RF Toroid Calculator by VK3CPU
Snap On RF Choke/Isolator - 3/8"/9mm cable, 5/10/15 Bead Option, 1-300 MHzProduct DetailsBrand: Palomar EngineersMPN: SNO-3/8-5Effective Frequency Range (MHz): 3-300PEP Power Rating (watts): same as coax cable ratingChoking Impedance Range (ohms): 5 bead: 500-100, 10 bead: 600-1800, 15 bead: 1000-2100Common Mode Attenuation (db): 5 bead: 16-22db, 10 bead: 17-25db, 15 bead: 21-27 dbEstimated Insertion Loss (db): .025Input Connector Type: noneOutput Connector Connector Type: noneGround Connector (Y/N): noneEnclosure Size (LxWxH inches): noneUse for 3/8″ Cable – RG-8X, LMR-240, etc
For 3/8” cables use five FSB31-3/8 split beads for 80-10 meters (3-30 mHz) or ten FSB-3/8 split beads for 160-10 (1.8-30 MHz) meters or use 15 FSB31-3/8 for even higher choking for 1-10 MHz.
Typical Impedance per split bead: 10 MHz: 100 ohms, 25 MHz: 163 ohms, 100 MHz: 275 ohms, 250 MHz: 275 ohm
Minimum recommended total impedance is 500 ohms at frequency of interest.
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.
Tutorials
Use for 3/8″ Cable – RG-8X, LMR-240, etc
For 3/8” cables use five FSB31-3/8 split beads for 80-10 meters (3-30 mHz) or ten FSB-3/8 split beads for 160-10 (1.8-30 MHz) meters or use 15 FSB31-3/8 for even higher choking for 1-10 MHz.
Typical Impedance per split bead: 10 MHz: 100 ohms, 25 MHz: 163 ohms, 100 MHz: 275 ohms, 250 MHz: 275 ohm
Minimum recommended total impedance is 500 ohms at frequency of interest.
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.
