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.
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
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
Typical Installations for Donut/Ring Toroids
 AC Cable on F-240 Toroid – 6 turns |
 Ethernet Cable on F-240 Toroid – 7 turns |
 Audio or Mic cable on F240- 12 turns |
Extra Mix 75 Snap On Beads HERE – VERY effective for AM Broadcast RFI