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Hi ya folks,


Just wondering what the minimum requirements are for grounding a roof-mounted antenna.


National Electrical Code (NEC) says grounding the mast to a ground rod and installing an arrestor/discharge unit tied to the ground rod for the coax near the ingress to the house.


What if you only get the coax grounded via the arrestor? Is this enough?


Thanks,

Errol


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[This message has been edited by kealii (edited 12-13-2000).]
 

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Bothe the mast and the antenna cable should be grounded. Use seperate ground wires to each and make sure that they are bonded to the house ground rod


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I agree with stuigi. Two other acceptable grounding procedures would be to ground to a cold water pipe or to the house' electrical service panel. Careful on the latter! Be sure to pull the main fuses before drilling holes in the metal if that becomes necessary and brush or vacuum any metal shavings out. The idea of grounding is both for signal integrity and, more importantly, safety. Your antenna and mast are effectively a lightning rod. NO LIGHTNING ROD AND GROUNDING PROCEDURE WILL CHANNEL AN ACTUAL LIGHTNING STRIKE SAFELY TO GROUND, THOUGH. The grounding will, however, hopefully channel atmospheric static charges to ground BEFORE they can build to lightning potential.
 

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I realize this thread is dated, but I will try anyway:


I am in the process of installing D* and OTA antenna for HD reception. The question is: Where does one locate an "arrestor" for usage with an Antenna Rotor cable? I have searched (with no luck) for this elusive device!


Also of interest to the grounding of the OTA antenna was is the following passage in the 1999 NEC handbook referring to NEC 820-40(d) (page 948):


"The most common error made in grounding CATV systems is to connect the coaxial cable sheath to a ground rod driven by the CATV installer at a convenient location near the point of entry to the building and not bonding it to the electrical service grounding electrode system, service raceway, or other system. ....(more)"


and then this:


"Both CATV systems and power systems are subject to current surges as a result, for example, of induced voltages from lightning in the vicinity of the usually extensive outside distribution systems. Surges also result from switching operations on power systems. If the grounded conductors and parts of the two system are not bonded by a low-impedance path, such line surges can raise the potential difference between the two systems to many thousands of volts. This can result in arcing between the two systems, for example, whenever the coaxial cable jacket contacts a grounded part, such as a metal water pipe or metal structure member, inside the building. ..."


"Section 820-40(D): BONDING OF ELECTRODES. A bonding jumper not smaller than No. 6 copper or equivalent shall be connected between the antenna systems grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used."



Which sent me to the local building supply to procure approx 100 feet of No. 6 copper to connect the grounding rod from my OTA antenna, the D* dish, the cable tv service entrance, the telephone service entrance, all to the electrical service entrance!!


Anyone else have similar experience?


TIA,

NE
 

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A detailed discussion of grounding techniques is here . Clipping from my comments there:


One last thing for those of us in the county, never ever bond to the water pipe! This may work well in the city (though I have concerns there as well since it will enter the house), but in the event of a strike you will be replacing your pump since it can be an excellent ground!



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Amateur Electronic Supply (AES). They're a HAM Radio & CE supply place. Their web page: www.aesham.com ,(800)558-0411. They sell a variety, including PolyPhaser.


They're also a good source for high-pass filters (for radio interference), cable, connectors, rotors, coax switches, and Winegard Antennas.


FWIW


Scott


 

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If a supplemental ground rod is used, it must be bonded to the building grounding electrode system with a minimum of a No. 6 copper conductor. If these separate grounds are not bonded together, a very large difference in ground potential can develop across, and equalize through, your satellite receiver, TV tuner, etc. Check your local codes. More information about grounding:
http://www.cinergy.com/surge/ttip08.htm
http://www.psihq.com/iread/strpgrnd.htm
http://www.powerclinic.com/tex01.htm
http://www.powerclinic.com/images/te1fig1.gif
http://www.polyphaser.com/ppc_technical.asp
http://www.qsl.net/n1lo/tower.htm
http://forums.nfpa.org:8081/necfaq/necsrch.htm (search for "dish")
 

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Quote:
Originally posted by Man E:

One last thing for those of us in the county, never ever bond to the water pipe! This may work well in the city (though I have concerns there as well since it will enter the house), but in the event of a strike you will be replacing your pump since it can be an excellent ground!
If you don't bond to the water pipe, then you're not in compliance with the NEC. Section 250-2(c), "General Requirements for Grounding and Bonding", "Bonding of Electrically Conductive Materials and other Equipment": "Electrically conductive materials, such as metal water piping, metal gas piping, and structural steel members, that are likely to become energized shall be bonded as specified by this article to the supply system grounded conductor...". In other words, the water pipe has to be tied to the service panel ground; you don't have a choice.


I don't know what your well is like, but on mine the water pipe is bonded to a steel well casing driven into the ground, supposedly to bedrock. The pump itself is 160 ft. underground, under about 50 ft. of water. And some of the piping down to it is PVC. I have hard time believing a lightning strike would make it down that far before being dissipated.


NakedEngineer,


Yea, I ended up installing alot of 6 AWG copper to connect the two grounds. The DSB dishes are on the side of the house opposite the Service Panel. It is very important keep all grounds tied together, for the reasons you cite.


I didn't bother with an arrestor for the rotor cable either, primarily becuase I couldn't find one. FWIW I have one of the older, non-electronic rotor controllers. Looking inside these things, they're very robust (basically a motor, transformer, some microswitches); I fiured they could withstand a surge or two so I simply made sure to plug it into a surge suppressor as it has no connection to the rest of the system. If I lived in a lightning-prone area I might have been more careful.

 

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From the resources given above, I was able to find a rotor control protector http://www.avsforum.com/ubb/biggrin.gif on the http://www.aesham.com/pdf.html website (catalog section 14, near the end). The unit is manufactured by PolyPhaser (PLY ISRCT POLYPHASER 8WIRE ROTOR PROTECT $54.99).


Anyone have a recommendation (for or against) this unit? If I could afford the risk http://www.avsforum.com/ubb/frown.gif , it would be cheaper to have a spare rotor control!! All kidding aside... anyone?


Also, two more questions. Presently a Radio Shack VU-190XR antenna (approx 13 feet in length) is mounted on a 5 foot pole atop the rotor. Is the 5 foot extension too long, for example should it be cut down to around 2 feet to reduce the chance of wind damage to the rotor, and should some form of ground wire be used to jumper from the antenna section above the rotor to the grounded mast below the rotor?


Thanks in advance!

NE


(And especially thanks to those for the above posted links. They were very helpful in my stage of the "learning curve"!!)




[This message has been edited by NakedEngineer (edited 04-09-2001).]
 

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Quote:
Originally posted by BarryO:

If you don't bond to the water pipe, then you're not in compliance with the NEC. Section 250-2(c), "General Requirements for Grounding and Bonding", "Bonding of Electrically Conductive Materials and other Equipment": "Electrically conductive materials, such as metal water piping, metal gas piping, and structural steel members, that are likely to become energized shall be bonded as specified by this article to the supply system grounded conductor...". In other words, the water pipe has to be tied to the service panel ground; you don't have a choice.


I don't know what your well is like, but on mine the water pipe is bonded to a steel well casing driven into the ground, supposedly to bedrock. The pump itself is 160 ft. underground, under about 50 ft. of water. And some of the piping down to it is PVC. I have hard time believing a lightning strike would make it down that far before being dissipated.
That's a wicked-assed pump ya got there Barry. In which desert do you reside http://www.avsforum.com/ubb/wink.gif Mine is at most 65 feet (and I don't think it's even that far). It is a 220 pump that is directly connected to the panel (or it wouldn't work). This is different than connecting a "lightning rod" to a water pipe that may meander through the house (which is my larger concern, city or country). It may or may not effect the pump, but then why would one invite the opportunity? As to the NEC code above, I guess that I'll have to read the whole thing in context because I cannot believe for the life of me, or my family, or yours that they would actually be suggesting that one bond a natural gas pipe to an electrical discharge device. Seems like there could be a problem with that.



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The Tower Page http://www.qsl.net/n1lo/towers.txt has information (recommendations by Polyphaser) about using MOVs to protect rotor control lines (see GROUNDING FEEDLINES).


My rotor does not provide electrical continuity, so I bonded the masts above and below the rotor using ground clamps and a coil of No. 8 stranded copper.


[This message has been edited by Signal (edited 04-10-2001).]
 

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well depth depends on how far you are above the water table; I'm in foothills at about 350' elevation. The guys higher up with 800-900' deep wells really had to pay through the nose http://www.avsforum.com/ubb/wink.gif


The idea behind grounding the gas pipe is to prevent any static buildup on the lines and dissipate them safely to ground. BTW the 1999 Natiobal Electrical Code is available for download at www.nfpa.org; I think they charge about $50 for it.


Remember a direct lightning strike is very rare, and anything short of a professional lightning rod system won't make any difference, anyway. Far more likely are voltage surges induced by nearby strikes, power surges on the power lines, and surges on phone lines when they short on HV power lines. The NEC guidelines are intended to prevent damage from these events.
 

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My well pump is about 120 feet down (about 40 feet of water above it), 220V and there is not one foot of metal piping in either supply or drain systems (it's all PVC, PEX, or polybutulene). Grounding to my water pipes would be an exercise in futility/stupidity. And you really think it is smart to ground propane gas lines ?!? I do need to get around to finishing up my grounding on both DBS and OTA (but 6AWG ?) - all coax is grounded to a ground rod (not tied to to the main yet). Maybe with spring finally here I can get around to the job.
 

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I've read through all of the material here and most of the links that have been posted and it got me thinking about how I am grounded.


Let me start by saying I live in the city. The coax from my dish is grounded to a water pipe at the rear of my house before entry. The coax from my VHF/UHF antenna is grounded to a water pipe in the front of my house before entry.


After reading the interestig article here < http://www.dbsforums.com/reviews/tech1_5.html > I realized that I really don't know if these pipes are grounded to the house ground in the service panel, which means that the potential between the coax and the receiver could be different. In continuing to read the same article, surge protectors are mentioned. I am using a Curtis surge protector that both the satellite and UHF/VHF coaxes pass through.


Wouldn't they be grounded at the surge protector (and definitely grounded to the house ground)? Would this mean I could safely (and should) remove the grounds to the water pipes which could be changing the potential? It seems that with or without the Curtis box this would be the case since the receiver is grounded to the house ground.


Dave


[This message has been edited by davebach (edited 04-11-2001).]
 

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aaaarrrrghghghhhhhh!


Grounding!!!



Ok, davebach, let me say that I do know a lot about grounding (from previous job experience).


First, the man grounding to natural gas was just kidding.


Second, grounding to the water pipes is BECAUSE they are just as likely to carry a charge INTO the house as the electric service, therefore it is crucial that everything that COULD be electrified by lightening be TIED TOGETHER.


Simply, if a electrical (potential) difference exists between the water pipe and the building ground it could electrocute ya. (Not to say that those with deep wells are not in a slightly different category as far as protection needs....)


PLEASE CHECK THE NEC. IMHO (in my humble opinion) you SHOULD have the electrical system grounded to the water pipes as well as all other systems (i.e., CATV, antenna, dish, tower, and grandma).


Just hoping to be coherent at this time of night!


NE
 

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Thanks for clearing that up... I will immediately ground grandma to the natural gas line. heh.


Dave
 

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Your homeowners insurance company may differ.



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Quote:
Originally posted by Man E:

Your homeowners insurance company may differ.
Exactly. On one side, you have the National Fire Protection Association, publishers of the NEC. They have a 100+ year sucessful history of promulgating safety standards. Every three years, they assemble the best safety experts and engineers in the industry to update the NEC.


The NEC says to 1.) ground the antenna mast, 2.) ground the coax shield where it enters the house, and 3.) ensure all these grounds are tied to the house ground with a low impedance connection.


Not doing things according to the NEC is illegal in most locales, and can be effectively used by insurance companies as a reason to deny a claim.


On the other side, you have a posting on some website whose main claim to validity is that it was reviewed by a relative to happens to be an engineer. It contains some useful information, but it also contains some dubious and flat-out wrong claims (apparently derived from other dubious web sites), such as:

Quote:
The earth is an enormous sponge for electrons. This is caused by ionization of materials deep within the mantle (as their electrons are stripped off and become either involved in other nuclear reactions or attached to other materials, iron and silicon in the core become positively charged). So the earth can be thought of as holding an extremely large positive charge.
?? Electrons do not get involved in nuclear reactions, and what goes on in the mantle has no effect on grounding. The earth has a net neutral charge. Lightning will be attracted due to a basic static electricity process that occurs whenever a charged object (a cloud) is brought close to a conductor (the surface of the earth). The part of the conductor closest to the object acquires a charge opposite that of the object, as the object drives electrons in the conductor away to it or toward it depending on whether the object is negatively or positively charged, respectively.

Quote:
lightning rods are not designed to attract lightning, but rather to repel it.
Lightning rods neither repel nor attract lightning. A lightnig strike will occur on or in the vicinity of your home when the electric field strength in the air above your home gets high enough to exceed the voltage breakdown point of the air. It makes no difference whether or not a lightning rod, or an antenna, is present. Lightning rods take advantage of the property that the electrical field strength is higher near pointy objects. Thus, when a strike does occur, it will tend to occur at the rod, and hopefully will be dissipated to ground through the hefty ground system used with lightning rods.


Grounding an antenna has no effect on whether or not a strike will occur. But if it does, the intent of grounding is to ensure the resulting voltage surge induced on the antenna system is safely dissipated to ground.


I'd suggest looking up the NEC at the library or download it from the NPFA site, and following what it says.



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You have a right to install OTA and dish antennas on property under your control.


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