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Hi everyone,


I have the following setup with my HDTV/UHF antenna and my DirecTV satellite dish. My antenna came with a pair of diplexers. This allows to me to connect both the satellite dish and UHF antenna on the roof to one diplexer on the roof. The diplexer on the roof then connects to a single RG-6 cable down to my living room. Then, the second diplexer in my living room splits the signal back to separate outputs (Satellite IN and Antenna IN) going to my HDTV DirecTV receiver.


(See attached diagram--To those of you who are wondering why I am going through the mess of this diplexer stuff, the other 3 of my 4 DirecTV outputs from the dish going into the house are being used by other DirecTV receivers)


Anyway, the one thing I am afraid of is that lightning could strike the antenna on the roof, and send a blast of electrical energy straight into my HDTV receiver through the Sat IN and Antenna IN jacks, thereby frying it. I would like to know a simple, cheap, and effective way to ground the antenna and/or the entire system to protect my equipment.


Thanks!
 

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See http://www.avsforum.com/avs-vb/show...light=grounding


AVSforum member Signal posted the following helpful sites.


National Electrical Code - Search for "dish"
http://forums.nfpa.org:8081/necfaq/necsrch.htm


Preventing Damage Due to Ground Potential Difference
http://www.cinergy.com/surge/ttip08.htm


PSIHQ - Grounding Requirements
http://www.psihq.com/iread/strpgrnd.htm


PolyPhaser Technical Information
http://www.polyphaser.com/ppc_technical.asp


Tower Page - see N1LO's GUYED TOWER TOPIC SUMMARY
http://www.qsl.net/n1lo/tower.htm


Basically, you want to ground the dish mast, the antenna mast, and the coax where it enters the house with a grounding block.
 

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With my system, Sprint Broadband WAN, UHF/VHF/FM antenna, VHF antenna, oval DirecTV dish with triple LNB, I run a 10 gage cooper wire from each piece that has a ground lug (4x4 switch, all the masts, etc) and run the ground wire to a 8 ft grounding rod. I don't have a metal water pipe to the street so I don't connect to the water main also. At the point where the coax goes into the house I have a grounding block on each coax which is also connected to the grounding rod.
 

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An important thing to do if you connect your dish/mount/coax grounds to a grounding rod is that the grounding rod be connected to the main electrical service entrance grounding rod.


If you don't, there's a voltage potential between the two grounds which may cause no end of trouble.
 

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Ok, I read most of the links provided by greywolf and I have a specific followup question. I hope it's simple.


I just put up an antenna and ran the ground wire across my roof and hooked it onto the electric service box. This is where the cable and phone companies attached their ground wires.


Is it safe to just have the ground wire going across my roof or should I ground the antennae to a grounding rod at the front of the house and then run a wire from there all the way around the house to the electric service?


Thanks,


Greg
 

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Greg, I'm hardly well versed in the ins and outs of this sort of thing, but take my opinion for a direction of what to look at when seeking an answer:


It is my belief that the grounding path for an antenna should be the closest you can have/most direct between the antenna and a grounding point.


Thus, if there's potential for the ground path created by the coax cable through your equipment to the electrical service wiring ground to the service entrance ground to end up being a shorter path than what you've wired, it would be better to go directly to a grounding rod near the antenna, and to bond the grounding rod to the main electrical service grounding point.
 

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Proper ground connections serve three purposes in electronic circuits.

1) They provides a return path for the intended current flow.

2) They permit certain devices whose performance is potential sensitive to operate optimally and,

3) They provide a path for unintended surges from lightning and high-potentail shorts to be diverted safely and thereby reduce fire and shock hazards.


Grounding of the mast and coax is required only for safety. The Model National Electrical Code is a fire and safety code, not a technical performance guideline.


In grounding, shorter is better than longer, straighter is better than crooked, larger gauge is better than smaller gauge, and vertical is better than horizontal, but frankly, if your installation meets the code, the added safety benefit of exceeding it is minuscule at best. Some people who are concerned about the hazard effects of lightning strikes drive an 8 foot ground rod directly below the mast and bond it to the system ground with 6 gauge or larger wire so as to form a more efficient path to divert the lightning from whatever they are trying to protect, but the people who have collaborated on the development of the Model Code don't consider this significantly beneficial so as to require it.


The audio hum bars sometimes seen on video screen and the deep hum sometimes heard on speakers do not come from inadequate or improper safety grounding. They come from grounding in a manner that forms ground loops and are best remedied by isolation of the affected, low voltage circuitry.
 
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