TV

CABLE TV/Satellite RFI Coax Noise Filter, stops 200 KHz-30 MHz interference CMNF-TV

CABLE TV/Satellite RFI Noise Filter for VLF, AM broadcast & shortwave from .2-30 MHz – Receive Only - F connector I/O

Purpose. The CMNF-TV is used to suppress RFI noise and interference (in the 200 KHz-30 MHz range) from common mode currents on the coaxial input line of satellite and cable TV receivers.

The filter is designed to have a high RF impedance to noise and interference from common mode currents on the outside of the coax braid while passing RF signal currents on the center conductor and inside of the coax braid to the antenna.

The effectiveness of the filter is dependent upon the amount of common mode noise encountered on the feed line. If your receive system has a large amount of common mode noise current then you should experience a reduction of common mode current which usually as heard as background noise level. Typical choking impedance is shown in the gallery picture.


The filter was quite effective. Was surprised that it actually reduced the noise level
more than the signal so S+N/N improved by 1.9 S units.

Bill
$59.95 In stock
Brand:Palomar Engineers
MPN:CMNF-TV
Country/Region of Manufacture:United States
Filter Power Rating (PEP watts):receiver only
Choking Impedance (ohms):1000 - 7000
Common Mode Attenuation (db):21 - 36 db
RFI Suppression Range (MHz):200 KHz-30 MHz
Insertion Loss (db):.02
# Ferrite Filters:3
Enclosure Size (inches):4" x 2" x 1.5"
Typical Use::Noise filter at radio end of coax next to receiver
CABLE TV/Satellite RFI Coax Noise Filter, stops 200 KHz-30 MHz interferenceCABLE TV/Satellite RFI Coax Noise Filter, stops 200 KHz-30 MHz interferenceCABLE TV/Satellite RFI Coax Noise Filter, stops 200 KHz-30 MHz interference
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 from .1 - 8.1 Mhz

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

F240-77 Choking Impedance in AM Broadcast Band

 

 

Typical Installations for Donut/Ring Toroids

AC Cable on F-240 Toroid - 6 turns

AC Cable on F-240 Toroid – 6 turns

Ethernet Cable on F-240 Toroid - 7 turns

Ethernet Cable on F-240 Toroid – 7 turns

RG58 12 turns on FT240-43 for 4000-6000 ohms choking impedance

Audio or Mic cable on F240- 12 turns

 

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