Terrestrial Switchoff - sorry to labour the point but...

In message , Mark
Carver writes
hwh wrote:
My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)
Well, we Brits put the U in colour, and the frequency ;-)
In fact our first colour broadcast was on 10/10/1955 after the close of
service from Alexandria Palace in N.T.S.C. (Never Twice the Same
Colour).
It wasn't adopted because of the colour distortion caused by attenuation
of the sidebands in the sub-carrier. Phase Alternating Line was known
about as it was supposed to correct the errors by eye, but instead made
a nasty crawling dot pattern known as Hanover Blind and can be seen in
Simple PAL sets. PAL came into it's own when Telefunken perfected the
sum and difference effects of PAL using a glass delay line, with the
outcome that in the face of serious disorder in the signal, instead of
Hanover Blind all that happened was desaturation of the hue signal
presented to the CRT.
--
Clive

"Clive" wrote in message
...
In message , Jim Lesurf
writes
Ealier designs wore down, particularly if used
with tapes that were more abrasive. So measured well in a review, but
deteriorated swiftly in use.

Correct, mu-metal heads had a life expectance of 500 hours.

In the early days of domestic tape recorders the heads could be unplugged
and replaced.

--
Max Demian

On 3/29/13 6:09 PM, Mark Carver wrote:
hwh wrote:

My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)

Well, we Brits put the U in colour, and the frequency ;-)

Oops. Oh well. Don't start about elevators. Or aerials

gr, hwh

In message , Johny B Good
writes
If we could all have experienced the playback quality enjoyed by the
studio staff as a matter of routine in our homes, there wouldn't have
been any motivation to develop the audio CD technology in the first
place.
Dolby "B" which had to be used on cassette because of the very large
noise component, was just a vastly cut down from Dolby "A". B, only
increased the treble so that on reply cutting the treble by the same
amount to normalise took the noise with it. A, cut it down into I
think 6 different bands each with different treatment to give a much
superior (though more expensive) sound.
--
Clive

On Fri, 29 Mar 2013 17:21:20 +0000, Clive
wrote:

As I remember it, audio will not leave an imprint on the tape because of
the hysteresis which is needed to keep the recorded item on the tape.

Yes, this is something I do vaguely remember ...

A high frequency waveform is applied to the tape very much the same as a
Carrier wave carries signal from one place to another , the only
difference being that the carrier is modulated in an A.M. Radio, whereas
bias is used to "punch" the signal into the tape pass the hysteresis
boundary and is at a constant level set by the characteristics of the
tape.

Yes, the purpose of the 'carrier wave' bias was so that the recordings
could be made at magnetic intensity (IIRC?) levels where the
hysteresis characteristic of the recording tape was at its most linear
= less distortion in the played back result.
--
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In message , Clive
writes:
In message , Mark
Carver writes
hwh wrote:
My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)
Well, we Brits put the U in colour, and the frequency ;-)
In fact our first colour broadcast was on 10/10/1955 after the close of
service from Alexandria Palace in N.T.S.C. (Never Twice the Same
Colour).
It wasn't adopted because of the colour distortion caused by
attenuation of the sidebands in the sub-carrier. Phase Alternating
Line was known about as it was supposed to correct the errors by eye,
but instead made a nasty crawling dot pattern known as Hanover Blind
and can be seen in Simple PAL sets. PAL came into it's own when
Telefunken perfected the sum and difference effects of PAL using a
glass delay line, with the outcome that in the face of serious disorder
in the signal, instead of Hanover Blind all that happened was
desaturation of the hue signal presented to the CRT.

I don't think Hanover blind was a _dot_ crawl pattern as such, more a
pairing of lines with opposite colour errors.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)[email protected]+H+Sh0!:`)DNAf

Have you ever tried Chicken Tarka? It's like Chicken Tikka, only 'otter.

In article ,
J. P. Gilliver (John) wrote:
In message , Clive
writes:
In message , Mark
Carver writes
hwh wrote:
My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)
Well, we Brits put the U in colour, and the frequency ;-)
In fact our first colour broadcast was on 10/10/1955 after the close of
service from Alexandria Palace in N.T.S.C. (Never Twice the Same
Colour).
It wasn't adopted because of the colour distortion caused by
attenuation of the sidebands in the sub-carrier. Phase Alternating
Line was known about as it was supposed to correct the errors by eye,
but instead made a nasty crawling dot pattern known as Hanover Blind
and can be seen in Simple PAL sets. PAL came into it's own when
Telefunken perfected the sum and difference effects of PAL using a
glass delay line, with the outcome that in the face of serious disorder
in the signal, instead of Hanover Blind all that happened was
desaturation of the hue signal presented to the CRT.

I don't think Hanover blind was a _dot_ crawl pattern as such, more a
pairing of lines with opposite colour errors.

and usually known as "Hanover Bars"

--
From KT24

Using a RISC OS computer running v5.18

In article , Clive
writes
In message , Jim Lesurf
writes
The recording side is rather different as the 'trailing edge' of the field
being applied tends to 'wipe' what other parts previously imposed. Hence
the angled offset 'cross field' recording systems can have a smaller and
more controlled effective gap.
As I remember it, audio will not leave an imprint on the tape because
of the hysteresis which is needed to keep the recorded item on the
tape. A high frequency waveform is applied to the tape very much the
same as a Carrier wave carries signal from one place to another , the
only difference being that the carrier is modulated in an A.M. Radio,
whereas bias is used to "punch" the signal into the tape pass the
hysteresis boundary and is at a constant level set by the
characteristics of the tape.

I don't know where you got that lot from, but Jim's quite correct.

Bias is to make the transfer characteristic as linear as possible, and
I'm fairly certain machines without bias were used in the early days of
magnetic recording. They worked, just not very well. I think Marconi
Stille machines didn't use bias, but I may be wrong about that.

Hysteresis is a physical property of the recording medium, not something
you do to it.


--
SimonM

On Mar 29, 5:38*pm, Clive wrote:
In message , Mark
Carver writeshwh wrote:
My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)
Well, we Brits put the U in colour, and the frequency *;-)

In fact our first colour broadcast was on 10/10/1955 after the close of
service from Alexandria Palace in N.T.S.C. (Never Twice the Same
Colour).
It wasn't adopted because of the colour distortion caused by attenuation
of the sidebands in the sub-carrier. * Phase Alternating Line was known
about as it was supposed to correct the errors by eye, but instead made
a nasty crawling dot pattern known as Hanover Blind and can be seen in
Simple PAL sets. * PAL came into it's own when Telefunken *perfected the
sum and difference effects of PAL using a glass delay line, with the
outcome that in the face of serious disorder in the signal, instead of
Hanover Blind all that happened was desaturation of the hue signal
presented to the CRT.
I get the impression that you think that you understand PAL (and by
definition NTSC), so I'll keep it simple for you

Hanover lines are caused, in simple PAL, by a phase shift on alternate
lines leading a "venetian blind" effect on the image. Alternate lines,
when a phase error is present, swing alternately towards the red and
blue axes (as seen on a vectorscope), a delay line system will
effectively add the errors and display the difference between the two
(but given the way that the summation takes place, the saturation will
decrease at the cost of displaying the correct chroma phase).

The dot patterning to which I assume that you refer, is caused when
there is a fixed mathematical relationship between the CSC and line
frequencies. (283.75 in the original 625/50 PAL). Older readers may
know this frequency as (F)nat. The precision offset of 25Hz was added
resulting in (F)csc. The septics got round the same issue by changing
the Frame rate by 1% (hence 525/59.940.

In article
,
Curtis Interruptus wrote:
On Mar 29, 5:38 pm, Clive wrote:
In message , Mark
Carver writeshwh wrote:
My uncle was offered a 'color aerial' decades back. And yes, we
continentals had color on VHF ;-)
Well, we Brits put the U in colour, and the frequency ;-)

In fact our first colour broadcast was on 10/10/1955 after the close of
service from Alexandria Palace in N.T.S.C. (Never Twice the Same
Colour).
It wasn't adopted because of the colour distortion caused by attenuation
of the sidebands in the sub-carrier. Phase Alternating Line was known
about as it was supposed to correct the errors by eye, but instead made
a nasty crawling dot pattern known as Hanover Blind and can be seen in
Simple PAL sets. PAL came into it's own when Telefunken perfected the
sum and difference effects of PAL using a glass delay line, with the
outcome that in the face of serious disorder in the signal, instead of
Hanover Blind all that happened was desaturation of the hue signal
presented to the CRT.
I get the impression that you think that you understand PAL (and by
definition NTSC), so I'll keep it simple for you

Hanover lines are caused, in simple PAL, by a phase shift on alternate
lines leading a "venetian blind" effect on the image. Alternate lines,
when a phase error is present, swing alternately towards the red and
blue axes (as seen on a vectorscope), a delay line system will
effectively add the errors and display the difference between the two
(but given the way that the summation takes place, the saturation will
decrease at the cost of displaying the correct chroma phase).

The dot patterning to which I assume that you refer, is caused when
there is a fixed mathematical relationship between the CSC and line
frequencies. (283.75 in the original 625/50 PAL). Older readers may
know this frequency as (F)nat. The precision offset of 25Hz was added
resulting in (F)csc. The septics got round the same issue by changing
the Frame rate by 1% (hence 525/59.940.

they also had a problem with interference from the sound carrier which was
the main reason for the 1% change in frame rate. But, it's nearly 50 years
since I knew the maths.

--
From KT24

Using a RISC OS computer running v5.18