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Home » Forums » Forum Archives » Networking and Internet Sharing » Topic # 622

EMI/RFI and Cat5 cable
diletante Feb-01-01 10:34 PM
We are installing a network on an aircraft. Cat5 cable is in the plan so far. Some of the cable runs may be long (greater than 100 ft.) and in general all sorts of cables get bundled together. I wonder if there is an equivalent to Cat5 cable that is robust in tough EMI/RFI environments? We must not interfere with aircraft systems, and we don't want to be interfered with either.

Rob


1. RE: EMI/RFI and Cat5 cable
lbyard Feb-01-01 11:51 PM
In response to message 0
I would be more worried about EMI/RFI emitted by the CAT 5 cable. I don't think I would put unshielded cable running at 100 Mhz/BPS in an aircraft. 100 Mhz is pretty close to an emergency VHF frequency, if I recall correctly. I think a review of the FAA regulations, etc. should be made on the subject. Also, the effect on airport equipment (homers, TACAN, tower receivers, etc.) should be looked at; although an aircraft is probably a pretty good Faraday cage. Surely, someone has networked a plane before. I would try to find them. Shielded CAT 5 cable is available. Larry

2. RE: EMI/RFI and Cat5 cable
diletante Feb-02-01 03:52 AM
In response to message 1
I agree with you about the RFI potential. I was in a meeting and they just dropped it on me that they were going to use Cat 5 ("just like we use in the office"). We won't be going anywhere until there have been extensive EMI/RFI tests, and I sure don't want to get that far and find out there is a problem.

On the other hand, the people who made the suggestion have certainly been around airplanes. Airplane people are funny about RFI. They won't let you operate a laptop during takeoff and landing, but they will let you fill the plane with racks of PCs and monitors, with cables running every which way.

Since I suggested looking for something like shielded Cat 5, I agreed to look into it even though networking is not my thing. I figured you would know if there was such a thing, so I just dropped a note here before calling it a day. Thanks for the help, Rob


3. RE: EMI/RFI and Cat5 cable
KeithF Feb-05-01 01:38 AM
In response to message 2
Being Ex-Forces (1900 & Frozen to Death Ago!) I can remember a boatload of regs from both CAA (UK) & FAA (US) on signal propagation and development/signal emmision etc. I really think you should be contacting someone in an authority (Preferably in the Country where you reside) If you think about it sensibly, even STP (Sheilded Twisted Pair) CAT5 has excelent noise factor cancelling ratio's... Only When Grounded... One assumes your Aircraft Fly's (Not Grounded/at Earth potential !...) Best Wishes & Good Luck

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