Problems with Sat TV due to weather.
 

In article . com,
Mark Carver wrote:

charles wrote:
In article ,
Paul D.Smith wrote:

I have this fading memory that years ago 405 line VHF BBC1 from London
reached as far as Jo'burg in South Africa.

Since there was no tv in South Africa at the time, and even when there
was it didn't use Band I, I wonder how anybody noticed.

The story has been knocking about for years, it could well be an urban
myth, however perhaps the audio carrier was received ?

The Wiki page I quoted mentions reception of BBC 1 Holme Moss on Ch 2
in Perth Australia in 1979 however. Again no 405 TV service there.

and there was the well documented one the other way round. In parts of the
Ayrshire coast viewers received a test pattern from an American station.
Trouble was the station had shut down three years previously !

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Problems with Sat TV due to weather.
 

charles wrote:
In article . com,
Mark Carver wrote:
The Wiki page I quoted mentions reception of BBC 1 Holme Moss on Ch 2
in Perth Australia in 1979 however. Again no 405 TV service there.

and there was the well documented one the other way round. In parts of the
Ayrshire coast viewers received a test pattern from an American station.
Trouble was the station had shut down three years previously !


Perhaps the signal had bounced off a planet 1.5 light years away ?

--
Mark
Please replace invalid and invalid with gmx and net to reply.

Problems with Sat TV due to weather.
 

charles wrote:

and there was the well documented one the other way round. In parts of the
Ayrshire coast viewers received a test pattern from an American station.
Trouble was the station had shut down three years previously !

Long-delayed echoes, obviously :-)

This article lists many cases of extreme DX TV reception - mostly via
ionospheric modes in the low VHF (Sporadic-E and F2):
http://en.wikipedia.org/wiki/TV-FM_DX

Separate page about Sporadic-E he
http://en.wikipedia.org/wiki/Sporadic_E

--
Andy

Problems with Sat TV due to weather.
 

In article ,
Mark Carver wrote:
charles wrote:
In article . com,
Mark Carver wrote:
The Wiki page I quoted mentions reception of BBC 1 Holme Moss on Ch 2
in Perth Australia in 1979 however. Again no 405 TV service there.

and there was the well documented one the other way round. In parts of
the Ayrshire coast viewers received a test pattern from an American
station. Trouble was the station had shut down three years previously !


Perhaps the signal had bounced off a planet 1.5 light years away ?

or had been recorded by visitors from outer space and played back on their
next visit ?

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Problems with Sat TV due to weather.
 

"Mark Carver" wrote in message
ups.com...

charles wrote:
In article ,
Paul D.Smith wrote:

I have this fading memory that years ago 405 line VHF BBC1 from London
reached as far as Jo'burg in South Africa.

Since there was no tv in South Africa at the time, and even when there
was
it didn't use Band I, I wonder how anybody noticed.

The story has been knocking about for years, it could well be an urban
myth, however perhaps the audio carrier was received ?

Most certainly, in the 60's I used to listen to BBC sound on 40.50MHz
(video being on 45 MHz)

A frequency that cetainly could reach South Africa at sunspot peak,
or more likely multiple sporadic E in summer

Steve Terry

Problems with Sat TV due to weather.
 

I have this fading memory that years ago 405 line VHF BBC1 from London
reached as far as Jo'burg in South Africa.

Since there was no tv in South Africa at the time, and even when there was
it didn't use Band I, I wonder how anybody noticed.

When did South Africa get TV then? This was shortly before 405 closed down
and the news item (BBC news) also mentioned something about the London
transmitter using an unsual bandwidth, something about it being old whereas
newer transmitters were somehow more efficient - but I was young so the
details are missing I'm afraid.

Paul DS.

Problems with Sat TV due to weather.
 

Paul D.Smith wrote:
I have this fading memory that years ago 405 line VHF BBC1 from London
reached as far as Jo'burg in South Africa.

Since there was no tv in South Africa at the time, and even when there was
it didn't use Band I, I wonder how anybody noticed.

When did South Africa get TV then?

I think SABC started their TV service as late as 1975 ?

This was shortly before 405 closed down
and the news item (BBC news) also mentioned something about the London
transmitter using an unsual bandwidth, something about it being old whereas
newer transmitters were somehow more efficient - but I was young so the
details are missing I'm afraid.

The old Ally Pally BBC TV transmitter used double sideband
transmission, all subsequent 405 and 625 line txs have used vestigial
sidebands, and I think this included Crystal Palace 405 when the move
to there was made in the 50s ?

http://en.wikipedia.org/wiki/Vestigal_sideband

Problems with Sat TV due to weather.
 

In article , Paul D.Smith
wrote:
I have this fading memory that years ago 405 line VHF BBC1 from London
reached as far as Jo'burg in South Africa.

Since there was no tv in South Africa at the time, and even when there
was it didn't use Band I, I wonder how anybody noticed.

When did South Africa get TV then? This was shortly before 405 closed
down and the news item (BBC news) also mentioned something about the
London transmitter using an unsual bandwidth, something about it being
old whereas newer transmitters were somehow more efficient - but I was
young so the details are missing I'm afraid.

When Alexandra Palace opened in the 1930s it used double sideband
transmissions. All later services and London, when it moved to CP, used
single sideband. However the channel allocation for a double sideband
channel 1 still remained. CP opened in 1956 so at any date after that the
service had a normal bandwidth.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Problems with Sat TV due to weather.
 

"Mark Carver" wrote in message
...
Graculus wrote:

Trouble is, this kind of "weather" also affects digital terrestrial
broadcasts, too. Currently, it's analogue TV and FM all the way for me,
as Freeview signal has fallen to pretty mich nothing, and DAB error rate
is running at an impossible-to-listen-to 60+. All the waffle that they
come out with about digital being unaffected by weather is utter garbage.
Once we're all forced onto digital TV, will I get a TV licence refund for
every day like this when I'll be unable to receive any TV at all?

It'll be interesting to see. I think an unwanted analogue TV signal
landing on top of a wanted digital one, is more destructive than 'digital
on digital' ? Bill W will know from his experiences.

Of course after analogue switch off all our DTT transmissions will
increase in power, but it'll be the same in Europe, so back to square one
?

With analogue you can see the picture gradually getting worse during
periods such as this, with DTT there's a bit of pixelation then often
black and silence.

It's very difficult to quantify, but I can generalise wildly and say that
analogue co-channel effects have to be pretty annoying before DTT starts to
fall over. That's with the present set-up in which DTT powers are generally
low.

Come the revolution . . err sorry, the analogue switch-off . . . the DTT
powers will increase. This should give better protection against
interference from foreign analogue signals, all things being equal, but it
will amount to nothing more than an arms escalation regarding DTT/DTT
co-channel from the UK, or indeed I suppose from the mainland.

Bill

Problems with Sat TV due to weather.
 

"Alan Pemberton" wrote in message
erve.co.uk.invalid...
Mark Carver wrote:

charles wrote:
In article ,
Paul D.Smith wrote:
snip
There was some off-screen footage taken of 405-line Ally Pally
transmissions received in North America around 1936-39.

Alli Pally London on 45MHz, which is a frequency which
under the right conditions will travel the world

Steve Terry