Well, Sunday I tried to see if I could get rid of the RFI coming from the ethernet cable that runs from den to living room, directly underneath my HF antennas. For point of reference, the noise is a high pitched, two tone warbling, very loud. It's present right on 14.210mhz.
The hub/router is located in the den near the radio equipment. If I unplug the cable going to the living room, the RFI goes away. Several other pieces of computer equipment plugged into the switch/router cause no RFI. If I unplug the far end device, the RFI goes away. It doesn't matter what I plug into at the other end (hub, xbox, directv receiver, pc, etc.) it comes back.
I bought a 7' patch cable, stripped off the jacket and wrapped the whole length of both the TX pair and RX pair each on their own ferrite core. The ferrite was a pretty decent sized one and I got probably 30 wraps or so on it. Attached the patch cable to a couple and attached the equipment. That didn't make a dent on the RFI
.
Next I played with some ceramic capacitors to see if I could figure out which pair the noise comes from. It took both a .01uf and .001uf cap in parallel to get rid of the noise on the TX pair only at the far end (living room). Neither cap was enough to get rid of it completely, but both together axed the RFI. But the bad news is that this also now killed the ethernet connection completely. So for future reference: bypass caps on ethernet is a bad thing.
So it appears that the strength of the RF for an cable run directly under an HF antenna is just too great unless you're going to use some kind of shielded cable or fiber. I'm not sure what else that can be done at this point except switch to a wireless system.
As a side note, the noise can be notched out by a decent rig...but I was hoping to get rid of it from the source.
The hub/router is located in the den near the radio equipment. If I unplug the cable going to the living room, the RFI goes away. Several other pieces of computer equipment plugged into the switch/router cause no RFI. If I unplug the far end device, the RFI goes away. It doesn't matter what I plug into at the other end (hub, xbox, directv receiver, pc, etc.) it comes back.
I bought a 7' patch cable, stripped off the jacket and wrapped the whole length of both the TX pair and RX pair each on their own ferrite core. The ferrite was a pretty decent sized one and I got probably 30 wraps or so on it. Attached the patch cable to a couple and attached the equipment. That didn't make a dent on the RFI
.Next I played with some ceramic capacitors to see if I could figure out which pair the noise comes from. It took both a .01uf and .001uf cap in parallel to get rid of the noise on the TX pair only at the far end (living room). Neither cap was enough to get rid of it completely, but both together axed the RFI. But the bad news is that this also now killed the ethernet connection completely. So for future reference: bypass caps on ethernet is a bad thing.
So it appears that the strength of the RF for an cable run directly under an HF antenna is just too great unless you're going to use some kind of shielded cable or fiber. I'm not sure what else that can be done at this point except switch to a wireless system.
As a side note, the noise can be notched out by a decent rig...but I was hoping to get rid of it from the source.
