Bringing the grounding discussion here!

[northgeorgia]

Over in the FTA forums, we've been having an interesting discussion about grounding satellite systems. I want to pose the same question here.

Are your outdoor antennas grounded, and if so, could you describe how you've done it?

 

[navychop]

Mine is not.


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[boba]

Over in the FTA forums, we've been having an interesting discussion about grounding satellite systems. I want to pose the same question here.

Are your outdoor antennas grounded, and if so, could you describe how you've done it?

Are you questioning satellite grounding or over the air antennas? your posting history suggests your interest is in Free To Air antennas. If you use the search function there is already many threads taking up a lot of space on grounding satellite systems.

 

[northgeorgia]

Are you questioning satellite grounding or over the air antennas? your posting history suggests your interest is in Free To Air antennas. If you use the search function there is already many threads taking up a lot of space on grounding satellite systems.

No, I am specifically asking about over the air antennas.

 

[kittyhas1000legs]

My UHF antenna isn't grounded. I've had no problems so far.


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[northgeorgia]

Thanks for the input. I'm hearing a lot of people mention it's better not to ground a satellite system to the home electrical ground because it may attract lightning even more. I've seen a lot of diagrams for grounding OTA antennas that seem to do just that, and wondered if it is equally as bad an idea.

 

[Blindowl1234]

I've never grounded my OTA or FTA setup. No problems here so far. With all the trees around me lightening would probably hit one of those first..I hope anyway.

 

[harshness]

OTA grounding is the same as dish (and AM/FM/Sirius/XM) grounding from the standpoint of NEC article 810 (unless transmission is involved). You're expected to ground the support frame of the antenna as well as using an Antenna Discharge Unit on any RF cabling. If there is a rotator present, that's article 725.

Here's a handy summary:

http://ecmweb.com/code-basics/article-810-radio-and-television-equipment

 

[northgeorgia]

Thanks, harshness. So according to the NEC, at least from the diagrams, it seems they do want you to ground OTA antennas (and satellite dishes) to the house electrical ground. Interesting.

 

[jayn_j]

From my HAM world, the rule was always a strong ground strap to a solid earth ground. Would not like to see this running through the house Romex to the box. Just plain wrong

 

[jorgek]

Grounding is also to help discharge any static buildup on the antennas. Most lightening damage is usually due to surges coming in via the power lines from nearby strikes. Having said that all my antennas, OTA, FTA and Ham radio are grounded and coax have inline surge suppressors as well.

 

[Bob2011]

The most confusing thing about grounding antennas to me is if it is ok to ground the antenna to its own grounding rod. I purchased some four foot grounding rods on clearance last year for the purpose of grounding my dishes and antennas but NEC doesn't say anything other than one common ground for the whole house. Running wires from the antennas all the way around the house to the electrical panel would be pricey if you use the heavy gauge wire NEC recommends.

 

[sergei]

I purchased some four foot grounding rods on clearance last year for the purpose of grounding my dishes and antennas but NEC doesn't say anything other than one common ground for the whole house.

To get a good ground you need a grounding system that reads 25 ohms or less, most systems are using 8 foot 5/8 inches thick rods, that's the only thing i use. You might not have the equipment to measure it but I would question using a 4 foot one that were on clearance as they might be counterfeit and will not meet NEC code.

 

[harshness]

According to the NEC, anything you ground an antenna to must be a bonding point. Next, you look up what a bonding point is.

Everything having a separate ground rod is not NEC. NEC says they must all be tied together in a specific way (bonded).

None of this comes together until you understand bonding points.

 

[rglore]

Lighting also travels through the ground from nearby strikes, different points in the ground will have different voltages. That is why all ground rods must be bonded to each other with heavy gauge cable to prevent huge voltage and current surges between ground points through your cables. Better and code required to only use a single ground rod for the house and connect all other grounds to something that's directly connected to it. An exception is a dish or antenna that's higher than it's surroundings and is a likely lighting target. Then it requires it's own ground rod which then must be bonded with 6 guage copper to the main ground.

 

[jayn_j]

According to the NEC, anything you ground an antenna to must be a bonding point. Next, you look up what a bonding point is.

Everything having a separate ground rod is not NEC. NEC says they must all be tied together in a specific way (bonded).

None of this comes together until you understand bonding points.

Have a friend who spent early years as a phone installer for ma Bell. He tells the tale of installing a phone in a building next door to an electric substation. He was standing on the ground and touched the ground wire post on the phone line and got a serious shock. When he measured, he found that the phone company ground and the electrical ground differed by nearly 400 volts!

I would also add to the grounding rod discussion that the length of the rod is not as important as the conductivity between the rod and the surrounding earth. Not a big deal in soggy Wisconsin, but back in Colorado, I always made sure that my ground rods were within the throw radius of my irrigation system. Damp earth is a much better conductor than dry earth. Just common sense, but often not considered.

 

[Bob2011]

So if the 4 foot rods I bought on clearance from MCM are not legal why do so many places still sell them? I did a little reading and lots of HAM radio guys use them in arrays to ground their towers. Those guys are usually educated about electronics so why would they not install to code.

I never installed them and I get the feeling grounding my antennas would make them more of a lightning target. They are ten feet below the roof peak on a chimney and at least 50 feet from the nearest tree that is 70 feet tall. I always felt it was a low risk that they would be struck by lightning.

 

[jayn_j]

So if the 4 foot rods I bought on clearance from MCM are not legal why do so many places still sell them? I did a little reading and lots of HAM radio guys use them in arrays to ground their towers. Those guys are usually educated about electronics so why would they not install to code.

I never installed them and I get the feeling grounding my antennas would make them more of a lightning target. They are ten feet below the roof peak on a chimney and at least 50 feet from the nearest tree that is 70 feet tall. I always felt it was a low risk that they would be struck by lightning.

That isn't how a lightning rod works. The theory is that a low resistance path to a solid ground will discharge before a large charge accumulates. The higher the resistance, the higher the voltage before the arc occurs and the higher the current passing through the ground path. An ungrounded antenna still has a path to earth ground, but it is through a relatively high resistance of wet wood, shingles, etc so the charge will be a lot higher before it discharges. Since we are talking a very large capacitor in that cloud, a big bunch of current is going to flow through everthing in its path, and that is your TV, DVR, house wiring, modem and anything else that gets in the way.

So, to say it another way, the low resistance ground path is not to handle all the current of a lightning strike, but to encourage the potential to discharge well before it gets to that point.