Anyone have experience with running RJ-45 cable through areas where close proximity to 120VAC power cables is unavoidable?
I've been keeping my cable runs a minimum distance of 6 inches from all sources of power, but I'm now facing a particularly brutal wiring area where I have no choice but to follow a cluster of 120VAC power cables that also happen to feed several fluorescent lights (I don't think this area could get much worse).
I don't have any shielded RJ-45 cable, and given how many network cables I want to run through this "hot-spot", I doubt I could afford going that route.
Instead, I've picked up some 2 inch diameter steel conduit. My plan was to run the RJ-45 cable through these pipe segments when I get close to the power and fluorescent lights. I was then going to run a permanent grounding wire to the sections of conduit.
However, something made me doubt whether this would be a perfect solution when I first considered it - and as it's been a long time since I've taken a physics course, I couldn't really figure out why. Anyway, something I read on Slashdot today added to my doubts.
From http://slashdot.org/comments.pl?sid=41591&cid=4394400 :
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"CRT monitors are affected more by low-frequency EMI than the RFI computers emit.
A simple test: Take the lid off of your case, and place it beside the monitor. Nothing strange happens.
Next, place an AC-operated fan, transformer-based soldering iron, or similar magnetic device next to the monitor, and watchen das blinkenrainbow.
That said, flat peices of steel (such as that which comprises your case) do very little to counteract low-frequency magnetism, while aluminum does absolutely nothing. Common steel can have some low-freuquency shielding effect if it's curved just so, but that's usually impractical. (there's other stuff, such as Mu-Metal, which is formulated with the specific goal of blocking EMI, and does work quite well. But it's expensive, and hard to find.)
I have to be careful where I put my Best FerrUPS because the large ferroresonant transformer in it will cause monitors to shake from several feet away.
Problems with computer-generated RFI generally show up with radio and television. I can't listen to an AM radio anywhere near my apartment with the PCs on, and there's a few FM stations that I can only recieve outside or in the back bedroom, away from the machines.
My neighbors must hate me for it, as I'm sure it's not much better anywhere in the building. But the 300-pound, heavy-footed woman upstairs has four kids who wake up at 5:30 AM daily, and the people directly beside me have a bad habit of listening to one-note bass lines with their lousy, one-note subwoofer, directly on the other side of the wall behind my desk.
So, I guess I care a lot less about RFI than I do about proper cooling. Thus, the top of the case is completely absent, allowing all kinds of natural, quiet convection cooling to take place."
-----------------------------------
I realize this quote is referring to the impact an open PC case might have on sensitive electronic components - and "low-frequency magnetism" sounds altogether bogus to me - but it does bring up the point that there is a difference between radio frequency interference and magnetic fields.
I think the steel conduit will protect my network cable from any RFI generated by the fluorescent lights, but I'm not sure if it will do anything to protect against the magnetic fields generated by the power cables. Those magnetic fields could easily induce stray voltages in my network cabling - and I'm not sure that the steel conduit would do anything to stop those magnetic fields.
Then again, shielded TP network cable is rated for use in areas where power cables will be close by, is it not?
So what about the grounded, steel conduit idea of mine? How would the end result be any different than if I'd used shielded TP network cable? Does either option provide protection against both RFI and magnetic fields? Do I even need to worry?
There are times when I wish I'd done my degree in electrical engineering.
I've been keeping my cable runs a minimum distance of 6 inches from all sources of power, but I'm now facing a particularly brutal wiring area where I have no choice but to follow a cluster of 120VAC power cables that also happen to feed several fluorescent lights (I don't think this area could get much worse).
I don't have any shielded RJ-45 cable, and given how many network cables I want to run through this "hot-spot", I doubt I could afford going that route.
Instead, I've picked up some 2 inch diameter steel conduit. My plan was to run the RJ-45 cable through these pipe segments when I get close to the power and fluorescent lights. I was then going to run a permanent grounding wire to the sections of conduit.
However, something made me doubt whether this would be a perfect solution when I first considered it - and as it's been a long time since I've taken a physics course, I couldn't really figure out why. Anyway, something I read on Slashdot today added to my doubts.
From http://slashdot.org/comments.pl?sid=41591&cid=4394400 :
-----------------------------------
"CRT monitors are affected more by low-frequency EMI than the RFI computers emit.
A simple test: Take the lid off of your case, and place it beside the monitor. Nothing strange happens.
Next, place an AC-operated fan, transformer-based soldering iron, or similar magnetic device next to the monitor, and watchen das blinkenrainbow.
That said, flat peices of steel (such as that which comprises your case) do very little to counteract low-frequency magnetism, while aluminum does absolutely nothing. Common steel can have some low-freuquency shielding effect if it's curved just so, but that's usually impractical. (there's other stuff, such as Mu-Metal, which is formulated with the specific goal of blocking EMI, and does work quite well. But it's expensive, and hard to find.)
I have to be careful where I put my Best FerrUPS because the large ferroresonant transformer in it will cause monitors to shake from several feet away.
Problems with computer-generated RFI generally show up with radio and television. I can't listen to an AM radio anywhere near my apartment with the PCs on, and there's a few FM stations that I can only recieve outside or in the back bedroom, away from the machines.
My neighbors must hate me for it, as I'm sure it's not much better anywhere in the building. But the 300-pound, heavy-footed woman upstairs has four kids who wake up at 5:30 AM daily, and the people directly beside me have a bad habit of listening to one-note bass lines with their lousy, one-note subwoofer, directly on the other side of the wall behind my desk.
So, I guess I care a lot less about RFI than I do about proper cooling. Thus, the top of the case is completely absent, allowing all kinds of natural, quiet convection cooling to take place."
-----------------------------------
I realize this quote is referring to the impact an open PC case might have on sensitive electronic components - and "low-frequency magnetism" sounds altogether bogus to me - but it does bring up the point that there is a difference between radio frequency interference and magnetic fields.
I think the steel conduit will protect my network cable from any RFI generated by the fluorescent lights, but I'm not sure if it will do anything to protect against the magnetic fields generated by the power cables. Those magnetic fields could easily induce stray voltages in my network cabling - and I'm not sure that the steel conduit would do anything to stop those magnetic fields.
Then again, shielded TP network cable is rated for use in areas where power cables will be close by, is it not?
So what about the grounded, steel conduit idea of mine? How would the end result be any different than if I'd used shielded TP network cable? Does either option provide protection against both RFI and magnetic fields? Do I even need to worry?
There are times when I wish I'd done my degree in electrical engineering.
