ANTENTOP- 01- 2016 # 020

Experimenters with Non Snap Ferrite Cylinder Bead RF Chokes

By: Igor Grigorov, VA3ZNW,

Richmond Hill, Canada

Recently there are lots devices that contained some RF sensitive or vice versa RF generation parts inside. It is power AC/DC converters (aka power supply), Computers, Computer Monitors, et cetera. Most common way to radiate unwanted interferences or receipt unwanted interferences is cables going apart those above mention parts. It is possible to kill the effect by RF- Chokes that installed on the cable.

There are two common types of RF Chokes. First, most simple is a ferrite "bead" choke, consisting of a cylinder of ferrite encircling to the cable. Figure 1 shows that RF Choke installed at the end of cable going from a Power Supply. It is fixed non demountable choke. You cannot move the choke around the cable the ferrite cylinder may be removed only by destroying that device. Second one is a snap RF Choke. Figure 2 shows the choke. The choke may be easy moved along the cable and if it is needed may easy removed from the cable.

 However, recently life time of those devices is limited. As usual it is limited by entering of new technology to our life. So, old, but still good electronic equipment, for example, CRT TV and monitors, video and audio tape recorders and et cetera go to scrap. Some new made devices as well go of operation and became ready for scrap. At this case it would be wise to remove all RF Chokes from the device for using them in ham radio purposes. It is very easy to remove the Snap RF Ferrite Choke from the device. I usually keep the chokes on the coaxial cable going from my transceiver IC-718 to SWR- meter (and then to the antenna). The chokes reduce electrical noise and unwanted RF current induced to the outer side of the shield of the coaxial cable. Figure 3 shows cable going from transceiver to the SWR meter with Snap RF Chokes on it. As well the Snap RF Chokes always are behind me that means I should newer lost it in my de-e-ep junk box.

Figure 1 Ferrite "Bead" Choke

Figure 2 Snap Ferrite Choke

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