Use for 1/2″ Cable – RG8, RG213, LMR-400, etc.
For 1/2” cables use five split beads for 80-10 meters (3-30 MHz) or ten split beads for 160-10 (1.8-30 MHz) meters or use 15 for even higher choking for 1-10 MHz. For 144 MHz use only 4 beads as they will provide > 500 ohms. Typical common mode suppression is -9 to 30 dB depending upon the number of beads and frequency. Quite often 20 dB is considered the minimum effective reduction.
Typical Impedance per split bead: 10 MHz: 90 ohms, 25 MHz: 156 ohms, 100 MHz: 250 ohms, 250 MHz: 305 ohms
A minimum impedance of 500 ohms is needed for 50 ohm cable or 10 times the cable impedance for other cables to make a measurable difference in common mode current suppression.
The beads clamp to the cable and may be operated as is for indoor use. However, it is strongly suggested that they be covered to protect the plastic covers from weathering – use electrical tape for best results or heat shrink to ensure longer life. All kits come with instruction manual which covers assembly and application tips.
As you can see from the impedance vs frequency graph, you can very effectively increase the choking impedance by increasing the number of beads on the cable.
Snap On and Slip on Feed line chokes available in sizes to fix cables with outside diameters of 1/4", 3/8", 1/2", 3/4", 1" - check website for other size options.
tech note: For RFI frequencies below 3.75 MHz, choose SNO75-1/2-5, 10 or 15 for improved common mode rejection
Note: Ferrite beads may be hexagonal or square shape depending on inventory on hand at time of order.
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.
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