Ethernet RFI

[Moleculo]

For some time I've been trying to get rid of RFI on 20m from the ethernet cable that runs from my living room into the den where my radio equipment is. It also happens to run right underneath my antennas. I've tried everything can't get rid of it. Wrapping it around about 5 really big torroid cords with 5 wraps lessened it by quite a bit, but didn't completely eliminate it. I've seen threads on other sites about the same issue, but noone seems to know the cure. I know that the connectors on the cable are proper as I did them myself and was a network engineer in a former life. I'm not sure what else to try but I'm willing to give any suggestions a shot.

 

[Captain Kilowatt]

Slide a piece of old coax braid over the cable and ground both ends. That will completely shield the cable. If it still causes RFI then call a priest and have him perform an exorcism.

 

[W5LZ]

Mole',
I know I'm not telling you anything new, but the biggies are isolation, shielding, and by-passing... and distance. A combination of those things will usually get rid of, or reduce any interference to at least a manageable level.
It sounds like you are on the right track with the huge torroid. Ever wondered why I usually recommend a 5 gallon bucket of torroids as a nice thing to have around, besides it just sounds funny? Something you will definitely know more about than I do, is to try isolating the cable. Sort of like what's done with audio, a capacitor in-line with the signal line. A 0.001 ceramic cap works with audio, no idea what it would do to a digital 'hi/low' type signal. Take that for what it's worth. And when you do figure out what works, let me know too!
- 'Doc


Just for grins, did you know that on TVs with the CRT tube, under all that itty-bitty copper wire in the yoke there's a very nice large torroid? Two or three of them will do the same as that 5 gallon bucket full of the little ones (almost).

OH! QRN just reminded me of that midget hula girl with the rattles and who is painted blue dancing along the path of that cable. Works every time!

 

[dudmuck]

Since an ethernet cable is connecting between two machines, either side could be generating the RFI. Unplug each side individually to find which side is generating the problem, and then put the ferrites on that side. Or maybe both sides are offending, so both sides would need ferrite.

If its only 10/100 (and not 1000Mbit), then only four wires are used.
You can see here that the brown & blue pairs arent used at 10/100 speeds
Ethernet crossover cable - Wikipedia, the free encyclopedia
If thats the case, then cut those four wires off at the offending end of the cable.

Finally, you can run each remaining wire individually through its own ferrite bead to improve effectiveness. This is ok for 10/100, but not recommended for gigabit.
But in any case, make sure the ferrites are a close to the cable ends (connectors) as possible.