Ferrite beads prevent electromagnetic interference emi in two directions.
Ferrite core cable modem.
Choosing the wrong type of core will affect its performance too if any.
There s a large am radio station transmitting near you swamping the front end of your modem.
I simply slapped a split core ferrite onto the telephone cable near the rj 11 jack going into my dsl modem and another one on the cat5e cable just before the rj 45 jack into the nic and the speed shot up.
I ve 2 of these rj 45 ethernet cables but each cable only has 1 x ferret choke on 1 end of the rj 45 so.
I think my speedstream 5242e dsl modem itself was the cause of alot the rfi noise as my cable are pretty short and are all under 3ft.
Modems already have ferrite beads inside.
Ferrite cable cores are available at mouser electronics.
I fitted a couple of ferrites clip on maplin jobs to the power cable to my router not the phone network cable.
Mouser offers inventory pricing datasheets for ferrite cable cores.
The magnetic field is absorbed by the ferrite core and which converts magnetic energy in to heat energy.
This video just hits a generic use at a high level.
Depending on the size of your cable the larger inner diameter toroid may be the most effective.
Now consider a cable passes through the ferrite core and which carries both noise signal and data signal.
I moved one ferrite choke core to the ethernet cable and left.
I move the two ferrite choke cores to the dsl modem power cord.
Adsl runs at around 30khz to 1 1mhz.
Say 1 end is the computer and the other end is the router or say 1 end is the cable modem and the other end is the router which ends of the above gears should i choose to put.
Each time the cable goes through the center of the toroid counts as one turn.
The magnetic field generates throughout the cable.
I was starting to see more errors than normal i m currently running from a temporary set up while re fitting my study and since fitting the ferrites i think things have been slightly better.
From a device or to a device.
A conductive cable acts as an antenna if the device produces radio frequency energy this can be transmitted through the cable which acts as an unintentional radiator in this case the bead is required for regulatory compliance to reduce emi.
Use 2 4 ferrite toroid with mix 43 and wind the cable through 7 turns to get an impedance over 1 000 ohms measured data.