...yes, but the various theories, some of which seem relevant, hint at dissipation of leaders can reduce direct hits through the use of various elevated conductors. The Wikipedia article refers to the improvement that the Tesla structure provided over the original lightening rod pointed spikes. But, of course, that's Wikipedia.
Also, there are many minor strikes that can damage open wiring but not affect the inside of a conduit. As a ham radio operator with a lightening arrester in line with the coax, I can attest to the snap, crackle, and pop that occurs inside that darned thing during any nearby electrical storm. What does a 2" spark do to unprotected equipment? . . . j o n a t h a n -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Scott Reed Sent: Tuesday, May 22, 2007 8:33 PM To: WISPA General List Subject: Re: [WISPA] FM Radio and Ethernet Nothing stops direct hits. A spark that traveled through miles of air isn't really going to care what else is between it and the ground. Good ground is the lifesaver for nearby hits that induce wild voltages. And following the code is always best for the health and safety of the people. Jonathan Schmidt wrote: > This has been my experience, Scott. > > I have seen lightening enter an enclosed device and simply burn a hole right > in the middle of a circuit board with nothing else damaged. > > On my desktop PC, lightening apparently came in through the cable, through > the cable modem (destroyed) and down the Ethernet, through the Linksys (OK) > to the PC and the only other damage was the motherboard Ethernet. I > replaced the modem and bought a PCI Ethernet card and it's fine. What paths > lightening took in this incident or the above incident is anyone's guess. > > There is still controversy over the value of diverting or directing > lightening and/or lightening leaders and streamers to protect against a > direct hit. > > It's really fascinating and here's a fun place to start you thinking: > http://en.wikipedia.org/wiki/Lightning_rod > > Nevertheless, good enclosures fed with metal conduit that's well grounded > appear to do well but the local ordinances need to be heeded. > > . . . j o n a t h a n > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Scott Reed > Sent: Tuesday, May 22, 2007 5:35 PM > To: [EMAIL PROTECTED]; WISPA General List > Subject: Re: [WISPA] FM Radio and Ethernet > > If properly grounded, the opposite is true. The ground wire should > direct the lightning to ground (hence the name) and away from your > equipment. > > Not to mention that in the case of an equipment failure that causes the > power supply to put 120VAC on the case, etc., the ground wire directs > the current to ground, not you. It is always about safety. I would > much rather have dead equipment than dead personnel because an > electrical system was not properly grounded. > > Dennis Burgess wrote: > >> YOU DO NOT WANT TO RUN A GROUND WIRE! The reason for that, is that >> then it >> gives lightning etc the ability to go though your equipment vs the tower >> ground! B >> >> >> >> >> On 5/22/07, Scott Reed <[EMAIL PROTECTED]> wrote: >> >>> Again, >>> Check your local code before you copy this. No ground is not allowed >>> here, unless somehow you can prove it is a temporary extension cord. >>> Neither is low voltage in same conduit at 120VAC. >>> >>> That said, small changes to Dennis' configuration will make good >>> installation. >>> >>> Run the cat5 in a separate (metallic) pipe (rigid, EMT, Sealtite, >>> whatever you like). Ground the bottom of the pipe. I would leave the >>> top ungrounded, but that is: >>> 1) personal preference (eliminates ground loops). >>> 2) determined by which way gives you the best performance, least >>> interference from the FM. >>> You may want to use cat5e or cat6 as the twist is tighter, thus >>> accepting less interference as well. >>> >>> Run a ground wire with the power. Even for the low current required at >>> the top, I would probably run 14AWG or 12AWG. Lowers the inductance, may >>> allow less noise to be induced on the power leads. Besides, 14AWG is >>> the smallest wire you can run with a 15amp breaker. Same thing with >>> ground loops; I would probably use a plastic box and thus isolate the >>> power ground from the enclosure, tower, etc. >>> >>> One good way to do it is consult a local commercial/industrial >>> electrician. They will know the code for your area. But they don't >>> always understand radio and induced voltages. >>> >>> >>> Dennis Burgess wrote: >>> >>>> We are located at 400 foot on a FM tower, 100,000 watts at the top of >>>> 1400 >>>> foot. >>>> >>>> The total length of CAT 5 is 440 foot or so, and plug directly into a >>>> RB532 >>>> at the top of the tower (power at the top as well) >>>> >>>> We ran a felexable conduit up the tower, inside, 16awg solid >>>> >>> copper, one >>> >>>> black, one white, (for the 110), NO GROUND, and also in that same >>>> conduit, >>>> we ran good outdoor, sheilded CAT5, UV Resistant (even though it is >>>> >>> fully >>> >>>> enclosed), and we get a 100meg link without issues for the most part! >>>> >>>> One thing we did do, is ensure that we were on the other side of >>>> >>> all the >>> >>>> transmission lines running up the tower. >>>> >>>> Dennis >>>> >>>> >>>> >>>> On 5/22/07, Andrew Niemantsverdriet <[EMAIL PROTECTED]> wrote: >>>> >>>>> I am co located on a tower with an FM transmitter. The FM station >>>>> >>> runs >>> >>>>> at 105Mhz. We were running one AP at 10 half duplex to overcome the >>>>> havoc that the FM station created on our ethernet feed. We now >>>>> >>> need to >>> >>>>> run that link at 100 full duplex to be able to handle the traffic >>>>> coming through it. What are some hints tips tricks to make it work. >>>>> >>>>> The cable run itself is 150' of shielded CAT5. It works fine at 10 >>>>> >>> H/D >>> >>>>> and it works at 100 F/D most of the time but it will occasionally go >>>>> down and there is some intermittent packet loss on that link. The run >>>>> itself terminates into a managed switch. >>>>> >>>>> If CAT5 won't work, is fiber my next option? How does that work? I >>>>> assume that I need power up the tower as well? Any tips to make that >>>>> happen assuming keeping the existing CAT5 won't work. >>>>> -- >>>>> WISPA Wireless List: wireless@wispa.org >>>>> >>>>> Subscribe/Unsubscribe: >>>>> http://lists.wispa.org/mailman/listinfo/wireless >>>>> >>>>> Archives: http://lists.wispa.org/pipermail/wireless/ >>>>> >>>>> >>>> >>>> >>> -- >>> Scott Reed >>> Owner >>> NewWays >>> Wireless Networking >>> Network Design, Installation and Administration >>> www.nwwnet.net >>> >>> -- >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >>> >> >> > > -- Scott Reed Owner NewWays Wireless Networking Network Design, Installation and Administration www.nwwnet.net -- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
