| To ground or not to ground.... This is a question based on REAL WORLD experience. I've got a Canopy 430 AP and the Moto install manual says to use a shielded cable with the ends grounded at the top and the bottom of the tower. So far everyone I have talked to says that's what the manual says but I will be sorry if I ground both ends.
Thoughts ? |
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| Do it.
Motorola's manuals state that, and as such you should follow it. The 430 has the external antenna so they require the surge protector at the top and at the bottom, and then the CMM has built in protection so you are good to go. |
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 davidgGood Bye My FriendPremium,MVM
join:2002-06-15
none | reply to battleop
if you follow the manual then have issues at least you may get things warrantied. if you don't ground it per the manual, they could claim that is the cause of any failure.
as a side note, some contractors were sent to a site to redo R-56 to current revision. prior to their being on site it had taken 1 damaging strike in several years. after the changes, it took about 3 damaging hits in as many months. just goes to show that no matter what you do, lightning can find a way to screw things up!
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine! |
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| said by davidg:if you follow the manual then have issues at least you may get things warrantied. if you don't ground it per the manual, they could claim that is the cause of any failure. as a side note, some contractors were sent to a site to redo R-56 to current revision. prior to their being on site it had taken 1 damaging strike in several years. after the changes, it took about 3 damaging hits in as many months. just goes to show that no matter what you do, lightning can find a way to screw things up! Not surprising. They are constantly revising R56. Heck just last year the ST we were working with at the time was telling us stuff that had not yet been put into the manual (he sits on the board of ST's and Engineers who write the Bible) on how to do this and how to do that, what things they are changing to previous suggests, etc.
As anything in this business, its 50% math and 50% trial and error. 
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"No job is so important, and no service is so urgent that we cannot take the time to perform our work safely."
-- AT&T, Your World, Destroyed.
--Safety One Tower Rescue Certified
--LLigetfa:"Wimax is like teenage sex. Everyone talks about doing it." |
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I would gut feeling on this if the site was not 890 miles away, up 240'. If I take a strike it's a minimum of 6 hours of down time on that AP until I am able to send some of my guys to get properly trained to climb.
I've had some very reputable people tell me to not ground the shield on the cable on both ends but do ground the radio it's self. I've had some other reputable people tell me to ground it. |
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said by battleop:I've got a Canopy 430 AP and the Moto install manual says to use a shielded cable with the ends grounded at the top and the bottom of the tower. The manual is correct. Generations of experience have proven this necessary. If you do not, harmful voltage differences between the tower and cable can result due to differences in wave propagation.
Of course, the cable and tower must both connect together at an earth ground at the base. Also for same |
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said by battleop: I've had some very reputable people tell me to not ground the shield on the cable on both ends but do ground the radio it's self. That obviously makes the radio an ideal canidate for surge damage. Earthing should be at the tower base. And where the cable enters the building. Not grounding the shield and grounding the radio says that person has no respectable electrical reputation.
Meanwhile, its not just grounding. Which ground? Bond to the tower. Earth at its base. All are grounds that are electrically different. |
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lutfulPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
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said by battleop:Moto install manual says to use a shielded cable with the ends grounded at the top and the bottom of the tower Motorola installation manuals are essentially "best practice" for the whole WISP industry. I have often uploaded relevant extracts with extra comments.
FYI you can actually bond cable shields to tower/mast more than twice - every 10-20 feet if you desire - each bond will contribute to even better surge protection. Anyway the 2 bonds at top and bottom are essential for lightning surge protection of both outdoor equipment and indoor stuff. 
said by battleop:So far everyone I have talked to says ... I will be sorry if I ground both ends. Simple (mis)understand of classic "ground loop" ... a professional surge protector's grounding lugs are actually completely isolated from signal and electrical grounds during normal operation. They become connected for just a few microseconds during a surge event. |
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| My gut feeling is to not ground. I really think that I have a better chance of the AP surviving thunderstorms. However in a "Cover my ass" move I am going to elect to do it the Moto way. That way if when it gets smacked I can always say " Well that's how Motorola said to do it. |
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WHT
join:2010-03-26
kudos:3 | reply to battleop
said by battleop:I've had some very reputable people tell me to not ground the shield on the cable on both ends but do ground the radio it's self. I've had some other reputable people tell me to ground it. We ground the foil shield at the bottom of the tower just before it goes into the station protector. At the top of the tower, we cut a ring in the foil shield. The portion of the foil shield that is on the radio side of the cut, we bond to the mast. |
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keefe007Premium
join:2004-02-24
Germantown, WI | reply to battleop
said by battleop:My gut feeling is to not ground. I really think that I have a better chance of the AP surviving thunderstorms. However in a "Cover my ass" move I am going to elect to do it the Moto way. That way if when it gets smacked I can always say " Well that's how Motorola said to do it. That is crazy. It is true that someone could screw up grounding so bad that they end up with something worse than no ground, however, it is simply not correct that an ungrounded system will have a better chance of surviving thunderstorms than a properly grounded system.
We have towers that regularly take lightning strikes and due to proper grounding we never have equipment damage.
On the flipside I've seen other local WISPS, who do not ground properly, lose equipment every time a storm rolls through. |
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jcremin
join:2009-12-22
Siren, WI
kudos:2 | said by keefe007:On the flipside I've seen other local WISPS, who do not ground properly, lose equipment every time a storm rolls through. And on the flipside of your flipside, there are plenty of WISPS who do not ground properly and never have any equipment damage.
Lightning is a unpredictable beast. If only it were consistent |
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