Roof-mounted antennas and lightening strikes

comfortably_numb

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So after my recent lightning strike, which fried the power supply of my Dinova Boss Mix antenna, I've found myself pondering how to prevent this from happening going forward. The Dinova has two rabbit ear side-lobes that can be recessed into the plastic casing of the antenna. Would it be wise to recess those to help prevent another direct hit?

Alternately, the Diginova Boss antenna (the Dinova's predecessor) has no rabbit ears at all; it's all plastic. Would this be an even better alternative? Since plastic isn't a conductor, I'm hoping changing to something all-plastic might help reduce these strikes (I've experienced at least 3 over the years).
 

primestar31

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There's next to nothing you can do about actual strikes if your location is unfortunately one of the susceptible places. By FAR the best thing, is to ground the coax line directly to the house ground stake with a proper coax ground block. IF you used a metal pole to put it up, you need to ground that also. This article below explains WHY. (It ain't just lightning you should worry about)

TV Antenna Grounding

IF the coax and mast is grounded, the ANTENNA is grounded. So nothing special is needed other than that. (except prayer)
 
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comfortably_numb

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There's next to nothing you can do about actual strikes if your location is unfortunately one of the susceptible places. By FAR the best thing, is to ground the coax line directly to the house ground stake with a proper coax ground block. IF you used a metal pole to put it up, you need to ground that also. This article below explains WHY. (It ain't just lightning you should worry about)

TV Antenna Grounding

IF the coax and mast is grounded, the ANTENNA is grounded. So nothing special is needed other than that. (except prayer)
The mast and pole are grounded, and the coax out of the antenna is ran through a ground block. So even if the antenna is all-plastic, that's not any better than an all-aluminum yagi?
 

primestar31

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The mast and pole are grounded, and the coax out of the antenna is ran through a ground block. So even if the antenna is all-plastic, that's not any better than an all-aluminum yagi?
How could a plastic antenna work? Plastic isn't electrically conductive, and you need conduction for RF waves. They probably have some tiny metal parts in them that do the actual reception, and just feed their sales blurbs with B.S. Or the plastic has metal embedded in it somehow.

Is the ground block grounded directly to house ground with a short wire heavy gauge COPPER wire? The thicker the wire you can use, the better! I use 6 gauge for my antenna and mast grounding.

Consider this: setup a REAL lightning rod on the opposite end of your building, fully grounded with it's own ground stake and such. Use a really good copper ground rod, the longest you can find. Hardware stores sell them, and a sledgehammer will drive them. Some pails of water can help soften ground and make it more conductive. Make THAT the more likely target, instead of your antenna system.
 
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comfortably_numb

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How could a plastic antenna work? Plastic isn't electrically conductive, and you need conduction for RF waves. They probably have some tiny metal parts in them that do the actual reception, and just feed their sales blurbs with B.S. Or the plastic has metal embedded in it somehow.
The Dinova Boss Mix is completely encased in plastic (except for the rabbit ear lobes on either side)

Yes, we have a large ground rod with copper ran to the block
 

primestar31

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The Dinova Boss Mix is completely encased in plastic (except for the rabbit ear lobes on either side)

Yes, we have a large ground rod with copper ran to the block
So, it likely only picked up a ground pulse from a nearby lightning strike. All you can do is all of the above, and hope. Lightning is a VERY strange animal, and is capable of anything. I've seen it destroy everything electronic in a house, and I've seen a direct strike on a house that only destroyed the dishwasher timer! (I was an appliance repair person right out of high school for 3 years)

I've looked at these before, and thought about it, but have never actually tried one as of yet: Aska

They are available at Hypers web site at a very reasonable price with free shipping: Accessories-FTA Satellite Equipment
 
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comfortably_numb

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So, it likely only picked up a ground pulse from a nearby lightning strike. All you can do is all of the above, and hope. Lightning is a VERY strange animal, and is capable of anything. I've seen it destroy everything electronic in a house, and I've seen a direct strike on a house that only destroyed the dishwasher timer! (I was an appliance repair person right out of high school for 3 years)

I've looked at these before, and thought about it, but have never actually tried one as of yet: Aska

They are available at Hypers web site at a very reasonable price with free shipping: Accessories-FTA Satellite Equipment
Is there any signal loss on one of those? Would you place it in-line before or after the ground block?
 

primestar31

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Is there any signal loss on one of those? Would you place it in-line before or after the ground block?
I do not know, you'll have to do a bit of research as I haven't looked at them for years. IF it follows general convention, ALWAYS figure .5db loss on any connection minimum. As for me, I'd put it right AFTER the ground block, and then connect the incoming coax on it's backside.

It sure beats replacing fried equipment.

P.S. Have you REALLY looked over the "house ground" rod, and made SURE it looks proper? Is the main electrical box REALLY grounded to it properly? One house we bought, I dug mine up (copper ground rod) on purpose to check (we were having weird stuff happening to electronics) and it turned out the wire going into the house electrical panel WASN'T CONNECTED TO THE ACTUAL ROD! I fixed that quickly. Scraped it all well with a file, and cranked it down onto the rod within an inch of its life. Be aware that can possible be a dangerous operation, depending on potentials at that moment. In my case, I could turn off the house main as it was a single family.
 

harshness

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Is there any signal loss on one of those? Would you place it in-line before or after the ground block?
Any time you pass through some sort of passive device, there is at least a 0.5dB "insertion loss" introduced by the connectors in and out of the device.

As Mike has pointed out several times, there is little practical you can do about lightning outside of prayer to protect a roof-top antenna from a lightning strike.

You may have some success with adding an even more attractive sink such as a much taller lightning rod with an enormous ground strap, but there's no guarantee. Even if the lightning bolt picked the lighting rod, there would surely be some collateral damage.

The ground blocks that we all refer to (officially known as an Antenna Discharge Unit) are there uniquely to draw off static electricity generated voltages and offer little protection from a 100,000,000V lightning bolt. That much voltage will find multiple paths to earth. Lightning has already gone through hundreds of feet of more or less dielectric air to get to you roof so you're not really going to slow its roll.

Lightning will pass easily through the plastic shell, so it offers negligible protection with respect to lightning.
 

bcw

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NFPA 780 Standard for the Installation of Lightning Protection Systems. If you wish to know as much as you think you do.
 
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harshness

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NFPA 780 Standard for the Installation of Lightning Protection Systems. If you wish to know as much as you think you do.
The National Electrical Code (NEC -- also from the National Fire Protection Association) is typically the applicable code cited by building codes departments of jurisdictions relative to homes.
NFPA 780 mission statement said:
NFPA 780 provides lightning protection system installation requirements to safeguard people and property from fire risk and related hazards associated with lightning exposure.
The issue here is more about the protection of sensitive electronics from damage.

That may be like using a fire hose to clean the dust out of your receiver.
 

bcw

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The National Electrical Code (NEC -- also from the National Fire Protection Association) is typically the applicable code cited by building codes departments of jurisdictions relative to homes.The issue here is more about the protection of sensitive electronics from damage.

That may be like using a fire hose to clean the dust out of your receiver.
As usual, if the ref does not reflect your view it is of no use.
 

bcw

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Nor is it of any use if it isn't applied (or doesn't apply) to the topic of the discussion.
It's fairly short, why don't you read it, it does have a section on antennas and masts. But you already know everything so why bother.
 

harshness

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It's fairly short, why don't you read it, it does have a section on antennas and masts.
As you are the one that claims the information will be useful and that you know better than I, it seems like the details of how what you propose is going to save comfortably_numb's various devices from ruin should come from you.

Since the information isn't readily available to the general public (at the least, it requires registration on a website), it is the least you could do to demonstrate that you have a useful recommendation.
 

bcw

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As you are the one that claims the information will be useful and that you know better than I, it seems like the details of how what you propose is going to save comfortably_numb's various devices from ruin should come from you.

Since the information isn't readily available to the general public (at the least, it requires registration on a website), it is the least you could do to back up your assertions.
Since you are an expert I will leave that up to you, I just wanted for you to have accurate and up to date information rather than hearsay. You might try a library.
 

primestar31

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Come on BCW, enough of the BS, you should know better. Stop ruining CN's thread with petty squabbling. Harsh is HARSH, but he's always consistent, and he does give some good info. Just like any of the rest of us, (including you) and sometimes better, maybe sometimes worse. Let it go.

I gave plenty of information above, and all an average person can do is all of that, and then HOPE. Just like all the rest of us have ever done since electronics has existed.

IF CN wants to spend far more money hiring a professional to do all the work your solution would take to get hardly any better results above luck and prayer, that's HIS choice.
 

comfortably_numb

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IF CN wants to spend far more money hiring a professional to do all the work your solution would take to get hardly any better results above luck and prayer, that's HIS choice.
Based on all the excellent suggestions posted here, I think I'm covered as well as I can be. Large ground rod is in place, heavy gauge copper connects the ground rod to the ground block. Coax from antenna is connected to ground block. Copper lead runs from the J-pole to the ground block. Now the mount and the antenna are grounded as well as can be.

Luckily, it seems to me that these preamps and their power supplies sort of act as a buffer between lightning reaching my components, so hopefully all I'd ever have to replace is a preamp if I'm ever struck again. I'm keeping an extra preamp on the shelf in case this happens again.
 
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primestar31

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Did you clean the connection points really well between wires and what they are bolted to? Such as scraping/filing/sandpappering off a little paint on the J-pole to get to the bare metal?

The better the connection, the lower the potential. Might not be by much, but hey, it's not much more work.
 
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jayn_j

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grounding is such a complex issue that a lot of factors will affect its effectiveness. Moisture in the soil, sand vs clay vs rock, proximity to other ground loads, etc.

I have a friend who put himself through college as a phone installer. One day he was providing service to a new home. He drove in a 6 foot copper rod and took a hit he later measured at over 400VAC when he tried to tie the phone gnd to it. Turned out the house was adjacent to a power substation and the grounding for the transformers had saturated the soil near the transformers.

You can kill electronics with very small signals, like 20V or so if not properly protected. That doesn't require a direct strike. As Mike mentioned, there really isn't much you can do about a direct strike and it is tough to predict how the current from it will actually flow.

The purpose of a lightning rod is to bleed off atmospheric charge BEFORE it builds to the point of an actual lightning strike. Mike's suggestion about a dedicated lightning rod nearby, but not too close is a good one. Try to bleed the charge and let the lightning find another path to set its arc.

CN has a style that often annoys me as well, but he is spot on about insertion loss here. It is impossible to overground. In addition to the grounding block on the coax, you need to ground the antenna with a heavy copper ground strap.
 

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