Grounding antenna that is away from house

[jstoddard]

Hello,

I live in a Canyon. When I bought the house, there was a tv antenna mounted at the top of the canyon behind my house. It's on a 10' pole driven into the ground, attached by guy wires. The antenna is pretty much destroyed and I want to replace it with a new one, and start using it, but I'm concerned about grounding. I'm assuming I drive a grounding stake in the ground beside the antenna and run a copper wire from it to either (a) the pole itself or (b) to the antenna (Not sure which) Does this sound right to you guys? Any suggestions would be appreciated.

Thanks,

Jerry

 

[jayn_j]

Hello,

I live in a Canyon. When I bought the house, there was a tv antenna mounted at the top of the canyon behind my house. It's on a 10' pole driven into the ground, attached by guy wires. The antenna is pretty much destroyed and I want to replace it with a new one, and start using it, but I'm concerned about grounding. I'm assuming I drive a grounding stake in the ground beside the antenna and run a copper wire from it to either (a) the pole itself or (b) to the antenna (Not sure which) Does this sound right to you guys? Any suggestions would be appreciated.

Thanks,

Jerry

deciding on a ground strategy is tricky. What you suggest makes sense from a lightning standpoint and would be good if the antenna was at the house. You don't mention the length of the cable run, but if it is significant, there could be a significant voltage potential between the antenna and the house ground. simply attaching the coax would cause significant current flow through the coax shield.

A friend of mine put himself through college by doing installations for the local phone company (this was before the breakup). He was installing a new line in an office building that was next door to a power substation. Following standard procedure, he drove a ground rod into the soil at the junction box. On a hunch, he put a voltmeter between the phone ground and the ground rod and measured over 400 volts. We tend to think of ground as an absolute, but in fact it is a relative reference and can vary over distance. Note, the 400 V is an extreme case, but I have seen 50-70V.

Be careful of this and be prepared to isolate/mitigate the grounds through use a a buried copper braid that can handle any current flow.

 

[bhelms]

Shouldn't the grounded portion of the antenna system (mast, frame, ground rod, etc.) be bonded back to the house ground at the electrical entrance with 6ga. copper or such?

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[jayn_j]

Shouldn't the grounded portion of the antenna system (mast, frame, ground rod, etc.) be bonded back to the house ground at the electrical entrance with 6ga. copper or such?

Sent from my LG-E980 using the SatelliteGuys app!

Agreed. That's what I was trying to say in the last paragraph. A good reference which will bury the layman in tech details is online from the IEEE:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

Look starting at page 30 for the sections describing ground potential differences.

 

[harshness]

Shouldn't the grounded portion of the antenna system (mast, frame, ground rod, etc.) be bonded back to the house ground at the electrical entrance with 6ga. copper or such?

The idea is to not create a lightning rod. Grounding the mast or boom of the antenna to the house ground does exactly that because of the potential difference between where the antenna is mounted and where the house is situated (as jayn_j pointed out). I imagine that the antenna itself should be grounded where it stands (to not make it a lightning rod) and the cable coming down should be grounded where it enters the house (as ALWAYS).

 

[jstoddard]

Thanks for the responses. So, I ground the antenna to a grounding stake. But what are the mechanics of grounding at the house--I mean I've looked up the way you normally ground a rooftop antenna to a house. But if I'm following you, and I'm only bringing the TV cable line down to the house, am I going to attach the shield portion of the cable to ground? Is that what you mean? And if so, is there a handy-dandy easy way to do that--some kind of adapter? My cable will be running quite close to the breaker box. I really appreciate your help. I'm no electrician.

 

[jayn_j]

Thanks for the responses. So, I ground the antenna to a grounding stake. But what are the mechanics of grounding at the house--I mean I've looked up the way you normally ground a rooftop antenna to a house. But if I'm following you, and I'm only bringing the TV cable line down to the house, am I going to attach the shield portion of the cable to ground? Is that what you mean? And if so, is there a handy-dandy easy way to do that--some kind of adapter? My cable will be running quite close to the breaker box. I really appreciate your help. I'm no electrician.

Depending on how that post is buried, you may already be grounded at the antenna end. An additional copper rod can't hurt though. What I am trying to say is to take a voltmeter and measure the voltage difference between the coax shield coming from the antenna and the house ground at the grounding rod where the electrical service enters the house. If there is a significant voltage between the two (measure both AC and DC), you will be carrying current through the coax shielding. If it is a small amount, you can manage it by adding a grounding block and tie it to the ground rod for the house. If it is larger than a few volts, you would be better off burying a grounding cable (bhelms suggests 6 Ga, and that should be OK unless the voltage difference is over 100V. It depends on voltage and length of coax) and tying both ends to the ground rods.

In addition to the safety hazard, a voltage difference between the two ends can cause ground loop type interference. That shows up as buzzing on audio and used to be wavy lines on NTSC. Not so much on digital signals though.

Reality check. Unless you are near some major facility, substation, etc, I don't expect there will be a significant difference between the grounds and you can safely just run the coax into the house. However, the grounding block is always a good idea at the house.

 

[harshness]

And if so, is there a handy-dandy easy way to do that--some kind of adapter?

An example: Amazon product ASIN B001I5610E
These should be installed outside the home but immediately inside will accomplish the goal.

They sell these things at hardware and home improvement stores. I don't recommend paying extra to get a brand name.

In one side and out the other. A wire connected to your house's ground stake goes in the hole and you tighten down the screw.

With coaxial cable, make sure you don't bend it any tighter than about 3" radius and use a "drip loop" (Google is your friend) before going into the block and the outer wall.

 

[jstoddard]

Thanks so much to all for the information. I deeply appreciate it. I'll use the voltmeter as jayn_j suggested--I'm an audio engineer so I have a little understanding of ground loops and voltage differentiation on ground wires--emphasis on the "little." Really appreciate the pic of the Coaxial Grounding adapter--I'd never seen one of these and wouldn't have known how to search for it. Thanks!

 

[Titanium]

Voltage potential readings will vary by seasonal changes as the moisture in the soil changes the conductivity. The multiple ground rods are creating a simple dry battery. Unless the voltage is equalized between these points, voltage will be present on the distribution.

Grounding faults can occur due to defective power grid facilities and these must be addressed by the power company on their side. Bonding multiple ground points will eliminate the efffect, but not remedy the cause.

Using the coax shield to bond the tower ground to the structure ground would not meet any electrical code and could present a shock hazard. I have received a major shock while grabbing a coax line and the grounding block during a service call. Got in the habit after that to brush the block with the coax and look for sparks and measure whenever possible. The coax ground block will prevent the voltage from entering the structure, but does not eliminate the issue. There is no substitute for a dedicated bonding wire between the tower ground and the structure ground.

 

[harshness]

There is no substitute for a dedicated bonding wire between the tower ground and the structure ground.

And that turns the antenna into a lightning rod. This is one of those situations where you have to pick your battles and getting "tickled" when you're not careful is surely better than bringing the lightning to your home.

 

[Titanium]

Bonding multiple grounding points to the structure ground does not turn the antenna into a lightning rod and will not bringing lightning into the home. If the antenna and/or tower is properly grounded, the NEC required dedicated bonding is one more preventive measure to divert an electrical event to a ground without passing through the home.

 

[jayn_j]

And that turns the antenna into a lightning rod. This is one of those situations where you have to pick your battles and getting "tickled" when you're not careful is surely better than bringing the lightning to your home.

I've learned not to get into pissing contests with you, but I do wonder if you know the real purpose of a lightning rod. Hint: it isn't to attract lightning strikes.

 

[Titanium]

If you are concerned with lightning entering the home through the coax, nytie 4 or 5 loops (one or two feet in diameter) before the line enters the home.

The best lightning arrestor type uses a gas discharge tube. Some models offer a user replaceable cartridge. Here is an example of a quality arrestor that I have used on my Ubiquiti PTP:
https://www.solidsignal.com/m/product.aspx?p=TW-LP-N-J-BHJ

 

[Troch77]

If you are concerned with lightning entering the home through the coax, nytie 4 or 5 loops (one or two feet in diameter) before the line enters the home.

The best lightning arrestor type uses a gas discharge tube. Some models offer a user replaceable cartridge. Here is an example of a quality arrestor that I have used on my Ubiquiti PTP:
https://www.solidsignal.com/m/product.aspx?p=TW-LP-N-J-BHJ

Since we are on the grounding subject.
Im mounting this Antenna 30 feet up, it will be bolted to my roof peak.
I also have a metal roof.

How should I ground this antenna?

 

[Titanium]

Is the metal roof grounded?

Use flat strap to ground the mast to the roof. Make sure the metal roof is grounded to the structure ground.

Use a ground block (attached to structure ground) on the coax before entering the structure.

On a side note: raise the antenna as high as possible above the metal roof as the proximity it will greatly influence the antenna's performance and design characteristics.

 

[Troch77]

Is the metal roof grounded?

Use flat strap to ground the mast to the roof. Make sure the metal roof is grounded to the structure ground.

Use a ground block (attached to structure ground) on the coax before entering the structure.

On a side note: raise the antenna as high as possible above the metal roof as the proximity it will greatly influence the antenna's performance and design characteristics.

Thanks it will actually be out in front of the roof on the facia.
So the direction of the signal would hit the antenna before my roof.
It would be out in front and away about 1 foot. And probably 3 feet higher.

The metal roof isn't grounded.
Im not sure thats even a code requirement.

So I'll just run a ground wire down to a grounding pole.

 

[Titanium]

Doesn't matter the direction that the signal travels to reach the antenna. The metal roof will interact with the phasing of the signals if it is nearby.

 

[Troch77]

Doesn't matter the direction that the signal travels to reach the antenna. The metal roof will interact with the phasing of the signals if it is nearby.

What would you recommend?
It will only be about 3 feet above, and 1 foot out over the over hang.

I don't want to turn it into a lightning rod lol.
Thats already going to be 35 feet high.
But Ive tried other antennas at 10 feet with no success, 20 feet with some success I figured 30 -35 feet would work.

 

[Titanium]

I would mount it much higher (6/8/10 ft). As you aim the antenna pay close attention to the quality readings on all channels. Small changes in the antenna positioning near a metal roof or siding will have a major effect on reception. Might attenuate some frequencies and boost others.

Note that the metal roof might actually improve reception depending on how it interacts with the antenna and the signals. Every install is different and it is impossible to predict with certainty due to so many variables... Typically, the higher the better, but I have some signals that come in best with the antenna near the ground and lose them when higher.