Grounding antenna that is away from house

[harshness]

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.

Read the first paragraph of this Wikipedia article carefully:

https://en.wikipedia.org/wiki/Lightning_rod

Pay special attention to the sentence that includes the word "preferentially". That means that if it is going to happen, you prefer that it strike your lightning rod system. You're essentially making your lightning rod more "attractive" than what it is protecting.

Whether an antenna is a lightning rod or not, if it is hit, there will be extreme voltage on the coax so the best you can hope for is to reduce the chances of the antenna being hit. To that end, you don't want to make a lightning rod out of the antenna.

 

[Troch77]

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.

Now what do I need as far as Lightning protection.
A Surge Arrester?
With 8 Gauge ground wire and ground rod?

Remember my Antenna is 30-35 feet from the ground.
My coax run might be a little longer but I bet its close to the same distance.

 

[Titanium]

Is the antenna installed near the structure utility ground rod? If so, use it to ground the mast and install a ground block before the coax enters the structure. 8 gauge is likely more than adequate and typically see 10/12 gauge used.

According to NEC (National Electrical Code). If the utility ground is not near the antenna location, drive a ground rod, run an appropriate gauge ground wire from the mast and install a ground block before the coax enters the structure. Connect a bonding wire between the ground rod and structure ground. The wire gauge is calculated on length of wire. A surge arrestor is optional but a good idea if you are in a region with frequent storms.

 

[Troch77]

Is the antenna installed near the structure utility ground rod? If so, use it to ground the mast and install a ground block before the coax enters the structure. 8 gauge is likely more than adequate and typically see 10/12 gauge used.

According to NEC (National Electrical Code). If the utility ground is not near the antenna location, drive a ground rod, run an appropriate gauge ground wire from the mast and install a ground block before the coax enters the structure. Connect a bonding wire between the ground rod and structure ground. The wire gauge is calculated on length of wire. A surge arrestor is optional but a good idea if you are in a region with frequent storms.

The utility ground rod is essentially straight down.
So thats no problem.

Now what kind of Ground block?
Can you post a link or show me exactly which kind or type? Please.

Its just going straight to the Hopper3, so there will be no splitters
I just want to make sure, my house doesn't burn down or blow apart my Hopper if a nearby strike happened.

 

[Titanium]

This is the type I use. Good quality with rubber boots to help protect the fittings.
http://www.ebay.com/itm/Brand-New-P...-and-Cable-Approved-with-Rubber-/252711891014

Put a dab of dielectric silicone in each fitting before installing to protect from water intrusion and corrosion. A few wraps of amalgamated rubber tape over the f-fitting will give a great water resistant seal and easy to remove without sticky residue.

 

[Troch77]

This is the type I use. Good quality with rubber boots to help protect the fittings.
http://www.ebay.com/itm/Brand-New-P...-and-Cable-Approved-with-Rubber-/252711891014

Put a dab of dielectric silicone in each fitting before installing to protect from water intrusion and corrosion. A few wraps of amalgamated rubber tape over the f-fitting will give a great water resistant seal and easy to remove without sticky residue.

Thanks a lot , I'll let you know the end results.
And I still have to complete my FTA dish as well.
So I'll be back.
Thanks again.

 

[jstoddard]

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.

If I'm following you, you're saying that if a ground the antenna to earth at the top of the canyon, and use a grounding block at the house (which is about 70 feet away) that it will store voltage in the line, which could be dangerous? So are you saying I need to run a copper ground all the way from the antenna down to the house? If I don't do that, should I only ground at the antenna and not at the house? At one point in time, there were probably 20 antennas up on the canyon rim (back before satellite dishes) I doubt many of those folks grounded anywhere but at the antenna. But I want to be safe. Thanks.

 

[Titanium]

There are two issues in play. 1. Lightning countermeasures. 2. Voltage potential. The antenna needs to have short path to an excellent ground with low resistance to deal with lightning and the grounding points need to be tied together in order to be balanced to minimize and equally disperse the EMP.

Voltage potential is not stored in the coax, but the differential between multiple grounding points will attempt to equalize by moving between the grounds. If the coax is the route with least resistance, it becomes the path for equalizing. If no ground connection is made to the structure ground prior to entering the home, voltages from electrical events and/or potentials may pass through you or your electronics while moving towards or away from structure ground. It should be noted that voltage potentials are a major cause of failed HDMI ports as this is typically the weakest link between components.

Remember having to connect a grounding wire between the phonograph player and the amplifier to prevent a hum in the audio? This is an example of voltage potential being provided a better path to ground rather than passing through the high impedence audio connectors. The humming sound is the audio caused by the voltage flow.

Yes, the ground rod at the top of the canyon needs to be bonded to the structure ground to eliminate this voltage potential from traveling through the distribution and possibly your electronics in an attempt to equalize.

If your not into deciphering the NEC handbook, a very good informative book on grounding and bonding is "The Grounds for Lightning Protection" published by Polyphaser. Here is a link to an online version for communication sites. http://www.radio2way.net/Polyphaser Guide.pdf

 

[. Raine]

What Titanium said about potential in the ground changing with seasons and dampness of the ground is very true and something to keep in mind when checking for voltage potentials of that sort. Just because there's none when it's checked at one particular time doesn't mean there won't be any at a later date when the ground is damper.

A while back I and my daughter made a simple earth battery by pounding a copper rod into the ground and then burying a zinc plate a few hundred feet away. The voltage potential when the ground is dry is about half a volt, when it's damp, it climbs higher. The orientation to the earth's magnetic field makes a difference too and some areas also have natural telluric currents in the ground.

Voltage potentials from the ground can vary drastically from many different factors.

 

[harshness]

There is a certain failing in the idea that you can use a ground wire big enough to sap a lightning strike. A typical lightning bolt represents 200,000 to 500,000 volts and it is estimated that there can be up to 1 terawatt of discharge. If lightning strikes something, it is going to follow all paths at relatively high voltages. Coaxial cable is one such path that is a relatively good conductor. Another fallacy is that lightning is just one bolt that lasts for a very short time. It is actually many shorter bolts following an established path. You have to think about what happens after the main ground vaporizes.

Here's a pretty good backgrounder on the subject of lightning strikes:

http://www.aharfield.co.uk/lightning-protection-services/about-lightning

. Raine's offspring's observation that running such a grounding scenario (especially with different elevations) will cause a current loop is not to be ignored either. Electrolysis is not our friend in setting up a reliable grounding system.

Finally, coax grounding blocks are really just there to sink small voltages that result from wind-induced static electricity and elevation differences. They aren't much protection from voltages sent down the line (as evidenced by the fact that they carry the DC voltages added by Power Inserters).

 

[Titanium]

Bonding multiple grounding points eliminates voltage potential (current loop?), bonding doesn't create it.

Please elaborate on how elevation differences increases voltage potential. Ground potentials are affected by soil conductivity. Does electricity flow better downhill? LOL

 

[jayn_j]

I stopped responding to avoid this sort of pissing contest with harshness.

Unfortunately, a good book has been ignored in favor of a wikipedia article and some guy in the UK trying to sell stuff. Again, I encourage you to look at this reference, put together by experts and published by the IEEE.
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

Here is an interesting quote on distributed grounds:

Most new houses are built with power, phone, and CATV entry points close to one another. That is very desirable, and makes it easy to mount the AC protectors and signal protectors close to the main building ground point (Figure 4). If wiring comes into a building at many different points, it is much more difficult to get proper protection against lightning surges. Even if surge protectors are installed at these alternate entry points, the long ground wires running back to the main building ground greatly reduce the effectiveness of the protectors. In highlightning areas, where lightning protection is a major concern, it is worth routing as many AC and signal cables as possible past the building power entry point, to facilitate good grounding for protectors and cable sheaths.
The coaxial cables carrying CATV signals and small-dish (DBS) satellite signals are often the path for damaging lightning surges to enter the building. For CATV cables, the code-required bonding of the sheath to the building ground is frequently omitted. For the satellite systems, the NEC/CEC require bonding of the antenna mounting hardware, as well as the incoming cable sheath, to the building ground. This is often difficult to do. If the incoming CATV or antenna lines can be routed to a distribution closet near the AC service entry point, the required bonding can be achieved.

This basically supports the need to tie grounds together with sufficient gauge wire to prevent this sort of thing.

As for lightning rods attracting lightning
Why would anyone ever erect such a thing if it worked like you stated? A lightning rod is designed to bleed off a potential EMF source BEFORE it build to the level of a full lightning strike. Yes, you see 'lightning" flash, but it is at a much lower level than a full strike. This is considered a desirable thing.

Absolutely nothing will protect from a full strike. A full strike will overwhelm the local ground and then go searching for other paths to bleed off the charge. Generally your TV, electrical circuits, and anything else that might provide a path to a lower potential ('ground')

 

[jstoddard]

Thanks again. I think I'm beginning to get it. The mechanics are a little daunting. The canyon is extremely rocky. There is no way to bury either the coaxial cable or a bonding wire, so both would have to be laid on the top of the ground. Not sure of the ramifications of that. Enclosing in plastic pipe isn't really feasible either, both from an expense and aesthetic angle.

 

[Titanium]

If the coax cannot go aerial and will lay exposed on top of the ground, definitely go with direct burial type cable. This coax type has a heavier pvc UV resistant cover and a sealer that will heal any punctures. No harm in laying a bonding wire alongside.

You might also consider placing standard Rg6 or RG11 along with a bonding wire in black irrigation tube sold various diameters in coils. This would provide very good protection and last for years.

 

[jstoddard]

Thanks! I'll look for that.

 

[harshness]

Why would anyone ever erect such a thing if it worked like you stated?

If you have something that you don't want to be attacked, you present the opponent with an irresistible sacrificial target. To lightning, the best target is the one that presents the least resistance in the path to ground. The thunderclouds are committed to equalizing by arcing to the ground beneath them and if you present a shortcut, it will likely follow it. We call this a lightning rod.

At the point of a lightning strike, we're not talking about stray voltages or currents. Current requires a circuit and unless your lightning rod touches the thunderclouds, its not equalizing those cloud voltages harmlessly to ground.