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.
Generator RFI testimonial:
Bob Received your order in a timely fashion. Tried the generator kit on Sunday & it drops the noise from S9 to S5 and took out all the electrical noise. I may want some more toroids from you at some point for other interference problems I have here. Ken VE3KCY
Using an amplifier? Don’t forget our Linear Amplifier RFI Kits
Want to make up your own RFI kits for a particular operation? Here are links to some of typical RFI solutions used in portable operations:
If you use a computer for logging in your portable operations, RFI getting into computers will often lock up your computer and/or radio and a computer RFI suppression kits may be helpful
Make your expedition or portable operation a pleasant and fun outing and remember to take along your RFI kits so you have more time to operate rather then to troubleshoot intermittent or noisy receiver conditions.
Portable Antenna Kits
If you need an effective portable antenna which folds up for transport yet is easy to deploy at your operating site, consider the BULLET series of end fed wire antennas.
BULLET Antennas (click on link or picture for more info)
