wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY
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1 edit | Will burying a feed line ground the CPE?
If I were to set up an AP in a house, and wanted to mount the antenna outside would this create a lot of grounding issues? I was thinking about mounting an omni on a pole or large tree 75 feet or so from the house. My idea was to simply bury the cable that runs from the antenna and then bring it up right near the house (I am assuming this would ground it??). Is this possible or would lighting stay in the cable and enter the house, thus frying the AP and starting a fire? 
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp | Direct bury...or in PVC or something similar?
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wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY
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| Thats a good question, would either suffice? I just added a "picture" of what I am asking to help you understand. Also, how deep would it need to be for this to be viable?
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
 ·CenturyLink
| reply to wifi4milez
You will need to use a suitable lightning arrestor at the point where it enters the house...
By the way...that is a lot of cable. It will kill your signal, both ways.
And water WILL get in the cable and ruin it.
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wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY
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| I have read that the lighting arrestors are not really effective, and that the only way to really protect the equipment is proper grounding. Any thoughts on that? Also, I could theoretically put a POE amp just below the omni to counteract the cable loss, correct?
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
·CenturyLink
| Regardless of whether they are effective or not...you are still obligated to ground the system in a Code compliant manner.
An amp may or may not help you. Do a link budget calc and see what it shows. The preference is to NOT use amps...unless necessary.
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wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY | Fair enough, how would you suggest accomplishing this task then if running the cable will be problematic?
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John Galt
Forward, March
Premium
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Happy Camp
·CenturyLink
| The Code requires that you ground the antenna where it enters the house.
You could also put the cable in PVC conduit from the "mast" to the house to keep it dry. You will have to seal where it enters and exits from the conduit to keep water from pooling inside the conduit.
As far as the loss issues..use sufficiently large cable to cut losses to a minimum.
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wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY
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| Would I need to drill small drainage holes in the bottom of the PVC every few feet? I am still a bit unclear as to if this setup would disperse some or all of the lighting in the event of a strike (even when using arrestors). If not, there wouldnt be any point to burying the PVC other than aesthetics.
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
·CenturyLink
| Do a search and go back and read some of the recent postings on lightning.
There are a number of good references here...
Once you become better informed the answers that you are seeking will be readily apparent.
The Polyphaser site is good:
»www.polyphaser.com/ppc_ptd_home.aspx
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bito
Premium
join:2001-10-08
Atlanta, GA
| Why don't you mount the AP up with the omni and thereby eliminate all of your RF loss? Assuming the AP is PoE capable. Then ground the antenna/arrestor/AP at the base of the mast with a ground rod. That way, all you have to bury is the cat5 cable. I would imagine that 100' of gel-filled cat5 is a heck of a lot cheaper than 100' of LMR 
That's my 2/5 of a nickel anyways.
Caleb |
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wifi4milez
Big Russ, 1918 to 2008. Rest in Peace
join:2004-08-07
New York, NY
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| Thats a pretty good suggestion. Cant lighting travel down catv as well though? I would still need to use an arrestor prior to entering the house if I am not mistaken (thats fine by the way).
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| said by wifi4milez  :Thats a pretty good suggestion. Cant lighting travel down catv as well though? Yes, Lightning can follow any type of conductor anywhere. Since the CAT5 has copper, it is a conductor, It will usually take the least path of resistance, hence everyone trying to give it one and guide it away from our gear.:)
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bito
Premium
join:2001-10-08
Atlanta, GA
| reply to wifi4milez
Next to a beer, this is one of the best $3 you can spend:
»www.radioshack.com/product.asp?c···=61-2144
Up to 10kA current suppression, clamps at 60-90V. Won't handle a direct strike on it's own, but if your AP takes a strike and you have it properly grounded then it should be enough to handle any leftovers from the initial spike. Your AP will be in flames in a puddle on the ground, but this should keep you from blowing up the customer's router/computer/any-damn-thing-else-that-is-connected-to-it.
I was in the shop one night last month when we took a direct strike to our omni rig on the roof. It instantly fused the POS arrestor we had on our coax run and blew the radio, but it wasn't done yet. Apparently it had enough juice to come through the PoE injector, down the data cable into our switch, then proceded to blow a gateway (bits burned out over the course of 10 minutes, slowly the lights started to blink away and never come back), a server (through the LAN to blow the board and power supply, but the RAM and HDD were ok), our DSL modem, then over the phone line to blow out the filter. The building next to ours took a spike on the phone lines at the same instant that blew up their router and server, don't know if we sent that their way or not. Apparently it kept just enough voltage going through it to blow everything, and then when it was fully convinced it had enough destruction for one night, the whole damn thing when critical and the cables at the AP EXPLODED. Also, it blew the top off the omni and VAPORIZED a full foot of the metal element inside. It blew the damn connectors off of the omni side of the LMR. Blown off, as in loosened and then blown off and found on the ground. Funny enough, i redid the end of the cable with the same connectors and it works fine.
I was sitting in the same room with all the gear when it blew. It made a pop so loud that I couldn't hear out of my right ear for about 10 minutes. Oh, and it killed the big roll-up door, so I had to muscle my way out of there. I could have sworn something inside blew up. I didn't know what happenend until I realized my internet feed was tanked.
Needless to say, the next day is when we started looking for better protection 
Moral of the story: Take as many precautions as you can when it comes to lightning protection. Lightning is some crazy sh!t, and it hates your equipment
Caleb |
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robbin
Premium,MVM
join:2000-09-21
Leander, TX
| reply to wifi4milez
Just a little semantics here. I would never consider any lightning protection device to be a lightning arrester -- that suggests that it stops the lightning. I believe newer thinking is that it is lightning suppression. Maybe a small difference, but a big difference.
In answer to the original question, if you have your cable buried in the soil and lightning strikes anywhere in the nearby area, you may have an induced charge enter your line simply because it is buried. In other words, it wouldn't even have to hit the tree to cause you problems.
One other thing, you can't do a proper install with lightning suppression without having proper grounding. They are not the same though-- you can have proper grounding without lightning suppression, but not the reverse!  |
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DaDogs
Semper Vigilantis
Premium
join:2004-02-28
Deltaville, VA
| reply to wifi4milez
Once upon a time ...
I had a long (~120') run of RG-58u coax between two buildings. I had had a bit of "thin lan" running on each end and the two networks were bridged across the coax. The networks had been removed and the coax just hung there between the buildings with nothing connected to either end.
One day a thunderstorm came up and when I got to the office my entire network was down. I had to replace half the modems in the house and half the servers had to be rebuilt. Mind you everything was on surge supression.
The repairs took about a week. The following Moday, almost to the minute one week later, a thunder storm came along. I was sitting there in my server room when lightening struck a building about fifty yards away. I heard a "pop" and was looking right at the end of that coax when a spark jumped about an inch from the end of the coax to a surge supressor on the network.
It took out about half my modems and the rest of my servers.
Yep, lightening is some crazy stuff. That current was INDUCED current, and there was plenty of it too.
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wispman
join:2004-12-21
USA | Is it enough to put it in your TOS that it is subs responsibility to ground everything? |
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John Galt
Forward, March
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Happy Camp
·CenturyLink
| said by wispman :Is it enough to put it in your TOS that it is subs responsibility to ground everything? Grounding is the responsibility of the installer.
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rfnut
Premium
join:2002-04-27
Fisher, IL | reply to wispman
No. It is not enough. Would the phone company include clause that suggested the homeowner provide proper bonding to the system? no. They would not. If you place eq. on a subs home, you are responsible for the entire installation meeting code. |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| said by rfnut :No. It is not enough. Would the phone company include clause that suggested the homeowner provide proper bonding to the system? no. They would not. If you place eq. on a subs home, you are responsible for the entire installation meeting code. Yep!!!. If You are doing the job, You are responsible for making sure it works in the end. There is NO WAY to pass the buck on issues like this, I don't care what lawyer draws up the contract, the precedent has been set, and You butt will hang for doing something stupid:D
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