Does anyone know of or have some kind off protection for lightning strikes on aerials? I ask because with a lot of expensive kit now connecting to an aerial it would probably be worth while. I already have power and telephone spike protection. Perhaps if your aerial get struck by lightning nothing is going to protect you?

Hi,
I know this does not cover all situations, but because I have many thousands worth of equipment attached, I unplug my antennae main connection during a storm....but to do that you have to be home...
I will also disconnect the electrics as well, although they and the ADSL run through an insured lightning strike arrestor in the form of an UPS
foss

Fossil,

A UPS per se is not a lightning arrestor. A UPS is designed to protect equipment from power distrubances or black out induced system crashes. Some UPS have basic protection in the form of RJ11 or RJ45 sockets with gas arrestors. Usually the outcome of a decent belt from lightning on a UPS is the UPS being killed.
To be completly sure you should fit a dedicated surge device BEFORE the UPS. Let the TVSS product do the surge supression and the UPS do the back up power.
Have you read the fine print on your "insurance". Many of the so called UPS insurance policies I have seen actually exclude lightning.

well my UPS policy includes lightning strikes specifically
I am not saying it will stop lightning, but it has a lifetime lightning damage insurance.
My system runs solely from the UPS and has no physical connection to the power supply...
But here again, I am only referring to my PC and associated setup...not my TV setup...That has surge protection and spike arrestors as well but also gets disconnected...and if storms are predicted and I will be out...all connections are disconnected...
Touch wood, I have only ever had one dead phone...but then again, I am careful
Please don't lecture me...I am not going to state one thing if it says another...and it says that the UPS provides a lifetime insurance against damage causedby lightning strikes to equipment that the UPS runs/provides electricity to
Perhaps I should have left out the word arrestor..
I keep forgetting how minutely every post I write is examined for errors.....despite the fact I said this does not cover all situations and that I also disconnect the power supply during storms.
foss

Yes you can get antenna lightning protection.

I bought one from Dick Smiths recently in the vain hope that an isolation transformer would stop the RF interference my Teac 420 was feeding back in to the antenna loop.

It looks like a fat blue pipe with an antenna plug and socket on either end.

Thanks nospoon - I will check them out. As Foss says - if I am at home, I can disconnect the kit myself. The danger is having expensive gear sitting exposed during a storm when I'm away.

Hi I'm new to some of this stuff

Does anyone know what's good for lightning protection via the telepnoe wires

I read a post over in the Digital TV tuners cards section where a lightning strike damaged the ADSL modem and PC.

Thanks for any help, or if you know where else to look

Some / most UPS's supply a phone line protector...so when you protect the Power you can also protect the ADSL line
But when there is a storm about, which is often and predictable in Qld, I leave nothing connected
foss

Happyeyes,

I haven't come across any 'true' external aerial protection devices.
If there were any lightning arrestor kits available, I assume they should be fitted at the outdoor end. Once struck, you have a time delay or physical buffer along the coax cable before it reaches your indoor devices.

I have repaired 'lightning struck' test equipment which were used for cable TV and I have seen at first hand - vapourised cable sockets including lengths of semi-rigid cables disappear inside the test equipment. With that kind of damage, you are looking at probably thousands of amperes running through.
In my opinion, nothing will stop it...lightning will destroy everything its path to a ground point.

A preventive way is to use an indoor antenna, which I am using.

Pep

Hi Fossil,

I thought I read a post from you saying it was your last and I was so disappointed! Really! I discovered these forums AFTER I purchased a PVR and have learnt heaps, especially why I should have bought a Toppy instead of a Strong 5390 (though after an initial crash and repair, it works like a charm) A HD Toppy will be next on the list!

I assume you are called Fossil because of your age? This reminds me of a line in an old Al Stewart song:

I may be old now in your eyes
But all my years have made me wise!

Your wisdom is really appreciated.

I am probably even older than you, having been using true HiFi gear since the early 60s (courtesy of a HiFi nut Dad and his hand-me-downs, and have been using computers since 1970 in one form or another. I am seriously into home theatre and integrating PC and home ent. systems and am designing a TAFE course around it all that I am running in Feb. this year (Free to boot!!).

I use a sytem for lightning protection that I read in a (very good) book called The Complete PC Upgrade and Maintenance Guide (pp 440 - 450, 4th. ed. Mark Minasi, Sybex) that costs nothing and hasn't failed me yet.

It was designed/invented/suggested by researchers to help protect a few hundred PCs in a building that was regularly hit by lightning, resulting in fried mainboards etc.

He suggests that as lightning is a (DC) force, if you turn it back on itself enough times it will eventually dissipate altogether. His solution is: Tie up to 6 knots in the power cord between the wall socket and whatever is plugged into it. I use short (2m) extension cords running to multi-output powerboards (Kambrroks) for every electrical device in my house, and the same for the phone line to the Modem, and have not had a loss since.

We had some huge electrical storms in my part of the world before Christmas, Telstra lost both my phone lines (ISDN) for a week but I lost no electrical devices at all (apart from the phone and Internet, courtesy of Telstra's inefficency).

Before I discovered and used this method I had lost various items to the demon lightning, since using it - none!

Foss, if you want a copy of the relevant pages of the book (that support your arguments re. UPSs) let me know, I will scan and email them if you want.

My email is davidl@coastal.net.au

Regards,

David

Hi David...and thanks...I have sent you an email
foss

I would strongly suggest investing in a decent contents insurance policy and not worry about antennae shock arrestors or other gimmicks. When it really hits close to home, the damage can come from anywhere. I've experienced a lightning strike at a friends house about 9 months ago. The lightning struck about 30m away from his loungeroom.

There was no damage to any equipment through the power, telephone or antena connections. However, due to the huge EMF surge, the Cat5e networking cables picked up enough juice to fry all connected Ethernet ports in his ADSL modem, wireless router, PC, and XBox. The surge then travelled through the Xbox and fried the video routing board of his home theatre amp, plus the video output stage of his DVD player.

The main culprit was about 10m of coiled up Cat5e on the floor. By leaving the cable in a nice coil, it ended up working like a transformer. Another reason not to neatly coil cabling. Most people stare in disbelief when I tell them that coiled cables are dangerous and that it is much safer to leave them in a mess or have a single large loop. Then I explain the high school physics of electromagnetics to them and remind them of the "battery hooked up to a coil of wire around a nail" school experiment. These days I also tell them the lighning strike story.

Peter,
I remember being told a long time ago,not to coil wires....infact I seem to remember some tags on an extension cable I boughtnot so long ago...however, one good side benefit of this convenient fact is that I have used this reasoning not to keep my masses of wires tidily coiled...lol..so, no wire I have connected anywhere that I can see has a complete coil.
foss

/me looks over his shoulder at the coiled up extension coax cable coming out of his toppy and thinks, hmmmmmmm

Still, its usually not connected into anything, so with luck I'm ok

There is no real protection against lightening strikes only limitations.

If the aerial gets hit, it will be pulverize unless the aerial mast is grounded. That is a problem in most domestic installations including my own where the aerial mast is just mounted onto the fascia board of the roof. (Too much trouble to run a heavy-duty earth wire down, connected to a long iron road hammered into the ground.)

The gap between the antenna proper and the mast is for the lightening strike not existent and the current would run down the earth cable. If on the other hand there is no ground connection, it would run down the coax, cooking everything on its way to find the ground. Even with a proper cable installed, enough energy would hit the tuner to turn up its toes, but at least the house wouldn’t go up in flames.

The solution is to provide the shortest way for lightening to find ground. If your antenna mast is grounded and sticks a meter-o-so above the antenna you did everything you could. All you have to do now is unplug the coax if you hear thunder.

How do I know? The commercial transmitter masts are based on the above.

O, forget about gadgets you can buy and use the money rather to get some heavy earth bride to ground the mast. In many cases a couple-o-length of galvanized water pipe would do the job.

Hammer a 3/8 steal rod into the ground, mount the water pipe on it and to the fascia board with the antenna on top. Now you got a great lightening arrester, worth about 50 bucks.

I have worked some networks and weather stations into some very nasty storm effected areas. Gounding the masts can be one step but to ground out these sorts of currents is impossible without cable more than a 20mm in diameter otherwise it will just vapourize and I have some "nasty" photos of of the damage left after this happens. The skyscrapes in the city have cables up to 50mm in diameter to channel the strike and in some cases have nifty counters to tell you how many times they have been hit. 1 Eagle Place in BrisVegas has this set up and I saw it in about 1999 and it had recorded about 23 strikes. Also grounding can be a simple invitation for the lightning as a simple path to ground.

I have had some very good results with the spike and surge arrestors that you can get form the more reputable companies (look at $100 not $10). They will definitely not protect you from a direct strike nothing but a large airgap will and I am talking metres not cm. Lighting will go anywhere it wants and I have heard of it completely avoiding a large metal tower and strike the ground beside it. It will come down through a house hit the water pipes and then leap off kitchen sinks to other appliances.

Unpluging is the best, next is the spike surge arrestor or UPS and lastly prayer. I like Davidl's idea of knoting the cable and could see that it may help as well and I am going to knot up few things this afternoon.

I can vouch for spike arrestors when an office I looked after was struck by lightning. Spike arrestors were all fried and needed to be replaced but all PCs powered up. The thousands of dollars of recording equipment that wasn't protected never powered on again.

Davidl’s solution is based on a theory which is correct in so far as the lightening charge potential is DC, (the clouds are negative and the ground is positive), but wrong if that DC discharges into the ground. At this instant the discharge current creates an electro magnetic field with a very wide frequency spectrum, inducing energy into anything nearby that has a ‘differential’ potential, (a piece of outstretched wire in comparison to a metal ball). Therefore, as petero pointed out a coiled up coax would be affected but not because it is coiled up but rather because it has a larger (longer) area than a shorter piece. In order for a transformation to take place a coupling into a secondary element is needed whereas in this case resonance absorbs the energy. (Lightning has a very broad frequency spectrum).

Putting knots into a power line is theoretically correct as it would cancel the electromagnetic field and again ‘theoretically’ absorb the energy spike, but in practice that energy spike, which consists of a vast spectrum of spices wouldn’t even notice any knots. And even if those knots would be able to stop any energy traveling along that line that energy would be lower than the ac used to power the equipment. Any ferrite block or ring one can get at DS or Jaycar would do a job many times better than a line full of knots.

It’s a bit like religion, if it makes you feel save put your belief into it.

I definitely use the unplug method, having seen just how ineffective 'commercial' grade protection can really be. This is the least damaged part of an Ericsson mobile phone base station - a DC PSU - after a near to, not direct, strike to the tower. Now imagine how your PC / TV / PVR with comparatively weak protection would have managed...

Wow! Thanks for the fantastic responses. Perhaps I should check my home contents insurance and possibly get an internal aerial.

This links is one of my favouite videos, the power grid is being 'crossed over'

http://www.big-boys.com/articles/powerwire.html

As you see the HV sparks are dancing around in the air looking for a path to connect to. Don't think any protection devices will guard this...

Pep

This power arc at a substation is very different from that of a lightening strike. The former is a normal event in the process of disconnecting 100- or 200 thousand volt AC on a humid day. Lightening on the other hand is building up millions of volt DC between the clouds and the ground until a path is found from a higher cloud to the next one below which has a lesser charge. At that point the higher cloud fires, which heats up the air to such a temperature that it creates an ionizing path (a virtual short circuit or in other words a wire). Now the cloud below is charged up to that of the top cloud potential and fires down to the next one below and so on until the strike hits the ground. That all happens as chain reaction within a couple of seconds.

If you analyze the above you will also understand why a strike doesn’t come straight down but rather jumps from one cloud to the next, attracting strikes from other clouds before it decides to hit the ground. The thunder you hear is created by the ionization of the air which forces a path faster than the speed of sound, a kind of bum a fighter jet creates.

To understand what goes on within a lightning strike let’s cut a slice out of it, do the same with a tree trunk and compare it. Every ring in a tree trunk would represent a different voltage. The center logically has the highest- and the outer rings have the lowest voltage. Now consider that the whole thing has a diameter of infinity, meaning that the voltage difference between the center and the outer rings is infinite. Consider further that if the core is at a million volts, what would the voltage be 10…..100 and-so-on-meters from the core. Now let’s say you are standing around with your arms stretched out, (if you are bored in a thunderstorm of cause) with one hand pointing to the spot the lightning strikes, what would the voltage difference be between your two hands? If you decide that there is a difference, then we can assume that a current will flow from your ‘hot hand to your ‘cold hand’, knocking you ass-over-head. The thunder, which is created by the air rush faster than sound will strip off your close and may just left you standing in your boots. All that if you aren’t hit but just tickled.

I suggest using this theoretical scenario if you are trying to lightening harden your crib but if that is too difficult, knot up your cables instead.

How much is your budget for lightning protection?

http://www.lpi.com.au/

http://www.iceweb.com.au/Surge+Lightning/Surge+lightning.htm