Snap On Split Beads

Garage Door Opener RFI Kit

In stock
Product Details
Brand: Palomar Engineers
UPC: Does Not Apply
Type: New
Country/Region of Manufacture: United States

RFI-GDO Garage Door Opener RFI Kit

This RFI-GDO kit is specifically designed to cure most garage door opener systems triggered by Radio Frequency Interference problems. The kit contains ferrite ring toroids (“Donut” shaped ferrites) for the AC power supply protection and “Snap on” ferrite beads for door sensor (2) lines and one manual on/off opener switch. The ferrites are selected to eliminate RFI from 1 to 1000 MHz. The ferrites 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, military, AM/FM and other “transmitters” (such as microwave ovens, cell phones, computers, wireless phones, HDTV systems, home automation systems/light dimmers, variable speed motors, etc) that are picked up by long wires (“antennas”) running through the house electric power wiring or device sensor wires. These “antennas” feed the interfering signals into garage door opener causing it to halt operation or act intermittently.

Note: Some of the new Garage door controls use DC motors and a Pulse Width Modulation (PWM) speed controller which can generate RFI into other electronics nearby. Use the RFI kits below to help suppress RECEIVED RFI and RFI TRANSMITTED by your garage door opener.

How to cure RFI

RFI can be stopped by suppressing the signal from the radio “transmitter” or suppressing the signal on the receiving “antenna” feeding the affected device or eliminating the RFI path between the source and victim devices. With the RFI-GDO kit, you run the wires entering the opener through ferrite cores right next to (or inside) the controller box. Ferrites do not affect the signals going through the wires but they resist the passage of common mode RFI keeping the RFI signals out of the opener and stopping the RFI from falsely triggering the opener. Some sensor lines may require multiple ferrite toroids to be most effective. Also the more turns around the toroid, the more effective the RFI filter.

Sometimes you may also have to change frequencies of your GDO to avoid interfering frequencies. Many Chamberland(Whisper Drive, etc)/Craftsman/Liftmaster GDO’s use 280-390 MHz or 315 MHz which may be be close to interfering transmitters. The RFI kit will help to suppress the interference common to all lines including AC and DC driven motors.

LED lights or LED light dimmers interfering with Garage door opener: Some brands of LED bulb circuitry operates from 30 – 300 MHz and may cause RFI to the opener. Best bet is to try different LED light brands or remove LED lights from garage and surrounding area. (read: problem is not with the LED lights but the LED circuitry within the LED bulb)

Wireless/wired Security Camera Systems can cause RFI - use the RFI-GDO kit to suppress AC induced RFI into the opener.

If the RFI is severe, you may also try placing an aluminum foil “tent” around the sides of the GDO (leaving the “front toward the door open so the antenna can still receive your remote signal).

What is included in the kit?

The RFI-GDO kit is meant to be used with a AC powered (possibly through an AC wall wart or inline dc power supply battery backup) alarm system with up to 3 input/output signal lines and a single power supply line coming into the device. Note: a standard 3 prong AC power plug will go thru the ring ferrite 3-4 times as it has an inner ID of 1.4"

TECH NOTE: We also stock RFI kits to protect effected devices such as garage door openers, computers (laptops, desktops), dsl/cable routers, ethernet hubs and many more devices. Remember there is always a “transmitter” and a “receiver” of RFI and the quest is to find and choke the “path” the RFI has selected – you need to add ferrites to both the transmitting side and the receiving side to eliminate RFI problems. The RFI kits on this page only helps suppress RFI on the receiving side.

Christmas lights or yard lights with switching DC power supplies are often the RFI source and a clamp on ferrite bead on the AC AND the DC side feeding the lights is needed to help suppress the switching power supply RFI noise.

We have also had reported wireless HDTV boxes causing RFI to garage door remote openers. Snap on ferrites on the power cord supply and/or switching the coax cable interfaces to CAT5 cable may also help solve the problem.

Obvious Tech Note: make sure your remote batteries have enough energy to activate the GDO or the signal they transmit may not be large enough to over ride the RFI signal, but a fresh battery may be able to overcome the weak RFI source and allow the GDO to operate correctly.

Save this product for later

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).


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.

Ferrite Split Beads with multiple turns of RG-58/59

FSB14 1 150x150 - Snap On Split Beads

FSB-1/4 – 1 turn

FSB 12 1 150x150 - Snap On Split Beads

FSB-1/2 1 turn

FSB12 1 Open 150x150 - Snap On Split Beads

FSB-1/2 Open Shell

FSB 12 2 150x150 - Snap On Split Beads

FSB-1/2 2 turns

FSB 12 3 150x150 - Snap On Split Beads

FSB-1/2 3 turns

FSB12 4 150x150 - Snap On Split Beads

FSB-1/2 4 turns


More examples of split bead use

20131210 1148191 300x180 - Snap On Split Beads

Ethernet Cable on FSB-1/4

20131210 114800 300x180 - Snap On Split Beads

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

Effective RFI/EMI Chokes

20131219 110956 150x150 - Snap On Split Beads

FSB-1/4 or FSB-1/2 4 turns for 14-50 Mhz 2K-3K Z

20131219 111243 150x150 - Snap On Split Beads

FSB-1/2-5 turns for 10-30 Mhz 2K-4.5K choking Z

20131219 105947 150x150 - Snap On Split Beads

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.