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Guest Message by DevFuse

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Is Your Dish Grounded?


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56 replies to this topic

Poll: Is your dish grounded? (181 member(s) have cast votes)

Is your dish grounded?

  1. No (69 votes [38.12%])

    Percentage of vote: 38.12%

  2. Voted Not sure (7 votes [3.87%])

    Percentage of vote: 3.87%

  3. Earth Ground (55 votes [30.39%])

    Percentage of vote: 30.39%

  4. House Ground (50 votes [27.62%])

    Percentage of vote: 27.62%

Vote

#41 OFFLINE   Nick

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Posted 24 June 2007 - 06:42 AM

Mine too, so my installer used wireless grounding. He said it's his favorite way to install.

:lol:

But seriously, on what frequency does your wireless ground transmit?

Inquiring minds want to know. :rolleyes:

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#42 OFFLINE   joed32

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Posted 24 June 2007 - 09:23 AM

Not sure but I think it's O2

#43 OFFLINE   MarkA

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Posted 25 June 2007 - 05:13 PM

"Lightning (like all electricity) wants the path of least resistance, but will take what it can get... so the point of any lightning rod is to make an attractive point for the lightning and route it away from all your stuff."

WRONG, it's this fundamental misunderstanding that results in so many ungrounded dishes. The point of a lightning rod is to *repel* lightning by draining the static discharge.

The secondary function of the ground is to help safely drain away static energy - not a direct lightning strike however - you'd be done for if that happened.

A grounded dish is less likely to get struck by lightning, and provides safety against secondary static energy charges.

#44 OFFLINE   prospect60

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Posted 22 July 2007 - 08:18 PM

Thank you Mark.


Yes or No vote on mine.

1) Roof mounted AU9 dish with 4 Coax and an 8AWG (it may even be a 6) solid copper wire with the green insulation stripped at the end.

2) 8AWG solid copper wire attached at the ground hole of dish runs 6-8 feet to Port 1 of dual port dual coax ground block1.

3) A separate 8AWG copper then attaches to port 2 of block1 and runs through ground port of Dual Coax Ground Block 2. It was once a single continuous run of copper wire from the Dish to both Ground Blocks and then down to the ground, but when I moved the dish the old wire had to be extended.

4) The second run of copper wire continues from the 2nd Ground block and runs 30-40 feet along the roof gutter and down the outside of the downspout. It is attached to what I assume is a thick copper wire that runs down from the Electric Power Meter and is attached to a Rod buried in the ground -- looks like the shape of the copper ground rods that I've seen at Lowes. It looks like the ground from the cable box and telephone is attached at this same wire from the Electric Meter.

5) The 4 coax cables from the LNBs run to the pair of Ground Blocks and then 4 additional coax from the Ground Blocks enter the house about 2-3 feet away through the attic. Eventually I suspect those 4 incoming wires will attach to a Zinwell Multiswitch inside the attic, but right now I only need 4 outputs

6) CM4228 currently is in the attic.

If something doesn't sound right I do have access to the installer and will beat some retribution out of the schmuck since I (ugh that should be he) swore it was down correctly.

#45 OFFLINE   harsh

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Posted 22 July 2007 - 10:16 PM

While often practiced, daisy chained grounds aren't code. The ground screw on each device (dish, ground block) are to be home run all the way to a bonding point. Bonding points don't happen between the ends of another wire.

Will poorly done grounds still bleed off the static? Certainly better than no ground.

#46 OFFLINE   Richard King

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Posted 22 July 2007 - 10:41 PM

While often practiced, daisy chained grounds aren't code.

I always find this interesting. If the installer had used a four position grounding block in place of two two (no, I don't do ballet) position grounding blocks there would be no question. Once wire from the dish to the four position GB and then on to the grounding post and all is fine. The same grounding wire going through one block then the other block, probably side by side, then to the grounding post is a problem. :shrug: While I am sure the code frowns on this, I can't see the logic. But then, I'm in the process of trying to get a building permit at the moment and logic seems to have nothing to do with that either. :(
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#47 OFFLINE   prospect60

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Posted 22 July 2007 - 11:24 PM

Wow, that's not what the DirecTV installation brochure shows.

So it should have 3 separate runs of Copper wire back to the grounding point (one from the dish and one from each grounding block)?

Is the Bonding Point the actual ground rod or does that go the wire (?4AWG) that runs from the Electric meter to the Ground Rod. That's the wire where the Telephone and CATV boxes appear to be 'attached' to the House Ground. I assumed that wire was the proper place since the House Inspector signed off and the Telephone installer, Electrician, etc who built the house all did the same.

If not it looks like I have to get more green wire and get back to work.

If the installer had used a four position grounding block in place of two two (no, I don't do ballet) position grounding blocks there would be no question. Once wire from the dish to the four position GB and then on to the grounding post and all is fine.


Is that correct or would you then run 2 separate lines, one from the dish and then one from the Ground Block. I just a lot more confused though that would certainly simplify the fix as I could just replace the 2 dual blocks with a quad.

#48 OFFLINE   DawgLink

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Posted 25 July 2007 - 03:40 PM

No. They put it on my roof

#49 OFFLINE   Richard King

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Posted 25 July 2007 - 05:32 PM

The problem that I have with an independent ground to the dish is that the LNB is part of the dish electrically and it is grounded through the coax. If you add a ground wire at the dish (or the base of the dish) you are, in theory, creating a ground loop. Many ages ago, when I was doing recording studio work, ground loops were a real problem that a person could spend many hours chasing down to create a clean audio flow. Having two routes to ground from one piece of equipment was always found to be the problem. Which piece of equipment and how to resolve was what required the detective work. This type of thing was always to be avoided yet, it appears to me, that it is encouraged by the installations mentioned above. My theory on grounding is that the coax goes to the ground block and the ground block grounding wire goes to the house ground, end of story. No potential ground loop is created.
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#50 OFFLINE   Richard King

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Posted 25 July 2007 - 05:40 PM

After a bit of rethinking, actually, the LNB's are not part of the dish since they are not electrically connected to the dish, but are connected to the dish with a plastic collar. So, I guess to do it "correctly" they are actually two pieces of equipment and so would require independent runs back to the house ground. I would still go LNB to Ground block and Dish to Ground Block then Ground block to house ground (ground pole). Another theoretical question is "Why ground the dish at all?" The dish is just a piece of metal attached to the house but not to any electrical equipment of the house. It has no electrical connection to the house at all. Why ground it?
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#51 OFFLINE   Tom Robertson

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Posted 25 July 2007 - 08:21 PM

Wind blowing across the surface of the dish can build up a fair amount of potential (depending on the actual surface material of course).

And the operation of the LNBs is based on a common ground plane between the LNB and the IRD and the optional switch. Mess with the ground, and things go bad.

You are absolutely correct, all the ground points must be tied together to the same ground via very low resistance connection or loops will occur.

Cheers,
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#52 OFFLINE   Richard King

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Posted 25 July 2007 - 09:31 PM

Wind blowing across the surface of the dish can build up a fair amount of potential (depending on the actual surface material of course).

Yep. Agree. But, where would that charge dishcharge, er, discharge to? With no direct path to ground the nearest place to discharge to would be the shield of the RG-6 cable (through a spark jump if enough charge should build up) and then to the ground block and to ground through the block. Then again, the theory of grounding the dish is to avoid the buildup of a charge in the first place and, because of the charge, the possibility of attracting a lightning strike. If you think too much about this kind of thing it can drive you crazy. :lol:
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#53 OFFLINE   CableSux

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Posted 25 July 2007 - 10:01 PM

Grounding has always been a contentious issue. Anyone that has read the NEC and spent any time trying to decipher it realizes there are 2 sections, one was written for TV antennas (especially towers the stick 30-40-50 feet into the sky) and the other is CATV (cable) where cable wires cross power lines.

The problem with satellite is, since it doesn't seem to really fall under either, they force installers to use BOTH! They use the TV antenna code for grounding the dish (mast) and the CATV code for grounding the cable.

The reason to ground CATV is 2-fold, 1 to protect against shorts with power lines and 2 to re-reference ground before the cable gets to your equipment. Satellite doesn't need to do either unless you're running cables over/under power lines.

The reason for grounding TV antennas and towers is pretty obvious. If a tower falls over and hits power lines or many times lights are installed on TV towers... they have AC power going to them.. protect against shorts. Anyone that's read the NEC knows they are only worried about grounding the "mast". They aren't worried about the cable, probably because until a few years ago, they only used 300 ohm cable, the flat stuff with no shield. You can't ground that! So... the NEC wants the satellite dish "mast" grounded. Not the dish, the mast.

Ground mast (from one code) + ground coax (from another code) = 2 grounds.

In reality... most satellite dishes are all metal. That means the coax shield (which one code wants grounded) is electrically attached to the rest of the metal dish, to include the "mast". use an ohm meter to verify. So technically, the mast and coax shield are the same point. Logic says ground the coax and you've grounded the "mast". The exception would be those dishes that have a plastic yoke, like the Dish 500. But here's where logic really upsets code-lovers... if the dish, I.E. mast is separated from the LNB, then it's just a piece of metal on the roof... why does it need to be grounded? It's no longer electrically connected to the house. It's not going to fall over onto power lines. It's not going to have yard lights mounted to it. :D

Now the real question is... has anyone, anywhere, ever heard of lightening hitting a satellite dish (grounded or not) or electrocuting anyone because it wasn't grounded? I have seen grounding cause more problems because of improper wiring in houses. But that's for another day. :)
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#54 OFFLINE   Richard King

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Posted 26 July 2007 - 07:21 AM

Well stated Mr. Sux. I have seen a BUD or two get hit by lightning (and does that ever make a mess), but can't say that I have ever seen a pizza dish ever get hit, grounded or not.
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#55 OFFLINE   DogLover

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Posted 26 July 2007 - 07:55 AM

Now the real question is... has anyone, anywhere, ever heard of lightening hitting a satellite dish (grounded or not) or electrocuting anyone because it wasn't grounded? I have seen grounding cause more problems because of improper wiring in houses. But that's for another day. :)


Not the dish, but I have had lightning hit the LNB, or at least close enough to the LNB to fry it and leave scorch marks. (In fact in created a large enough charge in the air to turn on my electric toothbrush. Half asleep on a rainy Saturday morning, that produced a very twilight zone moment as my brain tried to process what happened.) This was probably 10+ years ago when first with D*.

Luckily, I was within whatever warranty period they were offering. They send a replacement LNB right away. Said they would charge me if the returned LNB showed lightning damage rather than just a manufacturers defect. They obviously never looked at the bad LNB, because damage was obvious. They never charged me for replacement.:)
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#56 OFFLINE   CableSux

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Posted 26 July 2007 - 11:51 AM

I agree that grounding a dish provides for reducing the potential of attracting lightening. By the same token, it can't guarantee it won't be hit. Just like the tree in your yard can be hit, and you can bet it's well grounded :) Grounded or not, nothing will protect against a direct hit or a "feeler" from a nearby strike.

The question comes down to, if the purpose of the ground is to reference the dish (mast) to the house/earth ground, then isn't the shielding in the coax, being grounded through your AC outlet sufficient? Technically, yes. BUT... there's always a "but" isn't there? lol BUT, what if the customer only has a two-prong plug (although technically, the return side of the outlet is connected to ground).. or the plug isn't wired correctly. By having the installer install a ground block and ground it to the house/earth ground, we avoid that risk.

Soooo, when you say your LNB was hit, it probably didn't make any difference if it was grounded or not. The metal casing on the LNB is electrically connected to the coax shield, which is electrically connected to the receivers chassis and ground and return side of the AC power cord, which is electrically connected to the house ground, which is connected to the earth ground... :)
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#57 OFFLINE   CableSux

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Posted 27 July 2007 - 05:38 AM

What really bugs me is how strict everyone is about grounding satellite dishes (and their cables) but yet TV antennas and towers (for which NEC 210 was specifically written) are almost never grounded.... and we never hear a peep about it. Someone should start a poll asking everyone if their TV antenna tower is grounded. :)
Joel Munn
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HughesNet, Hughes Mobile, Starband, iDirect, Viasat, Motosat, DTN, EMNet, GTech, ComLabs, FTA, SBCA Certified (only until Feb 07, Oops! Expired. Oh well) [to be continued]...




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