PURPOSE:The N-700 is an active electronic noise suppressor that employs a high density, low loss toroid 0.25 mH choke coupled with two power 2N3055 NPN power transistors in a capacitor multiplier configuration. The N-700 is designed to eliminate in-noise for Auto-sound Systems including: Alternator Whine, Fan Humming, ignition pops, etc.N-700 applications include Power Equalizers, Amplifiers, Cellular Phones, CB Radios, Two Way Communication Equipment, Amateur Radio Components, CD Players, and AM/FM Cassette Decks, etc.
FEATURES:The air cooled design of the N-700 filter permits maximum efficiency and effectiveness.The ferrite toroid core of the choke component of the L configuration is responsible for a very high rate of attenuation with very low line losses.The Beta of the power transistors multiples the capacitance to maximize the attenuation of the active filter. There are only three wires needed for the installation of the filter =Filter Input, Filter Output, and the Chassis Ground.The Chassis Ground is required to complete the circuit’s operation.
INSTALLATION:Make sure the noise is in-line before installing any in-line filter.A good confirmation would be to temporarily substitute a 120 VAC to a 12 VDC power supply, or a small 12 Volt motorcycle battery, for the vehicle's electrical system.If the noise goes away when the alternate power supply is connected, then you have a case of in-line noise.
To get optimum results with the N-700, the following directions should be followed:
1.Cut the component's main power lead between the fuse and the component.
2. Connect the GREEN wire to the fuse side of the cut (Source). If no fuse is present, be sure to add a fuse to this connection. Be sure to add a fuse rated at 10 Amps or less to protect the vehicle.
3.Connect the RED wire to the component side (Load). This output lead is also fused to protect the N-700.
4.Connect the BLACK wire to a good chassis ground.The N-700 will not function without a connection to chassis ground.
Practical and easy to install, the N-700 is one of the most versatile and effective filters on the market.
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 |
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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.