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Default Lightning strike


Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got hit by lightning via their roof aerial.
The arail itself doesn't appear to be damaged.

It appears that the lightning went down the aerial cable to the aerial plug which was connected to the inline attenuator, the centre pin of the aerail plug was found about 5ft away it must have been very hot as it embedded itself info the carpet leaving a black burn mark around it.
The aerial plug/attenuator had been connected to the DVD recorder which no longer functions. The aerial plug/attenuator/lead had been separated in the 'blast' even the aerial plug had been separated from it's lead. I think the surge then went either through the SCART lead which didm't appear damaged to the 42" LED TV which no longer works although there's no sign of physical damage. The surge seems to also have gone down a HDMI lead from the TV to the TV cable box, destroying that although the only physical sign is where I pulled out the HDMI lead. it also appears to have travelled through a 2nd HDMI to an adapter to a G5 iMac as the TV was connected as a 2nd monitor. The G5 iMac no longer works although it sounds as if the HD spins up. The virgin media super hub 2 was also knocked out as this was connected to the TV via an ethernet cable. A set of speakers were also found to be not working.

It also appears that a cable distribution box out in the street was also hit as an orange glow and flash was seen at the time.

https://www.flickr.com/photos/whisky...7645996828015/

Photo 1 Damaged to the ~5mm diameter aerial lead
Photo 2 Aerial plug and attenuator
Photo 3 Aerial plug and attenuator & centre pin
Photos 4&5 Fuse had vapourised just leaving the metal end caps, and it also blew off the plug top.
Photo 6 The HDMI lead from the TV to the cable TV box, this end was connected to the cable TV box, it took a bit of pulling to get it out and the internal pins of the cable TV box came out with it.
The cable TV box was no longer working.
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The day after we had that amazing lightning in London - the like of which
I've never seen here before - the audio amp in my workshop was dead. Both
channels. Power supply was just fine - both input chips which do the
balanced to unbalanced had failed. The schematic I drew of it when
designing/building it was dated 1997, and it's worked fine every day - and
for much of each day ever since.

Everything else in the house seems ok - but of course I might come across
something little used at a later date.

Could just be coincidence, I suppose. Simply replaced them and it's been
fine since.

--
*It was recently discovered that research causes cancer in rats*

Dave Plowman London SW
To e-mail, change noise into sound.
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Well really, almost everything in a house is usually trashed. I do know for
example that down my street the company I worked for was struck while i was
coming out for my lunch break.
It had lightening condutors all around it, but none of the computers ever
worked again, it even trashed the coffee machine in the lobby.

As you say, some things look like they have been damaged, but most just stop
working and often so much of their innards are trashed, its not worth fixing
them, cost wise.
sorry to say, but Lightening is one of the most destructive natural
elements that can in the shortest time ruin our tech. It does not do humans
much good either.
I used to work back in the old days of the 60s, at a now non existent tv
rental repair place in sw London, and when stuff used to arrive back from
places like the Welsh hills with lightening damage written on them, it was a
bin job. Holes in pcbs, Charred capacitors and melted plastic bits and
pieces. In one case where the cable input transformer was was just a chared
hole.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"whisky-dave" wrote in message
...

Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got hit
by lightning via their roof aerial.
The arail itself doesn't appear to be damaged.

It appears that the lightning went down the aerial cable to the aerial plug
which was connected to the inline attenuator, the centre pin of the aerail
plug was found about 5ft away it must have been very hot as it embedded
itself info the carpet leaving a black burn mark around it.
The aerial plug/attenuator had been connected to the DVD recorder which no
longer functions. The aerial plug/attenuator/lead had been separated in the
'blast' even the aerial plug had been separated from it's lead. I think the
surge then went either through the SCART lead which didm't appear damaged
to the 42" LED TV which no longer works although there's no sign of physical
damage. The surge seems to also have gone down a HDMI lead from the TV to
the TV cable box, destroying that although the only physical sign is where I
pulled out the HDMI lead. it also appears to have travelled through a 2nd
HDMI to an adapter to a G5 iMac as the TV was connected as a 2nd monitor.
The G5 iMac no longer works although it sounds as if the HD spins up. The
virgin media super hub 2 was also knocked out as this was connected to the
TV via an ethernet cable. A set of speakers were also found to be not
working.

It also appears that a cable distribution box out in the street was also hit
as an orange glow and flash was seen at the time.

https://www.flickr.com/photos/whisky...7645996828015/

Photo 1 Damaged to the ~5mm diameter aerial lead
Photo 2 Aerial plug and attenuator
Photo 3 Aerial plug and attenuator & centre pin
Photos 4&5 Fuse had vapourised just leaving the metal end caps, and it also
blew off the plug top.
Photo 6 The HDMI lead from the TV to the cable TV box, this end was
connected to the cable TV box, it took a bit of pulling to get it out and
the internal pins of the cable TV box came out with it.
The cable TV box was no longer working.


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whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct
on.Almost a couple of decades ago our local church tower (stone built)
100 yards away was struck, it did considerable damage inside the church
tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed. It also took many phone lines out in the
village.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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From the Sofa of Brian Gaff Reply address is active
"whisky-dave" wrote in message
...

Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got
hit by lightning via their roof aerial.
[....]

On 28/07/14 18:30, Brian Gaff wrote:
Well really, almost everything in a house is usually trashed. I do know for
example that down my street the company I worked for was struck while i was
coming out for my lunch break.
It had lightening condutors all around it, but none of the computers ever
worked again, it even trashed the coffee machine in the lobby.

As you say, some things look like they have been damaged, but most just stop
working and often so much of their innards are trashed, its not worth fixing
them, cost wise.
sorry to say, but Lightening is one of the most destructive natural
elements that can in the shortest time ruin our tech. It does not do humans
much good either.
I used to work back in the old days of the 60s, at a now non existent tv
rental repair place in sw London, and when stuff used to arrive back from
places like the Welsh hills with lightening damage written on them, it was a
bin job. Holes in pcbs, Charred capacitors and melted plastic bits and
pieces. In one case where the cable input transformer was was just a chared
hole.

Brian

Yep. Insurance claim on *everything* including the new house wiring they
will *insist* upon.

Take everything that don't work to a fixer of said items, get quotes and
if less than replacement get fixed, otherwise replace.

Months of hassle ahead/.

Good luck


--
Everything you read in newspapers is absolutely true, except for the
rare story of which you happen to have first-hand knowledge. Erwin Knoll


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On Mon, 28 Jul 2014 08:37:56 -0700 (PDT), whisky-dave wrote:

On Friday 25th July 2014 about midday in E17 London a friends flat got
hit by lightning via their roof aerial. The arail itself doesn't appear
to be damaged.


Personally I don't think they got a direct hit, maybe a streamer with
the main stoke(s) hitting close by.

As others have said a direct hit does tremendous damage not just to
electronics but the structure and fixed wiring. It's not unknown for
all the fixed wiring to be instantally vapourised and blow itself out
of the walls.

Your description of minimal damamge to some zapped, interconnected,
electronics is more a kin to the affects of a near by strike. "near
by" meaning up to a few hundred yards.

Get 'em to go through every single bit of kit in the place and make
sure it a) works b) shows no sign of damage. Anything that fails bung
in an insurace claim for.

--
Cheers
Dave.



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On 28/07/2014 19:02, Harry Bloomfield wrote:
whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct on.Almost
a couple of decades ago our local church tower (stone built) 100 yards
away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed. It also took many phone lines out in the
village.

So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?
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Dave Liquorice wrote:

Get 'em to go through every single bit of kit in the place and make
sure it a) works b) shows no sign of damage. Anything that fails bung
in an insurace claim for.


Items damaged by lightning then repaired often fail again before long.

Bill
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In article , Brian Gaff
scribeth thus
Well really, almost everything in a house is usually trashed. I do know for
example that down my street the company I worked for was struck while i was
coming out for my lunch break.
It had lightening condutors all around it, but none of the computers ever
worked again, it even trashed the coffee machine in the lobby.

As you say, some things look like they have been damaged, but most just stop
working and often so much of their innards are trashed, its not worth fixing
them, cost wise.
sorry to say, but Lightening is one of the most destructive natural
elements that can in the shortest time ruin our tech. It does not do humans
much good either.


Nope. Sure doesn't. It does need handling with care and if its done
right then it can be contained to where it needs to go and thats passing
by all your expensive kit.

Radio and TV stations and Cellphone masts are designed to cope with it
they simply have to as such high structures are more likely than not
liable to be walloped and they can't be out of commission for that
reason.

Good levels of protection aren't cheap and in an "uncontrolled"
discharge the currents will just go where they find least resistance
path and usually many more than the one of them.


I used to work back in the old days of the 60s, at a now non existent tv
rental repair place in sw London, and when stuff used to arrive back from
places like the Welsh hills with lightening damage written on them, it was a
bin job. Holes in pcbs, Charred capacitors and melted plastic bits and
pieces. In one case where the cable input transformer was was just a chared
hole.

Brian


Usually .. except that someone I know had the TV aerial walloped not
directly, that was the house a few doors away, took out their FM tuner
and they gave me the Audiolab amp which just had a blown fuse and a bit
if charred track, mended that and been fine ever since...

The current had come down the Tuner phono lead looking for an earth and
found one across the input PCB tracks to the earth wire and that was
that.


--
Tony Sayer


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In article , ss
scribeth thus
On 28/07/2014 19:02, Harry Bloomfield wrote:
whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct on.Almost
a couple of decades ago our local church tower (stone built) 100 yards
away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed.


Blimey!, what do you wear at night metal pants;?..

It also took many phone lines out in the
village.

So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?



Unplug it, it may not make a lot off difference in a direct strike but
for a nearby sideswipe it can make the odds more in your favour.

My Gran used to put the aerial lead to her valve "wireless" in a large
glass jar to keep natures leccy in;!...

--
Tony Sayer




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On 28/07/2014 20:33, ss wrote:
On 28/07/2014 19:02, Harry Bloomfield wrote:
whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct on.Almost
a couple of decades ago our local church tower (stone built) 100 yards
away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed. It also took many phone lines out in the
village.

So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


Unplug, leaving a sizeable gap between plug and socket. Not forgetting
the connection to your cable connection, even if it *does* run
underground. Switching off just leaves a nice spark gap inside the switch.

Or, if you're in a town, do the same as everybody else and take your
chances that it'll be the next street but one that gets zapped.

--
Tciao for Now!

John.
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On 28/07/2014 16:37, whisky-dave wrote:

Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got hit by lightning via their roof aerial.
The arail itself doesn't appear to be damaged.

It appears that the lightning went down the aerial cable to the aerial plug which was
connected to the inline attenuator, the centre pin of the aerail plug

was found about 5ft away
it must have been very hot as it embedded itself info the carpet

leaving a black burn mark around it.
The aerial plug/attenuator had been connected to the DVD recorder which no longer functions.
The aerial plug/attenuator/lead had been separated in the 'blast'

even the aerial plug had
been separated from it's lead. I think the surge then went either

through the SCART lead
which didm't appear damaged to the 42" LED TV which no longer works

although there's no sign of physical damage.

The surge seems to also have gone down a HDMI lead from the TV to the

TV cable box, destroying
that although the only physical sign is where I pulled out the HDMI

lead. it also appears to
have travelled through a 2nd HDMI to an adapter to a G5 iMac as the

TV was connected as a 2nd monitor.


The G5 iMac no longer works although it sounds as if the HD spins up. The virgin media super hub 2 was
also knocked out as this was connected to the TV via an ethernet

cable. A set of speakers were also found to be not working.

Worth checking fuses you might be lucky with some of them.

It also appears that a cable distribution box out in the street was also hit as an orange glow and flash was seen at the time.


That could be damage due to induced current flowing in the local loop.

https://www.flickr.com/photos/whisky...7645996828015/

Photo 1 Damaged to the ~5mm diameter aerial lead
Photo 2 Aerial plug and attenuator
Photo 3 Aerial plug and attenuator & centre pin
Photos 4&5 Fuse had vapourised just leaving the metal end caps, and it also blew off the plug top.
Photo 6 The HDMI lead from the TV to the cable TV box, this end was connected to the cable TV box,
it took a bit of pulling to get it out and the internal pins of the

cable TV box came out with it.
The cable TV box was no longer working.


I'd hazard a guess at around 1000A pulse current with the voltage not
well defined. I have been in a building that took a direct hit once and
it vaporised most of the phone lines blowing the trunking off the wall.
It took about a week to be repaired and the switchboard operator was
inconsolable and quite alarmingly deaf for a day or so. It did curious
damage to the local mainframe too. The transient protectors protected
themselves by allowing more expensive components to fry first

The annoying thing was that there were supergrid pylons taller than our
building nearby that didn't get hit at all. It was found afterwards that
some scrotes had pinched the bottom 20' of our lightning conductor.

On another occasion at about this time of year I narrowly missed seeing
a display of ball lightning witnessed by other physicists.

You really don't want to be too close to these events. Tree trunks can
explode from internal steam pressure generated in a direct hit.

Regards,
Martin Brown
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On Mon, 28 Jul 2014 20:54:19 +0100, tony sayer wrote:

The resulting pulse, at around 2 in the morning, blew my large

sat
system, a video and several other items. It either the pulse or

the
noise, lifted me off the bed.


Blimey!, what do you wear at night metal pants;?..


I'd go for the noise and a hefty whack "fight or flee"...

So should we disconnect stuff if there is a nearby electrical

storm?

I switch off the ADSL modem but that's nothing to do with trying to
stop it being zapped. It's to stop the electrical noise inducing
resysncs and pushing the speed down. It'll recover automagically but
may take a day or two.

If the answer is yes, is that unplug as opposed to just switch

off?

Unplug it, it may not make a lot off difference in a direct strike but
for a nearby sideswipe it can make the odds more in your favour.


Maybe but if there are other cables besides the power they'll get
hefty induced currents and voltages in 'em, enough to zap
input/output stages.
TBH disconecting everything is too much faff, have tested and
configured spares for key bits, like ADSL modem, network switch and
insurance. If lighting strikes there is not a lot you can do without
spending serious amounts of money.

--
Cheers
Dave.



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tony sayer laid this down on his screen :

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed.


Blimey!, what do you wear at night metal pants;?..


I've no idea what caused it, but I woke up landing back on the bed,
whilst hearing the massive thump.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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After serious thinking tony sayer wrote :
My Gran used to put the aerial lead to her valve "wireless" in a large
glass jar to keep natures leccy in;!...


My mother used to cover all of the mirrors over ????

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


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ss has brought this to us :
So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


The chances of a direct strike for most people is very remote, but it
depends on your location and whether there are other close higher
buildings.

Tall buildings will attract the main strike, but will increase your
chances of suffering the pulse damage.

Generally you have much more chance of a near local strike causing
damage simply due to the EM pulse, than a direct strike. Any cable or
wire which travels any distance can pick up the pulse, which can then
make its way into sensitive modern circuits and blow them. So
disconnect any antennas, phone cables and unplug items from the mains.

Having said that, I have an absolute mass of electronics here and lots
of antennas, but despite having suffered quite a lot of damage in the
incident I mentioned earlier, I soon became fed up of unplugging things
and now no longer bother.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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"ss" wrote in message
...
On 28/07/2014 19:02, Harry Bloomfield wrote:
whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct on.Almost
a couple of decades ago our local church tower (stone built) 100 yards
away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed. It also took many phone lines out in the
village.


So should we disconnect stuff if there is a nearby electrical storm?


Yes, if you want to reduce the risk of stuff getting damaged.

Lot of work tho.

I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


You need to unplug it, not just switch it off.

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Harry Bloomfield wrote:
After serious thinking tony sayer wrote :
My Gran used to put the aerial lead to her valve "wireless" in a large
glass jar to keep natures leccy in;!...


My mother used to cover all of the mirrors over ????


When I was a student in digs, my landlady would rush to replace any
failed light bulb, otherwise it would "fill the house with electricity".

I assume she grew up with gas lighting and didn't quite grasp the
difference between a bulb and a flame.

--
Mike Barnes
Cheshire, England
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On Mon, 28 Jul 2014 21:04:48 +0100, Martin Brown
wrote:

On another occasion at about this time of year I narrowly missed seeing
a display of ball lightning witnessed by other physicists.

Regards,
Martin Brown


Arriving at my house in the middle of a storm I witnessed ball
lightning rolling quite slowly across the roof tops; a truly eerie
sight. Luckily I had all my amateur radio kit disconnected except for
the rotator control box. Every component was physically destroyed and
all of the copper PCB track was vaporized onto the inside of the
casing. The only other damage was a power diode in the TV and pre-amp
IC in the Hi-Fi. We got off lightly compared to some neighbours.

Mike
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PS, the only item I had trashed by lightening was a fax machine which went
on churning out blackened paper till I pulled the plug. It was repaired
under warranty as apparently the surge protection had been left out of a
batch which included mine!
I was on BT then and it was assumed the induced current in the line which
ran overgound was to blame.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Brian Gaff" wrote in message
...
Well really, almost everything in a house is usually trashed. I do know
for example that down my street the company I worked for was struck while
i was coming out for my lunch break.
It had lightening condutors all around it, but none of the computers ever
worked again, it even trashed the coffee machine in the lobby.

As you say, some things look like they have been damaged, but most just
stop working and often so much of their innards are trashed, its not worth
fixing them, cost wise.
sorry to say, but Lightening is one of the most destructive natural
elements that can in the shortest time ruin our tech. It does not do
humans much good either.
I used to work back in the old days of the 60s, at a now non existent tv
rental repair place in sw London, and when stuff used to arrive back from
places like the Welsh hills with lightening damage written on them, it was
a bin job. Holes in pcbs, Charred capacitors and melted plastic bits and
pieces. In one case where the cable input transformer was was just a
chared hole.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"whisky-dave" wrote in message
...

Anyone have any idea what sort of voltage etc. this might have been.

On Friday 25th July 2014 about midday in E17 London a friends flat got hit
by lightning via their roof aerial.
The arail itself doesn't appear to be damaged.

It appears that the lightning went down the aerial cable to the aerial
plug which was connected to the inline attenuator, the centre pin of the
aerail plug was found about 5ft away it must have been very hot as it
embedded itself info the carpet leaving a black burn mark around it.
The aerial plug/attenuator had been connected to the DVD recorder which no
longer functions. The aerial plug/attenuator/lead had been separated in
the 'blast' even the aerial plug had been separated from it's lead. I
think the surge then went either through the SCART lead which didm't
appear damaged to the 42" LED TV which no longer works although there's no
sign of physical damage. The surge seems to also have gone down a HDMI
lead from the TV to the TV cable box, destroying that although the only
physical sign is where I pulled out the HDMI lead. it also appears to have
travelled through a 2nd HDMI to an adapter to a G5 iMac as the TV was
connected as a 2nd monitor. The G5 iMac no longer works although it sounds
as if the HD spins up. The virgin media super hub 2 was also knocked out
as this was connected to the TV via an ethernet cable. A set of speakers
were also found to be not working.

It also appears that a cable distribution box out in the street was also
hit as an orange glow and flash was seen at the time.

https://www.flickr.com/photos/whisky...7645996828015/

Photo 1 Damaged to the ~5mm diameter aerial lead
Photo 2 Aerial plug and attenuator
Photo 3 Aerial plug and attenuator & centre pin
Photos 4&5 Fuse had vapourised just leaving the metal end caps, and it
also blew off the plug top.
Photo 6 The HDMI lead from the TV to the cable TV box, this end was
connected to the cable TV box, it took a bit of pulling to get it out and
the internal pins of the cable TV box came out with it.
The cable TV box was no longer working.






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In article ,
ss wrote:
On 28/07/2014 19:02, Harry Bloomfield wrote:
whisky-dave formulated on Monday :
Anyone have any idea what sort of voltage etc. this might have been.


That looks more like the result of a near strike than a direct on.Almost
a couple of decades ago our local church tower (stone built) 100 yards
away was struck, it did considerable damage inside the church tower.

The resulting pulse, at around 2 in the morning, blew my large sat
system, a video and several other items. It either the pulse or the
noise, lifted me off the bed. It also took many phone lines out in the
village.

So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


If you unplug during the storm, the lighting strike might come ast the
moment you have the plug in you hand, Not good.

--
From KT24

Using a RISC OS computer running v5.18

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On Tue, 29 Jul 2014 08:09:38 +0100, charles
wrote:


So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


If you unplug during the storm, the lighting strike might come ast the
moment you have the plug in you hand, Not good.


Mother had a close call back in the 60's.
The house was almost the highest point on a hill and Lightning often
struck nearby, being on overhead lines the power often went so an oil
lamp was made ready and placed on the dining table which was close to
the window. Unplugging the aerial for the TV was std procedure but
Mother got it wrong one day and unplugged it from the socket and not
the less accessible back of the TV, the socket like many back in
early VHF days was mounted on the wooden window frame. It was about
15 mins later that arc leapt from the socket and hit the metal base of
the Aladdin oil lamp about 3 ft away which as Mother was sat at the
table made her jump a bit the lamp at least intercepting the arc
before it reached her.
Could not have been a direct hit but the old extra large VHF aerial
dad installed to get ITV before the area was officially covered
gathered a charge on more than one occasion,Mother never really
understood unplugging the aerial as on another occasion she unplugged
from the back of the set but being a tidy type rather than leave the
end on the floor coiled it up and placed it on the wide internal sill.
A while later Dad placed a cup of Coffee on the sill while doing some
p/work at the table not really noticing the aerial lead which having
been slightly knocked unwound itself from behind the curtain where
mother had hid it coming to rest in the saucer wet from some spilt
tea. Dad got stimulated by the coffee in a way never before when he
picked the cup up grounded the lead and saucer most of the coffee
being flung around the room. It was painful for him but quite funny to
watch.

G.Harman
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On 29/07/2014 09:13, wrote:
On Tue, 29 Jul 2014 08:09:38 +0100, charles
wrote:


So should we disconnect stuff if there is a nearby electrical storm?
I am on cable so no dishes or aerials.
If the answer is yes, is that unplug as opposed to just switch off?


External aerials are the biggest risk factor. You could be unlucky with
cable, but the strike will likely find an easier path to ground first.

If you unplug during the storm, the lighting strike might come ast the
moment you have the plug in you hand, Not good.


Could not have been a direct hit but the old extra large VHF aerial
dad installed to get ITV before the area was officially covered
gathered a charge on more than one occasion,Mother never really
understood unplugging the aerial as on another occasion she unplugged
from the back of the set but being a tidy type rather than leave the
end on the floor coiled it up and placed it on the wide internal sill.
A while later Dad placed a cup of Coffee on the sill while doing some
p/work at the table not really noticing the aerial lead which having
been slightly knocked unwound itself from behind the curtain where
mother had hid it coming to rest in the saucer wet from some spilt
tea. Dad got stimulated by the coffee in a way never before when he
picked the cup up grounded the lead and saucer most of the coffee
being flung around the room. It was painful for him but quite funny to
watch.


It is worth remembering that a TV aerial on top of a house can have a
noticeable potential difference to ground on its aerial lead. Enough to
easily light an neon screwdriver and on active days I have had the odd
minor belt off one from the nominally outer case earthy side!

Only really a problem when installing aerials and tweaking satellite
dishes when there is some unsuspected electrical storm activity about.

Regards,
Martin Brown

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On Tue, 29 Jul 2014 08:25:33 +0000 (UTC), Jethro_uk wrote:

It still puzzles me how a lightening bolt chose a tree halfway up a hill
with a sodding pointy church on the top with the mother of all
lightening rods.


Lightening rods/protection work by enabling the building up charge to
leak into the atmosphere from the nice pointy tips. The idea being
that the voltage doesn't rise high enough to flash over. The charge
is dissipated over minutes rather than ms. A dry, relatively round
and high resistance, tree doesn't leak the charge so the voltage can
build up to the atmospheric breakdown point.

--
Cheers
Dave.



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On Monday, 28 July 2014 22:26:45 UTC+1, Harry Bloomfield wrote:
After serious thinking tony sayer wrote :

My Gran used to put the aerial lead to her valve "wireless" in a large


glass jar to keep natures leccy in;!...




My mother used to cover all of the mirrors over ????


Were you really that ugly as a kid ;-)

sorry couldn't resist the obvious.




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Jethro_uk brought next idea :
There was an apocalyptic cover to "Electronics Today International" (I
used to subscribe !) in the 80s, with a mushroom cloud, and a special
article detailing the damage the EMP from a nuclear blast could do ...
transistorised equipment - particularly MOSFET - was very vulnerable.
While valve equipment was effectively immune.


I remember the article well. The Russkies continued to use and develop
valves long after we abandoned them, likely for their tolerance of EMP.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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Jethro_uk explained on 29/07/2014 :
It still puzzles me how a lightening bolt chose a tree halfway up a hill
with a sodding pointy church on the top with the mother of all lightening
rods.


It chooses both the best and most direct route to discharge itself.
Obviously, that was the tree.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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It happens that Chris Hogg formulated :
I do
wonder whether the copper strip often used could actually cope with
the currents involved anyway, or would it just vaporise.


They do on occasion vaporise. The church close to us which was struck,
which I mentioned earlier, had a lightning conductor. The copper had
vaporised and the discharge then made its way via the stone work of the
steeple, through the wall and had then tracked its way down inside, via
the plaster.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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On 7/29/2014 11:56 AM, Harry Bloomfield wrote:
It happens that Chris Hogg formulated :
I do
wonder whether the copper strip often used could actually cope with
the currents involved anyway, or would it just vaporise.


They do on occasion vaporise. The church close to us which was struck,
which I mentioned earlier, had a lightning conductor. The copper had
vaporised and the discharge then made its way via the stone work of the
steeple, through the wall and had then tracked its way down inside, via
the plaster.

My father had a 23ft radio mast on the roof. The house was halfway down
a hill, and even with the mast, there were taller things
nearby...lightning struck the mast, travelled down three storeys, and
vaporised the glass fuse in his two-way radio.
There was no melted glass visible - the fuse simply disappeared.
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whisky-dave presented the following explanation :
On Monday, 28 July 2014 22:26:45 UTC+1, Harry Bloomfield wrote:
After serious thinking tony sayer wrote :

My Gran used to put the aerial lead to her valve "wireless" in a large
glass jar to keep natures leccy in;!...




My mother used to cover all of the mirrors over ????


Were you really that ugly as a kid ;-)

sorry couldn't resist the obvious.


No she covered up the mirrors, not me :-?

Another thing she did, was open windows too. The explanation I was
given, was to let out the ball lightning should it come down the
chimney. I seem to remember the explanation for covering the mirrors,
was that bare mirrors attracted ball lightening, but not sure on that
point.

Bless, she was very superstitious, but I have not come across similar
before or since.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


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On Tue, 29 Jul 2014 16:51:28 +0100, Harry Bloomfield wrote:

It still puzzles me how a lightening bolt chose a tree halfway up

a
hill with a sodding pointy church on the top with the mother of

all
lightening rods.


It chooses both the best and most direct route to discharge itself.


No, it takes the path of least "resistance", that may or may not be
the most direct route. Think about it, if lightening took the most
direct route why is it all squiggly not a straight line?

--
Cheers
Dave.



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In article , Jethro_uk
scribeth thus
On Tue, 29 Jul 2014 16:45:56 +0100, Harry Bloomfield wrote:

Jethro_uk brought next idea :
There was an apocalyptic cover to "Electronics Today International" (I
used to subscribe !) in the 80s, with a mushroom cloud, and a special
article detailing the damage the EMP from a nuclear blast could do ...
transistorised equipment - particularly MOSFET - was very vulnerable.
While valve equipment was effectively immune.


I remember the article well. The Russkies continued to use and develop
valves long after we abandoned them, likely for their tolerance of EMP.


I had a (female) friend who joined the RAF in the 80s. She had to learn
valve engineering to work on the radar systems ..


You Migh laugh but valves in the form of TWT's (travelling wave tubes)
are now in a lot of new digital TV transmitters!...

--
Tony Sayer

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In article , Jethro_uk
scribeth thus
On Mon, 28 Jul 2014 21:04:48 +0100, Martin Brown wrote:


You really don't want to be too close to these events. Tree trunks can
explode from internal steam pressure generated in a direct hit.


One night, in the 80s, I was walking, with some friends across Harrow
Hill. It was summer. Warm, not too humid, and dry. There had been no hint
of any thunderstorm.

We stopped and sat on bench about halfway up the hill, to have a
ahemcigarette/ahem. It was just after kicking out time.

Out of nowhere, a lightening strike hit a nearby (about 10m away) tree.
There was an almighty crack, and a branch *jumped* off.

A minute and a mile later, and my friends and I all agreed we had never
seen anything like it. Nor have I since.

It still puzzles me how a lightening bolt chose a tree halfway up a hill
with a sodding pointy church on the top with the mother of all lightening
rods.


Its just where the electric field was and where the resistance was less.
The old saying a Bolt from the blue has its origins in that.

I have seen a church get walloped, the catholic in Cambridge half way up
its spire around the 30 odd metre mark the spire topping out at 65..

The highest object isn't always the one that has the last path
resistance of where the field is highest...
--
Tony Sayer


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In article o.uk, Dave
Liquorice scribeth thus
On Tue, 29 Jul 2014 08:25:33 +0000 (UTC), Jethro_uk wrote:

It still puzzles me how a lightening bolt chose a tree halfway up a hill
with a sodding pointy church on the top with the mother of all
lightening rods.


Lightening rods/protection work by enabling the building up charge to
leak into the atmosphere from the nice pointy tips.


Furse who make most lightning protection in the UK now have rounded ones
than pointy ones they aren't any better so that say!..

I know which I'd prefer..



--
Tony Sayer


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In article , Chris Hogg
scribeth thus
On Tue, 29 Jul 2014 10:57:49 +0100 (BST), "Dave Liquorice"
wrote:

On Tue, 29 Jul 2014 08:25:33 +0000 (UTC), Jethro_uk wrote:

It still puzzles me how a lightening bolt chose a tree halfway up a hill
with a sodding pointy church on the top with the mother of all
lightening rods.


Lightening rods/protection work by enabling the building up charge to
leak into the atmosphere from the nice pointy tips. The idea being
that the voltage doesn't rise high enough to flash over. The charge
is dissipated over minutes rather than ms.


Pretty much my understanding also about 'lightening conductors', which
is actually a bit of a misnomer. AIUI they aren't intended to conduct
the lightening, but to prevent it happening in the first place.


Not quite so..

I do
wonder whether the copper strip often used could actually cope with
the currents involved anyway, or would it just vaporise.


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"!...
--
Tony Sayer



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In article , Harry
Bloomfield scribeth thus
It happens that Chris Hogg formulated :
I do
wonder whether the copper strip often used could actually cope with
the currents involved anyway, or would it just vaporise.


They do on occasion vaporise. The church close to us which was struck,
which I mentioned earlier, had a lightning conductor. The copper had
vaporised and the discharge then made its way via the stone work of the
steeple, through the wall and had then tracked its way down inside, via
the plaster.


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?...
--
Tony Sayer


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On 29/07/14 16:53, Jethro_uk wrote:
On Tue, 29 Jul 2014 16:45:56 +0100, Harry Bloomfield wrote:

Jethro_uk brought next idea :
There was an apocalyptic cover to "Electronics Today International" (I
used to subscribe !) in the 80s, with a mushroom cloud, and a special
article detailing the damage the EMP from a nuclear blast could do ...
transistorised equipment - particularly MOSFET - was very vulnerable.
While valve equipment was effectively immune.


I remember the article well. The Russkies continued to use and develop
valves long after we abandoned them, likely for their tolerance of EMP.


I had a (female) friend who joined the RAF in the 80s. She had to learn
valve engineering to work on the radar systems ..

klystrons and magnetrons are 'valves' of a sort..



--
Everything you read in newspapers is absolutely true, except for the
rare story of which you happen to have first-hand knowledge. Erwin Knoll
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tony sayer formulated on Tuesday :
In article , Harry
Bloomfield scribeth thus
It happens that Chris Hogg formulated :
I do
wonder whether the copper strip often used could actually cope with
the currents involved anyway, or would it just vaporise.


They do on occasion vaporise. The church close to us which was struck,
which I mentioned earlier, had a lightning conductor. The copper had
vaporised and the discharge then made its way via the stone work of the
steeple, through the wall and had then tracked its way down inside, via
the plaster.


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?...


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.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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Dave Liquorice used his keyboard to write :
On Tue, 29 Jul 2014 16:51:28 +0100, Harry Bloomfield wrote:

It still puzzles me how a lightening bolt chose a tree halfway up a
hill with a sodding pointy church on the top with the mother of all
lightening rods.


It chooses both the best and most direct route to discharge itself.


No, it takes the path of least "resistance", that may or may not be
the most direct route. Think about it, if lightening took the most
direct route why is it all squiggly not a straight line?


You are correct, it also explains why it forks - it 'sees' a similarly
useful path to ground.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
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