Discussion:
Who asked about lightening and disconnecting TV aerials?
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ARW
2021-10-12 17:06:23 UTC
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Just I have in my hand a 1964 copy of Aerial Handbook.

And it has this to say

Loading Image...

maybe we need Bill's opinion.
--
Adam
Peter Able
2021-10-12 17:48:54 UTC
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Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.

At that time, the chassis was often connected to one of the mains wires.
Too bad if you found out that the set was wrongly wired to the mains
when attempting to pull the Belling-Lee connector out of the back of the
set.

Some distribution systems leaked, too. Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.

That's for the metal-shell Belling-Lees - and for the guy who didn't
make sure that his only electrical contact was with the plug.

PA
ARW
2021-10-12 19:29:55 UTC
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Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains wires.
 Too bad if you found out that the set was wrongly wired to the mains
when attempting to pull the Belling-Lee connector out of the back of the
set.
Some distribution systems leaked, too.  Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't
make sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)

--

Adam
NY
2021-10-12 19:48:40 UTC
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Post by ARW
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains wires.
Too bad if you found out that the set was wrongly wired to the mains when
attempting to pull the Belling-Lee connector out of the back of the set.
Some distribution systems leaked, too. Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't make
sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)
"All receiver designs are obliged to maintain a d.c. path between the aerial
terminal and the chassis in order to drain off such a charge". I wonder how
well that worked in practice, if you were unlucky enough for the aerial to
be struck. I suppose it is there for lightning *prevention*, like the
mis-named lightning conductor on a building which is there to minimise the
chance of the metal roof etc being struck, but which probably can't handle
the huge current if it *is* struck.
ARW
2021-10-12 20:11:36 UTC
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Post by NY
Post by ARW
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains
wires. Too bad if you found out that the set was wrongly wired to the
mains when attempting to pull the Belling-Lee connector out of the
back of the set.
Some distribution systems leaked, too.  Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't
make sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)
"All receiver designs are obliged to maintain a d.c. path between the
aerial terminal and the chassis in order to drain off such a charge". I
wonder how well that worked in practice, if you were unlucky enough for
the aerial to be struck. I suppose it is there for lightning
*prevention*, like the mis-named lightning conductor on a building which
is there to minimise the chance of the metal roof etc being struck, but
which probably can't handle the huge current if it *is* struck.
More than 3 amps?

--

Adam
Peter Able
2021-10-12 19:50:07 UTC
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Post by NY
Post by ARW
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains
wires. Too bad if you found out that the set was wrongly wired to the
mains when attempting to pull the Belling-Lee connector out of the
back of the set.
Some distribution systems leaked, too.  Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't
make sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)
"All receiver designs are obliged to maintain a d.c. path between the
aerial terminal and the chassis in order to drain off such a charge". I
wonder how well that worked in practice, if you were unlucky enough for
the aerial to be struck. I suppose it is there for lightning
*prevention*, like the mis-named lightning conductor on a building which
is there to minimise the chance of the metal roof etc being struck, but
which probably can't handle the huge current if it *is* struck.
Red herring time! It worked - but it never was intended to deal with
direct strikes. What is?

PA
Rod Speed
2021-10-12 22:07:26 UTC
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Post by Peter Able
Post by NY
Post by ARW
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains
wires. Too bad if you found out that the set was wrongly wired to the
mains when attempting to pull the Belling-Lee connector out of the back
of the set.
Some distribution systems leaked, too. Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't
make sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)
"All receiver designs are obliged to maintain a d.c. path between the
aerial terminal and the chassis in order to drain off such a charge". I
wonder how well that worked in practice, if you were unlucky enough for
the aerial to be struck. I suppose it is there for lightning
*prevention*, like the mis-named lightning conductor on a building which
is there to minimise the chance of the metal roof etc being struck, but
which probably can't handle the huge current if it *is* struck.
Red herring time! It worked - but it never was intended to deal with
direct strikes. What is?
What is done with TV and radio transmitters and now mobile bases.
Peeler
2021-10-12 23:07:36 UTC
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On Wed, 13 Oct 2021 09:07:26 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>
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tony sayer
2021-10-12 22:26:36 UTC
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In article <sk4ops$ghn$***@dont-email.me>, NY <***@privacy.invalid>
scribeth thus
Post by NY
Post by ARW
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains wires.
Too bad if you found out that the set was wrongly wired to the mains when
attempting to pull the Belling-Lee connector out of the back of the set.
Some distribution systems leaked, too. Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't make
sure that his only electrical contact was with the plug.
PA
I spelt aerial correctly:-)
"All receiver designs are obliged to maintain a d.c. path between the aerial
terminal and the chassis in order to drain off such a charge". I wonder how
well that worked in practice, if you were unlucky enough for the aerial to
be struck. I suppose it is there for lightning *prevention*, like the
mis-named lightning conductor on a building which is there to minimise the
chance of the metal roof etc being struck, but which probably can't handle
the huge current if it *is* struck.
Yes there is IIRC something like 2 meg ohms that will have a path to
drain off any static charges from an aerial installation but if its
struck then thats is an insignificance on the scale of things.

Best bet if you know there is a storm about is to unplug the aerial lead
and drop it on the floor away from the TV not perfect but lightning
contains very large voltages and currents and can and does cause a lot
of damage even nearby strikes let alone direct ones.

Fix up a lightning conductor system if you like, got one here under
construction as its been for bloody years !...


Need some earth rods and a down conductor usually ally tape around 25 mm
wide and 4 mill thick much cheaper than copper!..

The idea is to shunt all the mega volts and amps past what you want to
be protected..


https://www.gca.co.uk/circuit-protection/earth-rods-accessories

https://www.gca.co.uk/circuit-protection/aluminium-conductors

https://www.electriccable.co.uk/RWDearthcableaccessTECC.php
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Brian Gaff (Sofa)
2021-10-13 07:51:08 UTC
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No all aerial sockets had insulation capacitors in them to stop getting a
severe shock. This was due to use of autotransformers or droppers rather
than total isolation by a proper transformer.
I could not read the doc as it was a picture, but I do know that its not
just TVs, FM/DAB tuners are also affected if its too close.
Its just a risk. I have over 150 metres of short wave aerials here and
only in very bad storms would I unplug them from the receiver. Modern front
ends are more durable lets say than the early transistor or fet ones were,
but not as hardy as valves of course!

Brian
--
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
***@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
Post by Peter Able
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
Dodgy things whether there's lightning - or even lightening - about, or not.
At that time, the chassis was often connected to one of the mains wires.
Too bad if you found out that the set was wrongly wired to the mains when
attempting to pull the Belling-Lee connector out of the back of the set.
Some distribution systems leaked, too. Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
That's for the metal-shell Belling-Lees - and for the guy who didn't make
sure that his only electrical contact was with the plug.
PA
tony sayer
2021-10-13 08:08:01 UTC
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Post by Brian Gaff (Sofa)
No all aerial sockets had insulation capacitors in them to stop getting a
severe shock. This was due to use of autotransformers or droppers rather
than total isolation by a proper transformer.
I could not read the doc as it was a picture, but I do know that its not
just TVs, FM/DAB tuners are also affected if its too close.
Its just a risk. I have over 150 metres of short wave aerials here and
only in very bad storms would I unplug them from the receiver. Modern front
ends are more durable lets say than the early transistor or fet ones were,
but not as hardy as valves of course!
Brian
Thats one reason why the Russians used them in their Aircraft radios,
they had great immunity to the EMP caused by Nuclear bomb
detonations!!!..

https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Peter Able
2021-10-13 17:51:55 UTC
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Post by Brian Gaff (Sofa)
No all aerial sockets had insulation capacitors in them to stop getting a
severe shock. This was due to use of autotransformers or droppers rather
than total isolation by a proper transformer.
Oh no they didn't. At that time there were plenty of universal TVs with
the Belling-Lee bolted directly to the chassis. Likewise your second
sentence.

PA
tony sayer
2021-10-13 19:49:35 UTC
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In article <sk79sc$7be$***@dont-email.me>, Peter Able <***@home.com>
scribeth thus
Post by Peter Able
Post by Brian Gaff (Sofa)
No all aerial sockets had insulation capacitors in them to stop getting a
severe shock. This was due to use of autotransformers or droppers rather
than total isolation by a proper transformer.
Oh no they didn't. At that time there were plenty of universal TVs with
the Belling-Lee bolted directly to the chassis. Likewise your second
sentence.
PA
Can you name any sets that did that, and what years were they in
service?...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Peter Able
2021-10-13 21:14:42 UTC
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Post by tony sayer
scribeth thus
Post by Peter Able
Post by Brian Gaff (Sofa)
No all aerial sockets had insulation capacitors in them to stop getting a
severe shock. This was due to use of autotransformers or droppers rather
than total isolation by a proper transformer.
Oh no they didn't. At that time there were plenty of universal TVs with
the Belling-Lee bolted directly to the chassis. Likewise your second
sentence.
PA
Can you name any sets that did that, and what years were they in
service?...
No, I just got given TVs - just about all of them universal - in the 50s
and 60s I could strip for components. The Belling-Lee sockets were
bolted using PK screws - to the chassis.

PA
williamwright
2021-10-14 00:40:29 UTC
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Post by tony sayer
Post by Peter Able
Oh no they didn't. At that time there were plenty of universal TVs with
the Belling-Lee bolted directly to the chassis. Likewise your second
sentence.
PA
Can you name any sets that did that, and what years were they in
service?...
I don't remember any tellys that didn't have isolating caps in the
aerial socket.

Bill
tony sayer
2021-10-14 12:19:40 UTC
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Post by williamwright
Post by tony sayer
Post by Peter Able
Oh no they didn't. At that time there were plenty of universal TVs with
the Belling-Lee bolted directly to the chassis. Likewise your second
sentence.
PA
Can you name any sets that did that, and what years were they in
service?...
I don't remember any tellys that didn't have isolating caps in the
aerial socket.
Bill
Me neither, they may have looked as if they bolted to the chassis but
the aerial connector was, as I've always remembered it to be, on a bit
of paxolin or SBRP board invariably with a couple of caps and resistors.

I think that very early TV's that had a mains input transformer and they
did exist then the chassis was earthed via three core cable but this
would have been a very long time ago now!...

Course these days you'd be a wanting to use one of the old Russ's aerial
cables, a snip at £169 for a couple of meters and for a further 15 quid
you can have them pre "burnt in"!


https://www.russandrews.com/v30aerial-cable-f-coax/
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
williamwright
2021-10-14 00:37:34 UTC
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Post by Peter Able
Some distribution systems leaked, too.  Then you'd be zapped at the
instant that the Belling-Lee disconnected from the TV.
A tenant with mental health problems connected mains to the TV socket.
His wallplate wasn't an isolated one thanks to the landlord sending an
electrician to replace it after the tenant had smashed it. It all came
to my attention when the system stopped working. The head end was in
another tenant's loft (WRONG WRONG WRONG) and was powered via a thin
flex to a 13A outlet in the heating duct. No earth bonding. The earth
conductor in the flex had got very hot and had melted the whole length
of the flex. Eventually this had shorted the cable out so the fuse in
the plug top had blown. It was alarming because the joists were scorched
and a bag of Christmas decorations had been on fire. Luckily the fire
had burnt out. The house had a young family in it.

Bill
Brian Gaff (Sofa)
2021-10-13 07:46:37 UTC
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Well, the problem always has been one of how close a lightning strike must
be to make any difference. I remember some time ago back in the analogue
days, there was an aerial which was effectively a stack of little dipoles
with a large reflector behind them, was it called the colour king or
something like that?

The anecdotal evidence suggested more TV tuners died using them than with
traditional yagi or logs. I always presumed that this was maybe due to the
dc circuit of a normal aerial was short circuit, but not of the dipole kind.
Also anywhere fringe where aerial amps on the mast were used, particularly
the early ally can Antiference ones, tended to get the amp trashed at the
slightest hint of a storm. I blue up three myself attempting to get
Hannington from Surrey.

So the answer is, if you want to, pull the aerial out but its not going to
save any active devices like masthead amps oar distribution amps still in
the system.
There do seem to be some places where a lot of lightning damage occurs,
some of the WElsh Valleys for example. Also a lot of cable boxes die where
TV services have overhead lines when there are storms.
Brian
--
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
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Blind user, so no pictures please
Note this Signature is meaningless.!
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
--
Adam
charles
2021-10-13 09:14:24 UTC
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Post by Brian Gaff (Sofa)
Well, the problem always has been one of how close a lightning strike
must be to make any difference. I remember some time ago back in the
analogue days, there was an aerial which was effectively a stack of
little dipoles with a large reflector behind them, was it called the
colour king or something like that?
it ws indeeed the Colour King made - by Wolsey. It had 4 double dipoles.
The Cour Prince had only 2. They were wideband aerials with a good F/B
ratio.
--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
tony sayer
2021-10-13 13:39:41 UTC
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Post by charles
Post by Brian Gaff (Sofa)
Well, the problem always has been one of how close a lightning strike
must be to make any difference. I remember some time ago back in the
analogue days, there was an aerial which was effectively a stack of
little dipoles with a large reflector behind them, was it called the
colour king or something like that?
it ws indeeed the Colour King made - by Wolsey. It had 4 double dipoles.
The Cour Prince had only 2. They were wideband aerials with a good F/B
ratio.
Can't see for the life of me how that would "attract" a lightning
discharge more than any other aerial unless there were just a lot of
those fitted in the area?...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Harry Bloomfield, Esq.
2021-10-13 14:47:38 UTC
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Post by tony sayer
Can't see for the life of me how that would "attract" a lightning
discharge more than any other aerial unless there were just a lot of
those fitted in the area?...
They didn't atract the lightening, rather it was simply the electrical
field around it which caused the damage, the static charge.

The conventional TV antenna forms a folded dipole - so the screen and
the inner are connected together, so not much voltage can develope
between them.

This type of antenna is not folded, so no actual connection between the
screen and the inner, so any voltage which appears across it, will also
be across the TV's tuner.
tony sayer
2021-10-14 11:49:39 UTC
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Post by Harry Bloomfield, Esq.
Post by tony sayer
Can't see for the life of me how that would "attract" a lightning
discharge more than any other aerial unless there were just a lot of
those fitted in the area?...
They didn't atract the lightening, rather it was simply the electrical
field around it which caused the damage, the static charge.
The conventional TV antenna forms a folded dipole - so the screen and
the inner are connected together, so not much voltage can develope
between them.
This type of antenna is not folded, so no actual connection between the
screen and the inner, so any voltage which appears across it, will also
be across the TV's tuner.
Don't think I've ever see a static discharge cause a problem nearby
lightning strikes yes, but not otherwise...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
tony sayer
2021-10-14 12:22:01 UTC
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Post by tony sayer
Don't think I've ever see a static discharge cause a problem nearby
lightning strikes yes, but not otherwise...
You have never felt the build up of static energy, during a
thunderstorm?
Well as IIRC you or was it Brian said they have a few hundred metres of
open wire feeders around haven't got that here!...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Harry Bloomfield, Esq.
2021-10-14 12:34:02 UTC
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Post by tony sayer
Well as IIRC you or was it Brian said they have a few hundred metres of
open wire feeders around haven't got that here!...
It wasn't me that said that, but yes I do have some very long wires
around here.

Peeler
2021-10-13 17:45:29 UTC
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On Thu, 14 Oct 2021 04:31:01 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>
--
Xeno to senile Rodent:
"You're a sad old man Rod, truly sad."
MID: <***@mid.individual.net>
tony sayer
2021-10-14 12:24:43 UTC
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Post by tony sayer
Post by charles
Post by Brian Gaff (Sofa)
Well, the problem always has been one of how close a lightning strike
must be to make any difference. I remember some time ago back in the
analogue days, there was an aerial which was effectively a stack of
little dipoles with a large reflector behind them, was it called the
colour king or something like that?
it ws indeeed the Colour King made - by Wolsey. It had 4 double dipoles.
The Cour Prince had only 2. They were wideband aerials with a good F/B
ratio.
Can't see for the life of me how that would "attract" a lightning
discharge more than any other aerial unless there were just a lot of
those fitted in the area?...
He wasn’t saying that it would. He is claiming that a folded
dipole presents a DC short circuit to the front end of the TV
so that static build-up during a big storm isn't a problem.
And i can't think of a UHF TV tuner that doesn't have a DC short in a
low ohms impedance tapping on a 1/4 wave input section!..

Even if the aerial isolator has been bypassed!..
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
williamwright
2021-10-14 00:43:35 UTC
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Post by charles
it ws indeeed the Colour King made - by Wolsey. It had 4 double dipoles.
The Cour Prince had only 2. They were wideband aerials with a good F/B
ratio.
The only use I found for them came from the fact that for V Pol use they
could help with ghosting. H Pol; no.

Bill
Martin Brown
2021-10-13 08:16:25 UTC
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Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
I have known my TV aerial lead to have enough potential on it to light
my neon screwdriver and just about feel it as a little nip touching it.
It was the latter that had me reaching for the neon screwdriver.

I guess there is sufficient capacitance in the coax downlead to store
enough energy to actually feel it.

There was a thunderstorm later on that day. Perhaps not the best time to
have been tweaking an aerial but there you go...

I'd expect old valve based sets to be fairly tolerant of lightning. I am
less confident about the outcome for modern solid state fet front ends.
Generally I have found lightning protection wanting in all the
situations where a building I was in took a direct hit. The chunky surge
arresters saved themselves by allowing more delicate line drivers to be
destroyed in the main computer - not the intention of having them at all :(
--
Regards,
Martin Brown
Mark Carver
2021-10-13 08:23:18 UTC
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Post by Martin Brown
I'd expect old valve based sets to be fairly tolerant of lightning. I
am less confident about the outcome for modern solid state fet front ends.
I've lost three masthead amp transistors in my time due to lightning
(BFR-90 from memory)

They may well have saved the telly itself from EMP damage
Sysadmin
2021-10-13 08:28:06 UTC
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Post by Martin Brown
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
I have known my TV aerial lead to have enough potential on it to light
my neon screwdriver and just about feel it as a little nip touching it.
It was the latter that had me reaching for the neon screwdriver.
I guess there is sufficient capacitance in the coax downlead to store
enough energy to actually feel it.
There was a thunderstorm later on that day. Perhaps not the best time to
have been tweaking an aerial but there you go...
I'd expect old valve based sets to be fairly tolerant of lightning. I am
less confident about the outcome for modern solid state fet front ends.
Generally I have found lightning protection wanting in all the
situations where a building I was in took a direct hit. The chunky surge
arresters saved themselves by allowing more delicate line drivers to be
destroyed in the main computer - not the intention of having them at all :(
There is in a cathode ray tube (~500pf)
NY
2021-10-13 09:29:26 UTC
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I have known my TV aerial lead to have enough potential on it to light my
neon screwdriver and just about feel it as a little nip touching it. It
was the latter that had me reaching for the neon screwdriver.
I had more than "a little nip" when I unplugged an aerial cable from a tuner
that was connected to my (earthed) PC, while touching the PC case with my
other hand. I eventually tracked it down to my TV which was on another leg
of the aerial cable (loft-mounted amplifier and splitter - unearthed). There
were a lot of culprits to check because my VCR was connected by phono cable
to my hifi, and all these devices were unearthed (double insulated).

When I measured the voltage on the screen of TV's aerial socket wrt ground,
it was about 130 V (!). There was evidently a large resistor, because when I
added a "human-sized" resistor where my body would have been (*) if I'd had
mains earth in one hand and aerial cable screen in the other, the voltage
dropped to about 50 V - still enough to give a fairly strong jolt when
you're not expecting it.

I added a wire from the earth pin of the amplifier to the screen of the
aerial cable (just one earth point, to avoid hum loops) to make sure the
TV's aerial/phono screen was grounded.

This was a modern TV - I bought it new in 2000 - so it wasn't one of those
ancient TVs with a live chassis. I was very underwhelmed with the reply I
got from Panasonic when I reported the problem: 130 V no-load voltage on a
part of the TV that the customer might touch, reducing to 50 V with a human
load, was not what I would regard as a safe design. I did check that the
plug was correctly wired, and that live and neutral hadn't got swapped.


(*) The shock was strong enough that I didn't want to repeat it, even as
part of the test!
Harry Bloomfield, Esq.
2021-10-13 10:05:14 UTC
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Post by NY
When I measured the voltage on the screen of TV's aerial socket wrt ground,
it was about 130 V (!). There was evidently a large resistor, because when I
added a "human-sized" resistor where my body would have been (*) if I'd had
mains earth in one hand and aerial cable screen in the other, the voltage
dropped to about 50 V - still enough to give a fairly strong jolt when you're
not expecting it.
I'm not surprised you got no joy from Panasonic, you will find that
almost all domestic TV's do have ac connection to the antenna socket,
via a capacitor.
charles
2021-10-13 11:10:05 UTC
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Permalink
Post by Harry Bloomfield, Esq.
Post by NY
When I measured the voltage on the screen of TV's aerial socket wrt
ground, it was about 130 V (!). There was evidently a large resistor,
because when I added a "human-sized" resistor where my body would have
been (*) if I'd had mains earth in one hand and aerial cable screen in
the other, the voltage dropped to about 50 V - still enough to give a
fairly strong jolt when you're not expecting it.
I'm not surprised you got no joy from Panasonic, you will find that
almost all domestic TV's do have ac connection to the antenna socket,
via a capacitor.
I found that on mine some years ago. Using a decent multimeter I found
about 30uA to ground.
--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
Harry Bloomfield, Esq.
2021-10-13 12:55:37 UTC
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Post by charles
I found that on mine some years ago. Using a decent multimeter I found
about 30uA to ground.
Just enough for the slightest of tickles..
Martin Brown
2021-10-13 10:51:28 UTC
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Post by NY
Post by Martin Brown
I have known my TV aerial lead to have enough potential on it to light
my neon screwdriver and just about feel it as a little nip touching
it. It was the latter that had me reaching for the neon screwdriver.
I had more than "a little nip" when I unplugged an aerial cable from a
tuner that was connected to my (earthed) PC, while touching the PC case
with my other hand. I eventually tracked it down to my TV which was on
another leg of the aerial cable (loft-mounted amplifier and splitter -
unearthed). There were a lot of culprits to check because my VCR was
connected by phono cable to my hifi, and all these devices were
unearthed (double insulated).
When I measured the voltage on the screen of TV's aerial socket wrt
ground, it was about 130 V (!). There was evidently a large resistor,
because when I added a "human-sized" resistor where my body would have
been (*) if I'd had mains earth in one hand and aerial cable screen in
the other, the voltage dropped to about 50 V - still enough to give a
fairly strong jolt when you're not expecting it.
I added a wire from the earth pin of the amplifier to the screen of the
aerial cable (just one earth point, to avoid hum loops) to make sure the
TV's aerial/phono screen was grounded.
This was a modern TV - I bought it new in 2000 - so it wasn't one of
those ancient TVs with a live chassis. I was very underwhelmed with the
reply I got from Panasonic when I reported the problem: 130 V no-load
voltage on a part of the TV that the customer might touch, reducing to
50 V with a human load, was not what I would regard as a safe design. I
did check that the plug was correctly wired, and that live and neutral
hadn't got swapped.
Some TV's like Freesat ones provide phantom power for the LNB but I'd
have expected something more like 12-24v no load maximum. I remember the
days of live chassis mains TVs full of glowing valves and in the back of
colour sets a hefty EHT rectifier that would double as an X-ray tube!
--
Regards,
Martin Brown
Harry Bloomfield, Esq.
2021-10-13 12:58:37 UTC
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Post by Martin Brown
a hefty EHT rectifier that would double as an X-ray tube!
Lots of volts, but very little actual current. One of my party tricks
was to stick a finger close to the EHT and draw out a long arc.
tony sayer
2021-10-13 13:37:26 UTC
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Post by Harry Bloomfield, Esq.
Post by Martin Brown
a hefty EHT rectifier that would double as an X-ray tube!
Lots of volts, but very little actual current. One of my party tricks
was to stick a finger close to the EHT and draw out a long arc.
With your finger or holding an insulated screwdriver?....
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Harry Bloomfield, Esq.
2021-10-13 14:34:34 UTC
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Post by tony sayer
With your finger or holding an insulated screwdriver?....
Finger!
tony sayer
2021-10-13 19:48:34 UTC
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Post by Harry Bloomfield, Esq.
Post by tony sayer
With your finger or holding an insulated screwdriver?....
Finger!
Now lets see a demo off say a 25 kV rail line system;)....
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Harry Bloomfield, Esq.
2021-10-14 12:01:07 UTC
Reply
Permalink
Post by tony sayer
Now lets see a demo off say a 25 kV rail line system;)....
--
The essential difference, is the amount of current behind it.
NY
2021-10-13 09:37:13 UTC
Reply
Permalink
Generally I have found lightning protection wanting in all the situations
where a building I was in took a direct hit. The chunky surge arresters
saved themselves by allowing more delicate line drivers to be destroyed in
the main computer - not the intention of having them at all :(
The only time I've suffered lightning damage was to the power supply for my
PC. And that was due to a lightning strike about a mile away (judging by the
5-second delay between lightning flash and very loud bang). So it was via
mains rather than through aerial, and was a strike on an EHT pylon, so it
had come via several step-down transformers.

I happened to have a spare PSU, and I had the old one disconnected and
removed, and the new one in place and connected, and the PC booted up again,
all within the 10-minute gap between one reading and the next from my
weather station which the PC was logging.

I doubt whether any form of surge protection will protect against a direct
lightning strike (*), but it should remove the sort of spikes that a
lightning strike on a distant power line can cause.

(*) eg to an overhead 240 V mains supply wire from street to house
Harry Bloomfield, Esq.
2021-10-13 10:19:29 UTC
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Post by NY
The only time I've suffered lightning damage was to the power supply for my
PC. And that was due to a lightning strike about a mile away (judging by the
5-second delay between lightning flash and very loud bang). So it was via
mains rather than through aerial, and was a strike on an EHT pylon, so it had
come via several step-down transformers.
There was a major strike 100 yards from here, which hit the church
spire. It blew their conductor out, then tracked down the spire doing
considerable damage to the plaster work inside.

Here the surge took out my sat systems front end, a modem, an
electronic phone, answering machine, plus some other minor items.
Locally, it damaged several phone lines too- BT spent a week up and
down the street repairing the damage.
tony sayer
2021-10-13 13:50:00 UTC
Reply
Permalink
Post by Harry Bloomfield, Esq.
Post by NY
The only time I've suffered lightning damage was to the power supply for my
PC. And that was due to a lightning strike about a mile away (judging by the
5-second delay between lightning flash and very loud bang). So it was via
mains rather than through aerial, and was a strike on an EHT pylon, so it had
come via several step-down transformers.
There was a major strike 100 yards from here, which hit the church
spire. It blew their conductor out, then tracked down the spire doing
considerable damage to the plaster work inside.
Here the surge took out my sat systems front end, a modem, an
electronic phone, answering machine, plus some other minor items.
Locally, it damaged several phone lines too- BT spent a week up and
down the street repairing the damage.
Church conductor can't have been much cop!, sure it had one and Mr Pikey
hadn't nicked it as it does happen!...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
Harry Bloomfield, Esq.
2021-10-13 14:38:25 UTC
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Post by tony sayer
Church conductor can't have been much cop!, sure it had one and Mr Pikey
hadn't nicked it as it does happen!...
I went down to take a look, it had completely blasted away. It was a
'elluva thump at 2am, I was fast asleep and shot in the air - left the
bed.
Rod Speed
2021-10-13 17:34:04 UTC
Reply
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Post by tony sayer
Post by Harry Bloomfield, Esq.
Post by NY
The only time I've suffered lightning damage was to the power supply for my
PC. And that was due to a lightning strike about a mile away (judging by the
5-second delay between lightning flash and very loud bang). So it was via
mains rather than through aerial, and was a strike on an EHT pylon, so it had
come via several step-down transformers.
There was a major strike 100 yards from here, which hit the church
spire. It blew their conductor out, then tracked down the spire doing
considerable damage to the plaster work inside.
Here the surge took out my sat systems front end, a modem, an
electronic phone, answering machine, plus some other minor items.
Locally, it damaged several phone lines too- BT spent a week up and
down the street repairing the damage.
Church conductor can't have been much cop!, sure it had one and Mr Pikey
hadn't nicked it as it does happen!...
If it had been nicked, there wouldn’t have been the plaster damage.
Peeler
2021-10-13 17:46:27 UTC
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On Thu, 14 Oct 2021 04:34:04 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>
--
"Anonymous" to trolling senile Rodent Speed:
"You can fuck off as you know less than pig shit you sad
little ignorant cunt."
MID: <***@haph.org>
Martin Brown
2021-10-13 15:57:13 UTC
Reply
Permalink
Post by Harry Bloomfield, Esq.
Post by NY
The only time I've suffered lightning damage was to the power supply
for my PC. And that was due to a lightning strike about a mile away
(judging by the 5-second delay between lightning flash and very loud
bang). So it was via mains rather than through aerial, and was a
strike on an EHT pylon, so it had come via several step-down
transformers.
There was a major strike 100 yards from here, which hit the church
spire. It blew their conductor out, then tracked down the spire doing
considerable damage to the plaster work inside.
Plaster was likely damp enough to generate steam then. You should see
what a direct hit that goes inside a tree does to it.
Post by Harry Bloomfield, Esq.
Here the surge took out my sat systems front end, a modem, an electronic
phone, answering machine, plus some other minor items. Locally, it
damaged several phone lines too- BT spent a week up and down the street
repairing the damage.
Had one close enough ~100m to me during the summer that there was a
sharp spark from my modem line before the power went out and big bang
arrived. Amazingly nothing was fried here. Neighbours lost mains alarm
clocks, the odd computer and modems though. I was lucky that time.

I was sure mine would be dead since I saw a fat calorific spark jump
from it to ground. So much for line protection OTOH maybe it worked!
--
Regards,
Martin Brown
tony sayer
2021-10-13 13:48:45 UTC
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Post by Martin Brown
Post by ARW
Just I have in my hand a 1964 copy of Aerial Handbook.
And it has this to say
http://wiki.diyfaq.org.uk/index.php/File:Aerialhandbook.jpg
maybe we need Bill's opinion.
I have known my TV aerial lead to have enough potential on it to light
my neon screwdriver and just about feel it as a little nip touching it.
It was the latter that had me reaching for the neon screwdriver.
I guess there is sufficient capacitance in the coax downlead to store
enough energy to actually feel it.
There was a thunderstorm later on that day. Perhaps not the best time to
have been tweaking an aerial but there you go...
I'd expect old valve based sets to be fairly tolerant of lightning. I am
less confident about the outcome for modern solid state fet front ends.
Generally I have found lightning protection wanting in all the
situations where a building I was in took a direct hit. The chunky surge
arresters saved themselves by allowing more delicate line drivers to be
destroyed in the main computer - not the intention of having them at all :(
Years ago we had some supposed TV repairers AKA as Cowboys do away with
the aerial isolator panel and by pass it so that if the TV twin flex was
arse about tit connected than the aerial was at 240 volts full mains!..

Great fun if you were a rigger! imagine grabbing hold of the aerial and
your earthed roof ladder tied to the two or three section ladder on a
damp lawn..

Always told the riggers to brush the back of their hand on the mast to
see if there was that sort of mains "Fuzz" before putting your hand
round to grip it. Any fuzz then stop work, unplug the TV and call one
the engineers out right away, no messing!...
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.
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