Spark Gap (1 Viewer)

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tracker1998

SatelliteGuys Pro
Apr 6, 2008
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I have a few towers and dishes not grounded.
Some say that ground attracts.
Some say that ground rejects.
All to do with lightining and such.
Others say your system may have problems if not grounded?

I would like to hear from all of you on your thoughts!
Thought it may be an interesting thread?
N.B. keep a "spark gap" in mind as well!!



tracker
 
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drboyddrboyd

SatelliteGuys Family
Jan 4, 2010
115
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US
Your system is ever-so-slightly more likely to be hit by lightning if grounded. However, if an ungrounded system gets hit, then the lightning has no place to go except down the antenna lead into your house. The chances of it starting your house on fire are essentially zero if properly grounded. If it's not grounded, rotsa ruck.

I have a few towers and dishes not grounded.
Some say that ground attracts.
Some say that ground rejects.
All to do with lightning and such.
Others say your system may have problems if not grounded?

I would like to hear from all of you on your thoughts!
Thought it may be an interesting thread?
N.B. keep a "spark gap" in mind as well!!



tracker
 

tracker1998

SatelliteGuys Pro
Apr 6, 2008
166
0
Sometimes lighting goes up sometimes down?
Thread open for this topic.
Thanks for the reply.
Ground or not???
 

drboyddrboyd

SatelliteGuys Family
Jan 4, 2010
115
0
US
Lightning goes between - it won't matter to your house if it's going up or down.

Ground!

The National Electric Code says to ground; there's always a remote chance your insurance company could say, "Oh, you made a change to your house that was dangerous - sorry!" if you don't ground.

Sometimes lighting goes up sometimes down?
Thread open for this topic.
Thanks for the reply.
Ground or not???
 

Cadsulfide

SatelliteGuys Pro
Sep 8, 2008
1,305
0
Cavalier, North Dakota
Grounding IS a big deal, lightning and accidental crosses with the AC power lines CAN happen. Static charge can build up on ungrounded conductors (antenna's, etc) to the point of frying your equipment. Ground blocks are only $1 or so each, they also make good test points in your system.
 

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
1
Western Maine
Re the question of whether grounding attracts or rejects, I assume this refers to lightning. In MY opinion, there is no question that grounding a tower or (if it were possible) to ground a dish, that it would make a lightning strike LESS not more likely. This is because the likelihood of a lightning strike is usually dependent on two things, the difference in voltage between the cloud and tower, and the distance between the cloud and tower. These two things basically end up giving a volts per inch type gradient, that will end up determining whether the breakdown point of the air has been exceeded, ie the lightning strike won't occur until the air kind of breaks down and becomes conductive. Grounding will effectively cut the voltage differential in half, because when a highly positive _OR_ negative cloud passes over, the poorly conductive soil surface will become polarized to the opposite charge. Ie when the tower is grounded, the tower will be at zero potential vs say the +V potential of the cloud, whereas an ungrounded tower will effectively be -V vs the +V potential, so the voltage difference will be 2V instead of 1V. People talk about giving the lightning a path to ground, which is an issue once the strike has started, but relative to the odds of having a strike, grounding will make the strike less likely, because it keeps the tower at zero potential rather than developing a polarized charge opposite to that of the cloud.

However, that is only part of the problem. Other important issues are (1) protecting your house from burning down if there IS a strike, (2) protecting your electronic equipment not from a strike, but from the large static charges the build up prior to a strike, and (3) protecting your equipment from voltage differences that develop between the ground out at the dish vs the ground in your house, and (4) the question of if you ground, WHERE do you ground.

The NEC is mainly concerned with protecting your house, not your electronics, and is thus mainly concerned with dissipating a lightning strike once it has occurred. While logical, it may or may not protect your electronics, depending upon how it is interpreted.

The NEC is pretty clear that any antenna system such as a dish or TV antenna should be grounded at your service ground where the power comes into your house. Ie this is NOT what some people do, ie trying to actually ground the dish itself. While I think grounding the dish itself might make a strike less likely, unless it is done properly, which involves HUGE grounding straps that connect the dish ground to the house ground, which for most installations might cost thousands of $s, would make things worse than not grounding the dish at all. Basically you could end up with a different ground potential out at the dish compared to what you have in the house, and this can end up causing all sorts of issues when you have an lnb whose ground might be greatly different from the ground of the receiver. Basically, it's better to ground the shield of the coax where it enters your house, and this should be done via the house service ground.

The problems come up with situations where there is no convenient way to route the coax so that it enters the house near the service ground. People tend to bend the rules, and the question is which way of bending the rules is best. I don't recommend doing what I do, so I won't mention how I've bent the rules, but I will say that the ONLY equipment that I've had killed by static discharge have been receivers that were directly or indirectly connected to service grounds that were away from the house. Ie I went for years without a problem, until I let DirecTV do a free "upgrade" to give me local channels. They installed their dish out by the power pole that feeds my house, and they grounded their dish on the power pole ground, instead of at the service ground at the house. I think I lost 4 DTV receivers and one other receiver sitting next to the DTV receiver due to that ground. I've since disconnected their ground block, and haven't had a problem since. During the period that I lost the 4 DTV receivers, I had NO problems with any of my FTA dishes that were ungrounded.

Bottom line..... If you ground, ground to the house service ground, or at least to a solid ground connected to this. Do NOT ground AT your dish with a ground separate from the house ground.

Now, re spark gaps... I really think that these are more useful for open antennas like a TV antenna, where the actual driven element is exposed to the lightning or static charges. I've seen these mostly used for balanced feed lines, like TV twin lead. I also believe that once potentials are great enough for a spark gap to function, you've got enough potential to fry most electronics anyway, so it's mainly a way of protecting your house.
Since the driven element of your sat system is enclosed within the grounded case of your LNB, I don't see any convenent way to use a spark gap here, unless it is between the shield and some ground.

Just my opinion, which I've given many times, and each time I've received lots of opposing opinions, and I don't expect many to agree,...... but you asked for opinions. :)
 

ynnedibanez

SatelliteGuys Pro
Dec 7, 2009
536
58
Greeneville, Tennessee
the ground is also a path for stray electrons.
be it static electricity, or problems with wiring, or whatever else, it is a way to dispose of problematic charges before they do damage like shock someone, or fry a cmos chip or something.
 

McGuyver

SatelliteGuys Pro
Apr 4, 2007
783
0
Nuclear Testing Grounds
All excellent replies! I, an ex-industrial electrician say to ground it all. Everything should be grounded to prevent static discharge even if lightning was not a threat. I've seen propane tankers explode because of a faulty ground cable at the loading rack and people died as a result. We may not be talking about serious injury or death here but definately serious damage to equipment that is sensative to static discharge.
 

pedrogarcia

SatelliteGuys Pro
Dec 27, 2008
630
1
Kalamazoo / Limassol
All excellent replies! I, an ex-industrial electrician say to ground it all. Everything should be grounded to prevent static discharge even if lightning was not a threat. I've seen propane tankers explode because of a faulty ground cable at the loading rack and people died as a result. We may not be talking about serious injury or death here but definately serious damage to equipment that is sensative to static discharge.

I agree. Just one small point remote towers should be grounded locally cable size to code. There is no need to run a cable back to house ground. That way there will be no ground loop impedance problems. Remember the coax shield to virtually all fixed dishes does not ground the dish as the LNB is normally plastic mounted. If a motor is involved there will be a ground path back.
The actual codes are currently being looked at for amendment along these lines
 

tracker1998

SatelliteGuys Pro
Apr 6, 2008
166
0
Yes McGuyver. All good answers indeed !
I was curious if a "spark gap" might be an option as I see they sell them for homes at Home Depot? Good read B.J.

If anyone has more input on the subject, please share your thoughts !

tracker
 

SatelliteAV

SatelliteGuys Master
Lifetime Supporter
Sep 3, 2004
6,486
183
Roseville, CA
I agree. Just one small point remote towers should be grounded locally cable size to code. There is no need to run a cable back to house ground. That way there will be no ground loop impedance problems. Remember the coax shield to virtually all fixed dishes does not ground the dish as the LNB is normally plastic mounted. If a motor is involved there will be a ground path back.
The actual codes are currently being looked at for amendment along these lines

It is never safe to have multiple grounds without bonding them together.

To clarify pedrogarcia's post.... if there is any connection between the coax and the mast/tower, the mast/tower must be bonded to the structure's ground to avoid a voltage potential. I have observed improper installations where the technician mounted a ground block or a switch to a grounded mast/tower, but neglected to bond the mast/tower to the structure's ground.

Failure to bond a locally grounded mast/tower creates a potentially lethal voltage potential. If a technician was to working at a home with wiring issues he could be in holding a coax cable and be electrocuted when touching the locally grounded mast/tower.

I have been shocked a few times and blown up several receivers while working in homes with improper wiring hidden behind the walls. In a perfectly wired world I agree with pedrogarcia's post. Unfortunately.... we don't, so ground and bond!
 

ynnedibanez

SatelliteGuys Pro
Dec 7, 2009
536
58
Greeneville, Tennessee
It is never safe to have multiple grounds without bonding them together.

To clarify pedrogarcia's post.... if there is any connection between the coax and the mast/tower, the mast/tower must be bonded to the structure's ground to avoid a voltage potential. I have observed improper installations where the technician mounted a ground block or a switch to a grounded mast/tower, but neglected to bond the mast/tower to the structure's ground.

Failure to bond a locally grounded mast/tower creates a potentially lethal voltage potential. If a technician was to working at a home with wiring issues he could be in holding a coax cable and be electrocuted when touching the locally grounded mast/tower.

I have been shocked a few times and blown up several receivers while working in homes with improper wiring hidden behind the walls. In a perfectly wired world I agree with pedrogarcia's post. Unfortunately.... we don't, so ground and bond!

+1:up
 

Ironsides

SatelliteGuys Pro
Dec 4, 2008
319
0
North Carolina
ARRL

The ARRL is a good resource for learning how to properly ground your equipment. They have good articles on how to ground towers and antennas. I feel very firmly about proper grounding because it could save your life or your home. It protects your loved ones!

Something I've learned being a Ham Operator is very few satellite antennas or radio antennas are hit by direct hits, most of the time it's the static from the lightening that causes the damages. Direct hits are going to cause problems even with good grounds but it gives it some place to go rather than your lazyboy.

Personally I don't think grounding your equipment is going to raise your chances of being hit. I think its going to raise your chances of being protected in the event a strike or nearby discharge does happen.

Another Myth that has been told to Dish owners for as long as I have been involved with Satellite/Amateur Radio is the Mounting Pole provides a good ground. That might be true if the Mounting Pole wasn't encased in cement. It would also have to be in the ground at least 4 feet! Cement acts as an insulator and prevents the mounting pole to make a good ground.

20 some odd years ago when I had my 1st C-Band dish installed, we went the extra mile grounding. It was money well spent in my opinion, due to the fact that several dishes in my area most all have experienced problems with lightening static during the summer.

We used 2 ground blocks at the LNBf, that grounds again too the Scalar and again down each mounting arm 4 in total. All those are tied back too the centre of the dish and grounds again. Another ground comes from the dish mover and ties back to the ground hub. That hub connects too 4 8' grounding rods placed at 12 o'clock, 3, 6 and 9 around the main mounting pipe. All 4 of those ground rods are connected together and tie back to the main mounting pipe. Basically the entire dish is grounded using this method...It might not be the best grounding method but I can say it's worked for over 20 years. My receivers and transmitters are all grounded to ground hubs made from copper bars. The hubs are tied to 8' ground rods outside my home at 2 different points due to the location of all my junk. My electrical box had 1 4 foot ground rod placed there by the electrical company, I installed 2 more 8 foot ground rods and tied them to each other.
 
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GrumpyGuy

SatelliteGuys Pro
Jun 17, 2006
249
0
Northeast Ohio
It might be worth pointing out that concrete is actually a better conductor than most soils. The [ame="http://en.wikipedia.org/wiki/Ufer_Ground"]Ufer Ground - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Nuvola_apps_ksim.png" class="image"><img alt="Stub icon" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Nuvola_apps_ksim.png/30px-Nuvola_apps_ksim.png"@@AMEPARAM@@commons/thumb/8/8d/Nuvola_apps_ksim.png/30px-Nuvola_apps_ksim.png[/ame] system takes advantage of this phenomena by utilizing the steel rebar within a concrete footer as a ground. I've used this technique with good results.

I'm no expert regarding the N.E.C., but as recently as 2002 a Ufer ground was an approved supplemental ground for situations in which traditional grounding techniques failed to achieve sufficient conductivity.

It is however my understanding that more recent versions of the N.E.C. derate the Ufer. I don't understand why, but will offer my speculation that it has to do with hazards to personal performing demolition or renovations which involve cutting of the rebar used as part of a Ufer, and/or the likelihood that such renovations would be completed in a way that would not restore effective grounding.
 

McGuyver

SatelliteGuys Pro
Apr 4, 2007
783
0
Nuclear Testing Grounds
It might be worth pointing out that concrete is actually a better conductor than most soils. The Ufer Ground system takes advantage of this phenomena by utilizing the steel rebar within a concrete footer as a ground. I've used this technique with good results.

I'm no expert regarding the N.E.C., but as recently as 2002 a Ufer ground was an approved supplemental ground for situations in which traditional grounding techniques failed to achieve sufficient conductivity.

It is however my understanding that more recent versions of the N.E.C. derate the Ufer. I don't understand why, but will offer my speculation that it has to do with hazards to personal performing demolition or renovations which involve cutting of the rebar used as part of a Ufer, and/or the likelihood that such renovations would be completed in a way that would not restore effective grounding.

That's a good point Grumps, I recall grounding cables to rebar prior to the concrete pouring of slabs although they usually may include the use of multiple ground rods for larger pours. The combination of both concrete and soil grounding is about the best it gets I suppose. In the refinery, we electricians had a routine of pouring a saline solution into certain ground rod locations to enhance conductivity in the soil, this was mostly practiced for the more vulnerable towers and large structures due to possible lightning strikes, especially in the tank farms (fuel storage tanks).
 

Ironsides

SatelliteGuys Pro
Dec 4, 2008
319
0
North Carolina
Doesn't that depend on the mixture?

Doesn't that depend on the mixture of the concrete? I guess it depends on state to state. Wow things have changed a lot in 20 years, we always had to make sure the rebar or pipe was acutally in contact with the soil and at least 4 feet beneath the soil before any cement was used. I was always instructed it depended on the mixture and how much silica was used. Wouldn't it also depend on the moisture content of both concrete and soil. Drying times can vary depending on the pour, some times it could take weeks or months or even years for it to fully dry in that case it would make a good grounding. Once all the moisture is gone it couldn't ground as well. I was also instructed that if the cement had a high volume of silica the cement could act as ceramic and most ceramics are insulators unless they have something added to them. Isn't a difference between Concrete and Cement anyway?

This is very interesting! Learn something new every day and it makes me feel old!
 

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
1
Western Maine
.....
Another Myth that has been told to Dish owners for as long as I have been involved with Satellite/Amateur Radio is the Mounting Pole provides a good ground. That might be true if the Mounting Pole wasn't encased in cement. It would also have to be in the ground at least 4 feet! Cement acts as an insulator and prevents the mounting pole to make a good ground.
.....

It might be worth pointing out that concrete is actually a better conductor than most soils. The Ufer Ground system takes advantage of this phenomena by utilizing the steel rebar within a concrete footer as a ground. I've used this technique with good results.
....

One possible way to determine whether your mounting pole is a good ground, and I am definately not recommending this to others, but I have used the technique for other purposes, is to run a 120V power line out to your dish, and after disconnecting all the wires that go to your receiver or dish movers, etc, run a wire from the hot black power line to a 100W light bulb, and touch the return wire from the light bulb to your pole. If it is a good ground, then the light bulb should light up..... _AND_ worms should start coming to the surface around the pole, ie the "other purpose" I mentioned above. I used to use this technique to collect night crawlers, by just driving a metal rod down a bit into wet soil, and connecting a light bulb using the metal rod as a ground. In dry soil the bulb wouldn't light, but in wet soil, it will light up.
I've never tried this on my own sat dish, and I have no idea of whether or not a dish pole could make a reasonable ground or not, but this would be a way to tell. I'm not recommending the technique though, because I think that it could result in someone electrocuting themselves if they didn't know what they were doing. I really suspect that how well any ground works depends more on the soil conditions than it does on how the ground is installed. And even though the above mentioned concrete ground system may work in some situations, that doesn't mean that a pole in concrete will work. If you've ever taken a VOM and tried to get a continuity reading from one part of a pole to another, with some poles, it's hard to get a reading, particularly on a painted or rusted steel pole. Shiny galvanized poles usually keep a good clean surface. I really wonder just how good of contact a painted or rusted steel pole will make with the concrete or soil, even if the concrete or soil is a good conductor.

Also, I agree with Ironsides with respect to that the connections between the pole and the mount, or the mount and the dish or the dish and the feedhorn are all dependent upon how good the connections are between surfaces that often do not have clean metal to metal contact, and if you're really trying to completely ground the thing, virtually every part of the dish has to be bonded to a ground. People who ground those big monster professional commercial or government towers generally bond every section of the tower to a grounding strap, even though the whole thing is metal, because you just can't trust that rusted or painted or corroded metal is going to make good contact.

Basically, I don't think that it is possible to ground a normal mesh bud dish, unless you do something like Ironsides suggests, and most people aren't going to do that. If you don't do that, I think you may be better off without having a ground, or at least without having a ground that is connected at all to the lines running in to your receiver. The smaller metal dishes on a galvanized pole are better, but on the other hand their poles aren't deep enough in the ground to be an effective ground. Bottom line is ground the coax where it enters the house.
 

Corrado

SatelliteGuys Pro
Apr 2, 2007
2,387
275
Hudson Valley Region, NY
A few years ago I had I lightning strike that destroyed all of my equipment. It followed the ungrounded actuator and polarotor wiring into the house. That wiring gets disconnected now whenever a storm is forecast.
 
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1ADAM12

SatelliteGuys Pro
Aug 4, 2009
576
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10-6 Gas Pumps
Ohh u just had to ask

If anyone has more input on the subject, please share your thoughts !

tracker

Firstly, a charged area reaches up from the ground and then a stroke may form from the sky.

A tower is more likely to be struck by a stroke grounded or not.

To prevent a stroke at a point that has a charged area, disapators are used.

A disapator is made up of many hair like threads of stainless steel that is connected to a bonded halo ground system at roof top level of a building or tower.

Another form of a disapator is a tower structure that has an umbrella shape device at the top and what appears to be barbed wire in a cloaking cover. The greater the surface area of disapators the more readily the earth charge is conducted skyward preventing a stroke.

A single earth driven ground rod is of no benefit in parts of the SE USA. A chemical well is drilled deep into the ground and consists of a perferated copper pipe about 4" in dia. and 35' long this is filled with salts, not salt.
Often used at commercial tower sites in Florida. To improve grounding a "Single Point Grounding System" is used. To improve that single point ground five or ten 10' ground rods are driven 10' apart and running away from the tower, all are bonded with 2" wide copper strap buried in the ground.

I could just go on for hours but won't bore you any longer:D
 

McGuyver

SatelliteGuys Pro
Apr 4, 2007
783
0
Nuclear Testing Grounds
I wonder just how much static electricity a mesh reflector could absorb before it discharges? if this is possible then it's likely that it may damage an LNB or cause glitches in the A/V circuits. I used to have an annoying pop sound that blotted out a second of audio when watching a certain channel and always thought it was the network's problem but once I changed some cable configurations, removed or moved some dishes around, the problem disappeared. I had everything grounded properly (I think) but still had the audio glitch that drove me nuts. I often wondered if it could have been an overlooked grounding issue that allowed static discharge to interfere. I can't address it now since the prob is gone.
 
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