dodgy lamp affecting DTV

In message , Graham
writes

"tim....." wrote in message
...
When I go into my bedroom and turn on the lights one of the bulbs
flickers.

As it does this, my DTV reception breaks up (I can hear the sound
break up).

I've tested it a dozen times now, so I'm sure that the two events
are connected.

Whats; going on here?

I must make the observation that the OPs apparent difficulty in
believing that an outside electrical influence could affect his television
reception, is a testament to the immunity to interference that our
UHF negative-modulated with FM sound system has provided.

Contrast that to what preceded it.
http://www.bvws.org.uk/405alive/info...nterludes.html
(last item on the page)

Talking about 405-line TV, in the late 50s, every evening we had severe
interference on BBC TV (Ch5, Band 1). This took the form of a searing,
horizontal, narrow, stationary white line across the picture, and a loud
buzz on the sound. It started about 8pm, and went off at about 10pm, and
it made the picture essentially unwatchable. We usually had to switch
the TV off to save damage to tube.

By chance, I noticed that the interference coincided with the landing
light being on in a house two doors away. We approached the owners who,
although very friendly people, didn't seem to grasp what they were being
told, and saw no reason why they should change the lightbulb. They had a
TV of their own, but presumably didn't 'look in' as much we did in our
household. We were really getting fed up with things, but didn't really
want to spoil neighbourly relations by calling in the Post Office to
sort them out. Fortunately, about three weeks later, the interference
ceased. Discrete enquiries revealed that the lightbulb had failed, and
had been replaced.

The cause of this interference was probably a minute break in the
filament of the lightbulb. This arcs across, forming a type of
relaxation oscillator, with bursts of VHF oscillation synchronised to 50
or 100Hz (hence the interfering line was stationary). It is not common,
but the effects can be devastating.

A few years ago, I actually had a second case of similar interference
(this time to pre-digital analogue UHF TV). Fortunately, this time it
was my own light, which failed after a switch off - switch on.
Undoubtedly, it would have interfered with DTT.

Ian.
--

Talking about 405-line TV, in the late 50s, every evening we had severe
interference on BBC TV (Ch5, Band 1). This took the form of a searing,
horizontal, narrow, stationary white line across the picture, and a loud
buzz on the sound. It started about 8pm, and went off at about 10pm, and
it made the picture essentially unwatchable. We usually had to switch the
TV off to save damage to tube.

By chance, I noticed that the interference coincided with the landing
light being on in a house two doors away. We approached the owners who,
although very friendly people, didn't seem to grasp what they were being
told, and saw no reason why they should change the lightbulb. They had a
TV of their own, but presumably didn't 'look in' as much we did in our
household. We were really getting fed up with things, but didn't really
want to spoil neighbourly relations by calling in the Post Office to sort
them out. Fortunately, about three weeks later, the interference ceased.
Discrete enquiries revealed that the lightbulb had failed, and had been
replaced.

The cause of this interference was probably a minute break in the filament
of the lightbulb. This arcs across, forming a type of relaxation
oscillator, with bursts of VHF oscillation synchronised to 50 or 100Hz
(hence the interfering line was stationary). It is not common, but the
effects can be devastating.

A few years ago, I actually had a second case of similar interference
(this time to pre-digital analogue UHF TV). Fortunately, this time it was
my own light, which failed after a switch off - switch on. Undoubtedly, it
would have interfered with DTT.

I remember an ageing fluorescent tube in our kitchen causing severe
hum-bars on Holme Moss Ch2.

--
Graham.
%Profound_observation%

The cause of this interference was probably a minute break in the
filament of the lightbulb. This arcs across, forming a type of
relaxation oscillator, with bursts of VHF oscillation synchronised to 50
or 100Hz (hence the interfering line was stationary). It is not common,
but the effects can be devastating.

A few years ago, I actually had a second case of similar interference
(this time to pre-digital analogue UHF TV). Fortunately, this time it
was my own light, which failed after a switch off - switch on.
Undoubtedly, it would have interfered with DTT.

Ian.

Some fluorescent tubes radiate quite a bit in the UHF PMR bands!....
--
Tony Sayer

"tony sayer" wrote in message
news
The cause of this interference was probably a minute break in the
filament of the lightbulb. This arcs across, forming a type of
relaxation oscillator, with bursts of VHF oscillation synchronised to 50
or 100Hz (hence the interfering line was stationary). It is not common,
but the effects can be devastating.

A few years ago, I actually had a second case of similar interference
(this time to pre-digital analogue UHF TV). Fortunately, this time it
was my own light, which failed after a switch off - switch on.
Undoubtedly, it would have interfered with DTT.

Ian.

Some fluorescent tubes radiate quite a bit in the UHF PMR bands!....
--
Tony Sayer



Many forms of RFI can also knock seven bells out of ADSL connection speeds.
See some posts below.

Richard

"Graham" wrote in message
...

"tim....." wrote in message
...
When I go into my bedroom and turn on the lights one of the bulbs
flickers.

As it does this, my DTV reception breaks up (I can hear the sound
break up).

I've tested it a dozen times now, so I'm sure that the two events
are connected.

Whats; going on here?

I must make the observation that the OPs apparent difficulty in
believing that an outside electrical influence could affect his television
reception, is a testament to the immunity to interference that our
UHF negative-modulated with FM sound system has provided.

That's a very good point. But if DTT was to be transmitted at the same power
as analogue, and with massive error correction (only fair because each 8MHz
analogue slot only has one channel) would it still be a good point?

Contrast that to what preceded it.
http://www.bvws.org.uk/405alive/info...nterludes.html
(last item on the page)

When we fitted a car radio we used to cut each HT lead and fit in-line
ceramic things. They were just a high value resistor I believe.

In the days of the pirates I had an ex-army tank aerial on my van and it
used to be a bit scarey when I drove under the very low supergrid wires on
the A1 just north of Forte's near Barnsdale Bar. Those low wires are still
there by the way.

Bill

"Ian Jackson" wrote in message
...
By chance, I noticed that the interference coincided with the landing
light being on in a house two doors away.

We had one where the bulb only caused interference when the dimmer was set
below about half way. What's more, the bulb emitted a constant audio tone
(quite high) which co-incided exactly with the RF problem. It really was the
bulb and not the dimmer, as we proved by replacing it.

Bill

"Graham" wrote in message
...
I remember an ageing fluorescent tube in our kitchen causing severe
hum-bars on Holme Moss Ch2.

Yonks ago we had a big communal system wiped out by a sodium light on a
garage down the street. Every night after about 8pm. The aerial did point
towards the garage and the desired signals were exceedingly poor. I tracked
it down with an aerial and the analyser and tried to explain to the girl in
the filling station. Futile. I got the owner's phone number, and got told to
**** off. So I just got on their roof and smashed the bloody thing 'til it
went out. Bloke got onto the council and said he wanted his light paying for
so they threatened to contra charge him for all the time and hassle, so he
shut up.

Can't have my old grannies with no telly can I?

Bill

"Bill Wright" wrote in message
...

"Graham" wrote in message
...

"tim....." wrote in message
...
When I go into my bedroom and turn on the lights one of the bulbs
flickers.

As it does this, my DTV reception breaks up (I can hear the sound
break up).

I've tested it a dozen times now, so I'm sure that the two events
are connected.

Whats; going on here?

I must make the observation that the OPs apparent difficulty in
believing that an outside electrical influence could affect his
television
reception, is a testament to the immunity to interference that our
UHF negative-modulated with FM sound system has provided.

That's a very good point. But if DTT was to be transmitted at the same
power as analogue, and with massive error correction (only fair because
each 8MHz analogue slot only has one channel) would it still be a good
point?

Contrast that to what preceded it.
http://www.bvws.org.uk/405alive/info...nterludes.html
(last item on the page)

When we fitted a car radio we used to cut each HT lead and fit in-line
ceramic things. They were just a high value resistor I believe.

In the days of the pirates I had an ex-army tank aerial on my van and it
used to be a bit scarey when I drove under the very low supergrid wires on
the A1 just north of Forte's near Barnsdale Bar. Those low wires are still
there by the way.

That's the first time I've heard of an ex-army tank aerial being used as
anything other than a fishing rod )

Your post just reminded me there was an army surplus store selling those
things opposite where I lived 40 years ago. I had no recollection of it up
until then. Neither the store nor the place where I lived exists any more.

(kim)

"kim" wrote in message
...
"Bill Wright" wrote in message
...
That's the first time I've heard of an ex-army tank aerial being used as
anything other than a fishing rod )

I bought two, and I've still got the one I didn't use. It's been in my
garage for 40 years.

Bill

Mark Carver wrote:


I thought we use negative modulation, primarily because of the
linearity problems with early transmitter klystrons, using -ve mod the
bit of the video signal that would suffer most distortion are the sync
pulses, and not active picture. Or I might be totally wrong ?

Yes, you are correct and most are still in use!
A