Snap On RF Choke/Isolator - 1/4"/6mm cable, RG-58/59/06/LMR240 - 3-300 MHz, -5/10/15 Bead Option
Quantity | Price per item | Discount |
2 items | $14.95 | 12% off |
10 items | $12.95 | 24% off |
Use for 1/4″ Cable – RG-58, RG59, RG-6, LMR-240, etc
For 1/4” cables use five FSB31-1/4 split beads for 80-10 meters (3-30 mHz) or ten FSB31-1/4 split beads for 160-10 (1.8-30 MHz) meters or use 15 FSB31-1/4 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
Select 10 bead version for 160 meter use. 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.
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.
Great
ASAlton S.Verified buyerInstalled on LMR-240 feeding a dipole, no RF back into the shack A+
MTMark T.Verified buyerReasonable price for 15 of these and I didn’t to rummage through a dirty junk box at a hamfest to get them. I shrink-wrapped 7 just below where the feedline attaches to my antenna. The order comes packaged with a good information sheet. Easy to understand.
DBDaryl B.Verified buyerEasy installation
DTDanny T.Verified buyerThese Snap-On Ferrites have high quality cases that carefully align and lock together the two halves of the Ferrite material. Applied to your Coax in a 5-10 Count series, they create a "Maxwell" type of Common Mode Current "Choke" that impedes Common Mode Current from passing down the outside of your coax. This type of Choke forces the Common Mode Current to go to the antenna elements instead of traveling to the grounded point of your radio because the path to the antenna has less impedance than going down the outside of the coax. This accomplishes two objectives - 1) Reduces the RF "Noise" that hits your antenna and/or the outer shield of your coax and prevents it from coming down your coax shield and getting to the radio, 2) Increases the Impedance (resistance) around the outside of your Coax Shield and significantly minimizes the amount of RF Current that can travel down the outside of your Coax Shield as Common Mode Current (makes it radiate off of your antenna instead if applied at your antenna's feed point). I used a series of 7 of these 1/4" ID Type 31 Snap-On Ferrites snapped around the two foot long ABR240 Coax jumper at the feed point connection to 10M Wire J-Pole antennas (which are actually End Fed Half-Wave design antennas) to work as a Common Mode Current "Choke". Common Mode Current is a design issue with all End-Fed Half-Wave Antennas and a "Choke" like this prevents it from coming down the outside Shield of the Coax and makes it radiate from the Antenna's radiating element instead. The Snap-On Ferrites are a great product that I highly recommend be applied to every End Fed Half-Wave Antenna. 73, Bob
RBRobert B.Verified buyer
What are the resistive and reactance components? (5 and 10 beads)
see graph