In article , Chris Hogg scribeth thus
Not quite so..
It copes .. just that these days with Mr Pikey and his ilk liking that lovvery coloured metal more likely than not Ally is the one of choice nowadays.
Quite a few comms sites now have labels advising the outlaws that;
.. "All Copper has been removed from this site"!...
In article , Harry Bloomfield scribeth thus
Must have been some very thin copper then. Was it done properly in the first place?.
Was it even earthed correctly, that hadn't come undone at all?...
klystrons and magnetrons are 'valves' of a sort..
Oy, will you lot stop doing that? There is no "e" in lightning.
tony sayer formulated on Tuesday :
No it was as near as I could tell the proper stuff. Had it not been properly earthed, the resistance to ground would have been higher, so less current might/would have flowed. What I can say, it was one hell of a bang, but never having witnessed such a close strike it was difficult to compare.
You are correct, it also explains why it forks - it 'sees' a similarly useful path to ground.
Harry Bloomfield expressed precisely :
The Internet, or rather the postings on the subjects have improved since I first tried to research the covering of mirrors and opening of windows during a storm. There are now lots of mentions on the subjects. It wasn't just my mother then lol
All this talk about lightning and not a peep from that Tom bloke,
guess he must have bolted or been discharged from this world.
G.Harman
My sig has been as below for a long time - hopefully it threw up lots of false positives in his searches.
Well, looking at the photo evidence, I wouldn't doubt your friend's flat had been hit by a lightning strike on the TV antenna. It might not have been the return stroke, possibly just the leader (otherwise your friend may well have had to bring in building contractors to repair the damage more typical of a direct strike).
As for your question regarding the voltage, you can certainly count on it being in the ballpark of a few tens of Kilovolts where the attenuated energy of the strike materialised around the entertainment interconnects.
You could expect hundreds of amps out of a typical lighting bolt's core channel of 25 to 100KA (alongside of the several KV leftover from the hundreds of MVs of the cloud to ground or ground to cloud return stroke).
When the evidence shows such gross electrical damage as those pictures do, only be surprised _if_ any of the attached kit shows any functionality at all.
Lightning strikes create transient conditions so unlike what we're used to with our tamed "230" V ac mains supplies, that we may sometimes see the most improbable of survivals of electronic kit whereby, for example, the antenna socket was blown to smithereens yet a temporary connection revealed an otherwise fully functional tuner(/amp) merely in need of a replacement antenna socket.
It's rare to find such 'survivors' amongst the 'wreckage' / 'carnage' / 'mayhem' as experienced by yor friend but not totally unknown. Since you seem to have described a full complement of 'blown' kit, it appears, unsurprisingly, that none of the kit survived the event.
That is unlucky. Even when it has vapourised the resulting plasma should still be mostly the path of lowest resistance. But fast high voltage electricity can be fickle about the route it takes.
I have seen ones that had clearly been red hot or more from the fresh oxide colour that the previously carbonate green copper had acquired.
These guys are fun if you ever get the chance to see them - UK's own version of Arc Attack called Lords of Lightning at approx 2MV each.
(do NOT try this at home folks!)
Regards, Martin Brown
In article , Harry Bloomfield scribeth thus
Well the normal stuff is around and inch by eighth and thats stands up to it. Older buildings used somewhat thinner but one up on Ely cathedral is around 3/4 inch and not too thick and thats been there since .. well Ben Franklin was a lad I reckon;!. Did anyone see any samples of it at all for analysis afterwards?..
TWTs you may find in orbit, delivering satellite TV, but for DTT methinks you're thinking of IOTs (inductive output tubes) aka 'Klystrodes' - a sort of cross between a klystron and a tetrode.
I just !Want! a Tesla coil for Xmas:))....
Yep!, certainly was. Interesting that the Klystode was discussed in the book the Pye TVT story some time ago!.
And that book you could describe it as the history of broadcast TV in the UK and a bit further afield;).. ..
You have to keep in mind that lightning strikes involve tens of thousands of amps with rise times measured in microseconds from a voltage source of several millions of volts (a high resistance earth connection or even a missing 20 foot section will have hardly any effect on such a "Constant Current Source).
This sort of free electricity seems to follow a completely different set of rules, even compared to the 400KV used in overhead power lines.
If you take the trouble to examine the lightning conductors on a building (say a church steeple) using binoculars, you should note that the lightning conductor very gently curves past any ledges and other such protrusions in a properly installed lightning protection system.
A lightning conductor is a conductor only in the sense that it acts like "A suggested path" with about as much authority as a "Serving suggestion" on the packaging of a 'readymeal'.
If the lightning conductor were to follow the contour of a ledge too closely, the lightning bolt simply bypasses the high inductance of the 'diversion', blowing the intervening stonework to bits.
Most of the current takes the form of a plasma formed on the surface of the conductive strip of copper (skin effect from the extremely high delta Amps/microsecond rise time means the volt drop of the surface current causes the air to ionise and become a highly conductive plasma).
The only time a lightning conductor behaves like a conventional conductor is when the pointy bits at the top are drawing away static charge build up via the corona discharge mechanism (probably just prior to the inevtable strike).
t by lightning via their roof aerial.
The TV which was under guarentee, they reported the non-functioning TV to c urrys/pcworld who arranged for a samsung engineer to come last saturday. He could tell what had happend, and replaced two boards and the TV worked a gain, no charge for this repair was asked for.
Virgin media came within a day or two and replaced both the super hub and t he cable box for free. Well theyshould do I guess as we pay rental for them , but I've heard anothers in the area with similar problems with BT haven't been so 'lucky' and have been charged although I have no details.
My Nan used to do that - all mirrors covered as soon as there was any suggestion of a storm.
I remember asking why and she pointed out that her house had never been struck by lightning so it must work...
Darren
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