Snap On RF Choke/Isolator - 1/2"/12.7mm cable -5/10/15 Bead Option, 3-300 MHzProduct DetailsBrand: Palomar EngineersMPN: SNO-1/2-5Country/Region of Manufacture: United StatesEffective Frequency Range (MHz): 5 bead: 3-300, 10,15 bead: 1.8-300PEP Power Rating (watts): same as coax cable ratingChoking Impedance Range (ohms): 5 bead: 200-900, 10 bead: 400-1400, 15 bead: 600-1700Common Mode Attenuation (db): 5 bead: 9-20 db, 10 bead: 16-24 db, 15 bead: 17-28 dbEstimated Insertion Loss (db): .025Use 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.
Max cable size - in/mm: .5/12.7
OD (A) - in/mm: 1.22/31
ID (B) - in/mm: .514/13.1
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.
HF 1-61 MHz coax feed line common mode chokes
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.
1:1 feed line Chokes (also known as feed line current chokes, common mode chokes, line isolators, current mode chokes, and 1:1 baluns/ununs) are available in kit form or assembled form in a weatherproof Current Unun and Balun Enclosure which we call a CUBE™. All 1:1 chokes are ferrite based and are designed for 50 ohm coaxial cable input and 50 ohm output. 1:1 Ferrite toroidal or bead chokes have a higher choking impedance than our popular Sleeve Chokes and various models are available for specific frequency ranges and power levels.
1:1 Chokes are useful for choking common mode currents that may flow on the exterior of the coax cable shield while allowing the signals on the interior of the shield and the center conductor to flow unaffected and keeping the common mode current on the antenna. They isolate the coax shield and prevent it from becoming part of the antenna system.
1:1 Chokes are useful between balanced lines for center fed dipoles at their fundamental frequency (468/f (MHz), beam antennas with a 50 ohm balanced driven element, G5RV, loops, yagis, NVIS antennas, mobile installations, portable antennas and anywhere common mode current (or RFI) is a problem. They are also helpful between transmitter and linear amplifier or between linear amp and antenna tuner or as isolation chokes where higher choking impedance is needed (in the range of 2K-7K ohms).
1:1 Chokes are also very useful as feed line current chokes at the “radio end” of the antenna (we call them coax noise filters) where they choke/filter common mode current induced onto the coax shield from radiated waves (from your antenna, and other sources such as DSL routers, computer devices, plasma TVs, etc. originating in your house or your neighbor’s house). For RFI issues see RFI/EMI Solutions for general use or for specific radios and devices.
For best results we recommend a 1:1 choke at the “antenna end” of the coax and a coax noise filter at the “radio end” of the coax. (A side benefit is a reduction in noise level caused by common mode currents). 1:1 chokes are also available as Sleeve Chokes (Slip on or Snap on) for ease of installation and light weight on the antenna.