CMNF-5000HF for transmitter/receiver coax lines up to 5000 watts PEP - 1.8-60 MHz!
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
- Reduces broadband common mode receiver noise* picked up on the outside of the antenna coax feed line.
- Wide frequency range works on all brands of radios and coax fed antennas from 1.8-60 MHz
- Common mode noise rejection up to 15-38 DB (2-5 "S" units) depending on frequency
- Simple plug & play installation: plug a short jumper from the CMNF-5000HF to your amplifier output and plug the feed line (or a jumper to your antenna tuner) into the other SO-239 CMNF-5000HF input. Either connector can be input or output. Rated at 5000 watts PEP.
- 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 1.8-61 MHz range, place the CMNF-5000HF in the "common" line of the antenna coax switch and the antenna tuner/amplifier.
For additional common mode noise reduction, consider the CMNF-500HF (500 watts PEP) placed between the receiver and the amplifier.
Got Common Mode Noise? Not Sure - Find out now by clicking link below:
Often it is difficult to slip beads on a cable because of a plug or connector. Split beads solve this problem. They come in two halves that fit over the cable. A plastic snap cover holds the two halves together and holds the assembly on the cable.
For RFI use, mix 31 is effective from 1-300 Mhz, mix 43 works from 20-250 Mhz, Mix 61 is for 200-2000 Mhz, and mix 77 favors .1-20 MHz. These frequencies are those of the interfering signal to be eliminated, not the operating frequencies of the equipment to be protected.
Not sure of what sizes you need or solving a RFI problem with devices using multiple size cables? Try the Ferrite Snap On Combo Pack which has sizes from 1/4″ to 3/4″ with either Mix 31 (1-300 MHz) or Mix 61 (200-2000 MHz) or Mix 75 (150 KHz – 10 MHz).
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Bead dimensions are shown in the picture below and in the table as A, B, C
Ferrite Split Bead Dimensions
Application Notes
Application Note for using these Snap On split beads: How Many Chokes do I need?
You can very effectively increase the choking impedance of smaller cable by using a large hole ferrite bead and wrapping the cable through several times. For particularly difficult common mode current/RFI problems you may need a choking impedance as high as 5-10K ohms. Using multiple beads and multiple turns through each bead will give higher impedances up to a point. At higher frequencies, when the number of turns approaches an electrical wavelength, the choke becomes resonant due to stray capacitance and the inductance of the cable and limits the high end impedance values to less than the above table points.
Some example of ways to wrap cable are shown below.
 FSB-1/4 – 1 turn |
 FSB-1/2 1 turn |
 FSB-1/2 Open Shell |
 FSB-1/2 2 turns |
 FSB-1/2 3 turns |
 FSB-1/2 4 turns |
—–//—–
More examples of split bead use
Ethernet Cable on FSB-1/4
Ethernet Cable on FSB-1/2 – 3 turns for 9X Impedance good filter for 15-30 mhz between 2K-3K ohms choking Z
Three Effective Radio Interference Filters
 FSB-1/4 or FSB-1/2 4 turns for 14-50 Mhz 2K-3K Z |
 FSB-1/2-5 turns for 10-30 Mhz 2K-4.5K choking Z |
 FT240-43 – 14 turns for 3-14 Mhz or use two FT240-43 for 1.8-10 Mhz |
These snap-on chokes are useful for reducing RFI in public address system amplifiers, speaker wires, mic cables, mixer panels, coax cable, telephone wires, computer sound card speakers, dsl/cable connections, remote control heads for ham transceivers (Especially FT-100, FT900, IC-706, IC-7000), AC power cables, DC power cables, home theater cables, video cables, HI Fi cables, guitar amps, linear amp cables, etc.
They are also helpful in suppressing common mode noise/RFI in radio and TV receivers, audio and RF amplifiers. They can also help suppress noise generated by treadmills, exercise equipment, fish tank heaters, oil heater pumps, fluorescent lights, motors, cable modems, DSL modems, computers, and many other electrical devices. Common mode current reduction in computer cables often helps speed up computers.