Lighting protection for TV antennas?

**Pray.

Seriously, there is not much you can do. When my antenna guy put mine up, he offered me lightning protection. For $150.00, I figured it was cheap insurance. He put a 7mm diameter aluminium cable from the mast to ground. It probably doesn't work, but it is probably better than nothing. In 30 years, I've not had a problem, but that proves very little.

--
Trevor Wilson
www.rageaudio.com.au

The paranoid disconnect the cable from the wall.

Dave :)

The answer is simple!

Install a 30mm steel pipe in the ground next to your house, just make sure it's 3m higher than your antenna and at least 2m underground.

Of course, this may attract more lightning than you usually have hit your aerial...

-mark

"Poxy" wrote The subject says it all - is this something that is often/ever done?

**** I have never seen any TV antenna fitted with a non translucent cover.Then again I really dont understand why you want to keep the light away from the antenna!!!!

Brian Goldsmith.

Way back yonder when Flintstone was just a slip of a lad, the TV aerials had to be high. LightNing hit next doors' aerial and ran down the disconnected

300 ohm ribbon to blow a rather large hole in the concrete floor. I've been a bit sus of bright flashes and loud bangs ever since .

For coax, a 90V GDT (gas discharge tube) between the inner and outer conductors and earthing the cable screen is about all you can do.

It's a bit tricky to substantially earth the screen on RG59 though.

One of these might be the go:

I used Polyphaser (I think) protection devices on an array of HF antenna near Darwin and on Bathurst Island a few years ago. Very expensive though. Lightning strikes happen quite often in the tropics, so its only a good idea to incorporate them in your system if that's your location AND you are prepared to put up with the expense. BUT you (preferably an expert) would have to design the system to accomodate the very high currents that would occur in the event of a direct lightning strike. A very large solid copper strap (say 75mm wide by 3mm thick) and short, would have to connect the shield connection of the protection device to a very good ground, say a 2 metre solid copper rod belted into the ground at the coax entry point, where the protection device is located. No braids. Most people would simply increase their insurance and put up with the inconvenience of a dead tv, and having to replace the antenna and coax occasionally. If you're not in high lightning strike zone, you might as well chance it, like the rest of us.

Thanks for the answers - I kind of suspected that remotely effective lightning (see, I can spell, somtimes) protection was a big ask for an antenna, but after a TV got fried by a strike, I thought I should check...

On 6 Apr 2005 19:38:30 -0700, "David L. Jones" put finger to keyboard and composed:

A friend's house has been hit twice. He lost most of his electronic equipment on the last occasion. His neighbour was worse off - his meter box had to be replaced. Fortunately my friend was insured.

- Franc Zabkar

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Please remove one 's' from my address when replying by email.

That's from the lightening hitting his power supply not the aerial. Most lightening hits come from the power supply, being hit on your aerial is very unlikely.

"Bodgey" wrote

That's from the lightening hitting his power supply not the aerial. Most lightening hits come from the power supply, being hit on your aerial is very unlikely.

***** The mind boggles!!!!!!!!!

Brian Goldsmith.

Really? Why did I find pieces of my TV antenna more than 150 feet from the mast after it exploded from a lightning strike? The same strike burnt open the underground phone line for more than a mile out to the highway where it destroyed the electronics in the phone companies pedestal? it also damaged a computer and monitor that had no cables connected when lightning hit the antenna. Over $2000 dollars worth of damage including battery powered items that had IC chips explode from the EMP.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

On Sat, 09 Apr 2005 21:33:02 GMT, "Bodgey" put finger to keyboard and composed:

I agree. I was just making the observation that some people have a good reason to be paranoid. In fact another friend's house (at a different location) has also been hit more than once. His strikes came via the power supply, too.

- Franc Zabkar

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Please remove one 's' from my address when replying by email.

That is actually about as incorrect as you can get. In fact most Lightning damage comes from sources other than Lightning strikes to MEN mains. ie: Phone Lines (yes even underground ones) Aerials and direct strikes to houses

Mornin, Mains sure can bring in a lot of overvoltages - happens all the time. True, the neutral is bonded to earth in many places (ie earth bar in MSB, to every power pole, to high voltage earth etc). This isn't saying stikes dont occur elsewhere but they often come in via the mains. Its not only lighting either, tree branches can often force the HV lines down onto the LV lines, sending 50Hz high voltage into houses. While the lines will trip out on earth fault quickly it will still cause damage to appliances.

Getting back to the OT, earthing the pole will help, but in the event of a direct strike you'll still most likley do damage to your TV. What it may do tho is prevent the many kA's coming inside and damaging lots of other things too. Unplugging is best - I usually do that when things aren't in use or a storm is approaching - lots of lightning around here

Cheers James

That is obviously the Lightning entering the MEN mains, avoiding all those unpopular Earth stakes and exiting out via the Antenna...... After all the Antenna is Metal remember ! (semi-quote from one of the more Technically stupid movies I have ever had the Misfortune to watch - Hard rain )

The same

But where is w_tom ? he reckons that Telco equipment is never damaged by Lightning Strikes ....

it also damaged a computer and monitor that had no cables

Just wait w_tom will be along shortly to tell you what really happened ;-)

On Wed, 13 Apr 2005 16:28:03 +1000, "Richard Freeman" put finger to keyboard and composed:

Hmmm, that seems counterintuitive. I would have thought that a strike on the mains would affect several households and would take out expensive appliances. OTOH, a strike on the phone line may take out your phone or your modem, but not much else. Strikes on aerials would also be localised events.

- Franc Zabkar

--
Please remove one 's' from my address when replying by email.

Not at all. While that does happen, when lightning enters phone lines, look out. I saw two very dead and burnt motherboards that were connected via modem to the phone lines. One was actually warped and twisted from the heat. The strike was half a k up the road and just like Richard mentioned, entered the phone lines through the ground. I don't know why mains strikes seem to have a smaller radius of damage (maybe all the neutral grounding? maybe the higher load presented by all the connected appliances? higher capacitance? probably all of above), but it has always been said to disconnect your modems during electrical storms.

Of course the reality is that a strike is going to cause damage to whatever it hits. It's just where it goes and via what medium after that.

Bryan

It is largely a Conclusion I drew having Visited/Repaired many Data communications and Computer installations following Lightning Strikes. my observations where as follows:

Most damage to Computer systems was pretty well confined to equipment that was connected to Data lines, Aerials and or internal building cabling (other than AC mains) with equipment plugged into AC mains alone more often than not surviving unscathed. Arc tracks from Lightning consistently showed signs of arcing from unearthed phone lines, aerials etc (line interfaces etc) typically across to chassis and earthed equipment metalwork but I do not recall ever seeing evidence of arcing from AC mains connections to Earthed metalwork.

And every other Phone/modem/LI etc connected to that cable and often the cable itself - Conterary to popular belief underground cables are just as susceptible to Lightning damage (some people I have spoken to have argued that they are in fact more susceptible) as aerial cables due to effects such as EPR,EMP etc In fact I have seen Lightning strikes that have blown over

200 surge arrestors off the MDF terminating an underground cable and still destroyed equipment in the building and this from strikes to the cable over 100m from the building. In fact one strike I cleaned up after at the most inappropriately named Mount Peasant (google groups search for 'mt pleasant' in aus.electronics for the tale - and other tales of my Lightning experiences) blew the tripe out of 50 surge arrestors, damaged faxes, modems and Eftpos machines etc and still damaged a connector at the other end of over 5kms of cable.

That is correct In fact most Lightning damage I have seen is localised in nature with the exception of Lightning strikes to phone cables.

It seems counter intuitive until you realise that MEN power Distribution as the name suggests employs a Multiple earthed Neutral (a single earth stake is in fact inadequate during a Lightning strike as a Lightning strike usually causes an EPR often exceeding 100,000 Volts) is made up of relatively low impedance cabling and often also employs lighting protection such as earthed wires above the power lines etc.....

Regards Richard Freeman