AM Broadcast RFI Kits

Coax Common Mode Noise Filter - 500 Watts PEP, 100 KHz-30 MHz LF & BCB up to -46db Noise Reduction

SKU CMNF-500-50LF
$69.95
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Coax Common Mode Noise Filter - 500 Watts PEP, 100 KHz-30 MHz LF & BCB up to -46db Noise Reduction
Product Details
MPN: CMNF-500-50LF
Country/Region of Manufacture: United States
Filter Power Rating (PEP watts): 500
Choking Impedance (ohms): 1K-14K
Common Mode Attenuation (db): 21-46 db
RFI Suppression Range (MHz): .1-30
Insertion Loss (db): .025
# Ferrite Filters: 1
Enclosure Size (inches): 3" x 2 x 1"
Typical Use:: Coax Noise filter at radio end of coax

For coax feed lines with receive and transmit signals, you will love the small size, wide frequency range and excellent attenuation of common mode noise interference emphasizing low frequency range of 100 KHz to 10 MHz but working well up to 30 MHz.

- Reduces broadband common mode receiver noise* picked up on the outside of the antenna coax feed line.

- Low frequency range works on all brands of radios and coax fed antennas

- Common mode noise rejection up to -46 DB (3-8 "S" units) depending on frequency

- Simple plug & play installation: plug a short jumper from the CMNF-500-50LF to your radio and plug the feed line into the other SO-239 CMNF-500-50LF input. Either connector can be input or output. Rated at 500 watts PEP, 50 ohm input/output

- will work with Bias-T antenna switches and will pass DC voltage from input to output with no attenuation

* not effective for noise from AC power lines or noise received directly by antenna

Installation Note: For best results, and to reduce co-interference between choked and unchoked coax feed lines with multiple antennas, ALL antenna feed lines entering the radio room need to have a separate feed line choke particularly if they are at a different frequency then HF, like VHF or UHF.

If you use a antenna switch for multiple antennas in the 1-61 MHz range, place the CMNF-500-50LF in the "common" line of the antenna coax switch and the receiver or for better isolation, place one filter in each antenna line to isolate the multiple coax braids from one another..

Got Common Mode Noise? Not Sure - Find out now by clicking link below:

Palomar Engineers Common Mode Noise on Coax User Diagnosis Test

If you use a higher powered transceiver over 500 watts PEP or use an amplifier, consider the CMNF-1500HF (1.5KW PEP) or CMNF-5000HF (5KW PEP) placed at the output of the amplifier.

See related products for coax jumpers or double male barrel connector for direct connection to radio.



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