Wall Wart RFI Noise Filter


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Product Details
Country/Region of Manufacture: USA

PURPOSE:The N-25 is a passive noise suppressor that employs a high density, low loss toroid 0.25mH choke designed to eliminate in-line noise for Auto-sound, Avionics, and ham radio/CB/Two-Way communication systems including: Alternator Whine, Fan Hums, Dodge Ram Cummings Torque Converter Clutch Cycling Repair*, etc.The N-25 applications include Power Equalizers, Small Amplifiers, Cellular Phones, CB Radios, Two Way Communication Equipment, CD Players, and AM/FM Cassette Decks, etc.

FEATURES:The air-cooled design of the N-25 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.There are only three wires needed for the installation of the passive filter -Filter Input, Filter Output, and the Chassis Ground.

INSTALLATION:Make sure the noise is in-line before installing an in-line filter such as the N-25.A good confirmation would be to temporarily substitute a 120 VAC to a 12 VDC power supply, or a 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-25, 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. (If there is no fuse, add one --- 10 Amps is recommended)

3.Connect the fused Red wire to the component side.

4.Connect the Black wire to a good chassis ground.

Practical and easy to install, the N-25 is one of the most versatile and effective filters on the market.

Note: The 30-Amp rating is instantaneous = peak… not constant. Fuse the Green lead with a 5 to 10-Amp fuse. Average current draw should be no larger than the fuse size of 10 amps.

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Wall Wart switching DC power supplies that plug into the AC power line plug and provide DC power to laptops, routers, battery chargers, cell phone chargers, etc are a known source of broadband RFI (a.k.a dirty electricity) that effects many electrical devices including computers, radio receivers, HDTV systems, etc.  In many cases this extra RFI noise effects computer I/O speeds since they have to error correct the information packets many more times due to the noise interference causing packet errors.  A ferrite ring can often increase data throughput by reducing the error correction to normal rates.

A simple ferrite ring filter on the DC power line can help suppress the RFI noise affecting the victim device or keep the DC power cord from acting as an antenna and radiating RFI into other victim devices. This kit is also useful on laptop computer supplies, routers, cable modems, wireless phone charges, etc.

RFI WW Installation 300x288 - Wall Wart RFI Noise Filter

Installation is quick and easy: Just wrap the DC power cord through the center of the ring filter as many times as you can and reinstall.  For best results with long DC power lines, use one at the ring filter at the wall wart end (to prevent the wall wart power supply from using the DC line as an antenna) and another at the DC plug end (to prevent the electronics in the powered device from using the DC power cord as an antenna).  Typical installation is shown below:

The filter suppresses RFI in from .1-100 MHz.   Inside diameter is 3/4 inch/19 mm.

Since most households and office environments have multiple wall warts we offer the Wall Wart RFI Filter kit in bulk quantity packages.

Known RFI Generators include Roku/Sling-TV power adapter - Interference heard in the AM broadcast band
 and harmonics.
Also many ethernet Cable/DSL modems, cell phone chargers, computer power adapters have the same issue:
using the AC or DC side of the power supply as a radiating antenna.

RFI solution is to use a linear power supply, change adapters or wall wart ferrite filters