Computer Radio Frequency Interference Kits
RFI-DIGITAL – for Digital Audio/PSK31/FT8, etc.
These RFI kits are specifically selected to cure most household computer device RFI problems. It contains Snap On ferrite split beads selected to eliminate RFI from 1 to 300 MHz. The beads are easy to use, don’t require modification of the protected equipment and work in almost all cases.
What causes RFI? Strong signals from nearby amateur radio, CB, AM/FM broadcast stations and other “transmitters” (such as microwave ovens, cell phones, desktop, laptop, and tablet computers, wireless phones, baby monitors, fish tank heaters/pumps, etc) that are picked up by long wires (“antennas”) running through the house including electric power wiring, telephone cables. alarm system wires, speaker wires, whose signal may be coupled into the computer connected to the digital interface with your radio causing intermittent operation.
How to cure RFI – RFI can be stopped by suppressing the signal from the radio “transmitter” or suppressing the signal on the “antenna” feeding the affected device.
With the RFI-DIGITAL kit, you run the wires entering the device through ferrite cores right next to the interface. Ferrites do not affect the signals going through the wires but they resist the passage of RF keeping the RF out of the appliance and stopping the RFI.What is included in the kit?
The RFI kit is meant to be used with a DIGITAL interface between your computer and the radio. These digital interfaces consist of sound cards, or Signalink type devices using USB or serial cables interfaced to the computer and a RADIO cable to the radio or driven device.
Installation
The 3/8” snap on is used on the USB/Serial cable between the interface and the computer. Use 1 snap on at the device end of the cable and another at the computer end of the cable and wrap 2 or more turns thru the center of the core and snap shut. Two 3/8" snap-ons included.
Similarly, use the ½” diameter snap on beads for the RADIO cable between the device and the radio. Two 1/2" snap-ons included.
Use two or more turns thru the snap on ferrite and use one at the device and another on the end of the cable near the radio. If your interface device uses a DC supply you can wrap the DC supply cable in the ½” ferrite with the radio cable. Use at least 2 turns for best results.A completed installation will look like the picture below (remember to add similar ferrites at the radio end of the cable).