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Old 1st Feb 2007, 7:20 pm   #1
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Default Was 819 HDTV?

Split from Teleavia thread. https://www.vintage-radio.net/forum/...ad.php?t=14493

There were 2 flavours of 819, E and F. F (Belgium) had EQ pulses, E France) did not. Uniquely, E had a single broad pulse.

http://www.pembers.freeserve.co.uk/W...rds.html#Parts
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Old 1st Feb 2007, 8:10 pm   #2
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Default Re: Was 819 HDTV?

Admittedly, these are questions I could settle by going looking on the web , but (speaking off the top of my head) didn't the 819 system(s) have something like a 10MHz bandwidth and use odd, overlapping channels in Band III ?

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Old 1st Feb 2007, 8:47 pm   #3
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Default Re: Was 819 HDTV?

The (French) system E video bandwidth was at least 10MHz, the sound spacing was 11.15MHz in a 14MHz channel. I doubt if that full bandwidth was often realised, either at the studios or the receivers. It was clearly profligate in its use of bandwidth and this may have been one the resons for its demise.

The Belgian version (system F) must have looked poor by comparison since the video bandwidth was restricted to about 5MHz. This would have given much less horizontal resolution than the 625 system. Remember that for more lines you need more bandwidth, just to get the same horizontal resolution.
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Old 1st Feb 2007, 9:28 pm   #4
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Default Re: Was 819 HDTV?

The 819 line system in the 1950's was poor when compared with the British 405 line system. Our pictures were sharper and the French sets that I remember when on a school trip to France in 1960, appeared to have less contrast. I doubt if the scanning spot could be made small enough to exploit the system to the full with the tubes available at that time.
The 21" tube was very popular in France I believe but I doubt if the end result was much better than a 405 line set with 'spot wobble'. If the system had been retained, no doubt with modern equipment the results would probably have been outstanding. Regards John.
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Old 2nd Feb 2007, 12:30 am   #5
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Default Re: Was 819 HDTV?

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Originally Posted by Heatercathodeshort View Post
The 819 line system in the 1950's was poor when compared with the British 405 line system. Our pictures were sharper and the French sets that I remember when on a school trip to France in 1960, appeared to have less contrast. I doubt if the scanning spot could be made small enough to exploit the system to the full with the tubes available at that time.
I only saw 819 line TV once, in Brussels in the late 1960s, on a 14" portable. It was an episode of the Forsyte Saga dubbed into French. Picture was a bit snowy. I remember that I couldn't hear the line whistle.

Roughly speaking, you need 6MHz bandwidth on 819 to get the same horizontal resolution that is given by 3MHz on 405. By the 1960s the British 405 system had been fully exploited by the technology so it's not surprising that the pictures could look good. Shame about the mean level AGC (= Always Grey Control) and lack of black level clamping which meant that few sets showed the system at its best.

Although I don't have any solid evidence, I think that the CRT was a lesser problem for 819. Video and IF bandwidth along with signal to noise ratio must have been pretty tough to get right.
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Old 6th Feb 2007, 11:55 am   #6
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Default Re: Was 819 HDTV?

If the full potential of the the French 819 line television system was realised then it could be said that this was the worlds first true high definition system.

The bandwdth of a good set should be 10mhz, whether that could be realised in practise I'm not so sure.

The earlier TV sets employed three or four valves in the vision IF amplifier stages so it is likely those receivers were up to the job, but I notice the late fifties receivers often only employ two IF amplifier valves, just like UK 405 receivers. I guess on the later sets the max bandwidth will be only 6 to 7 mhz.
The valves used in most sets were common European types such as the EF80, receivers after 1960 would use frame grid pentodes, EF183 and EF184.

The RTF test card has frequency gratings for 9mhz so that must be the figure that one would like to attain when servicing a good set. I remember when the 3mhz bars on test card C were the ambition of service engineers during the 405 days.

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Old 8th Feb 2007, 10:48 pm   #7
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Default Re: Was 819 HDTV?

Hi,

For comparison, two HD resolutions are "1080", which is 1920 x 1080 pixels, and "720", which is 1280 x 720 pixels. These are both 16:9, though. The centre 4:3 section of these two comes out as 1440 x 1080 and 960 x 720 respectively.

The resolution I'm running my MythTV system for 819-line is 1152 x 738, as covered in this thread.

That falls neatly in between the two HD formats. So 819-line is HD. Case closed?

Cheers, Kat
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Old 9th Feb 2007, 9:01 am   #8
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Default Re: Was 819 HDTV?

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That falls neatly in between the two HD formats. So 819-line is HD. Case closed?
Not quite. There are plenty of people who will argue that the current 720p standards are not really HD. Also don't forget interlace. Research done by Kell et al many years ago showed that the perceived vertical resolution for a given number of lines was lower in interlaced systems than in progressive systems. This is the infamous Kell factor. If you take this into account then the 819 system (738 active, interlaced) falls below 720 progressive.

Despite this nit picking, I still believe that the French set out to create a real HD system at a time when even 405 was still regarded as HD. Remember that HD is a moveable goal. In 1935, anything over 200 lines was called HD. Now it's over 720.

The 819 system was a brave attempt which ultimately failed due to technology limitations. For once I don't think it was political considerations that led to its downfall. Assuming that improving technology would have allowed it to give its full performance, it was already crippled in Belgium due to narrow channels. The argument of more channels versus better pictures would have been overwhelming in the 1950s and 1960s.
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Old 9th Feb 2007, 10:22 pm   #9
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Default Re: Was 819 HDTV?

Certainly in theory the 819 line system was HDTV, but as has already been mentoned the pictures were rarely better than our 405 line system due to the limitations of the technology of the day. The pictures would of course have looked smoother, especially on larger screens, as the line spacing would have been much less than our 405 and the European 625 systems.
I would have loved to have seen an 819 line picture especially on a later 20/24" tv from the late 1960's or 1970's just to compare the quality against our 405 and 625 line pictures.
BTW the 625 line system was and still is hailed as high definition, this was one of the main points (as well as colour) that they were pushing during the early 1970's to urge more people to change over from 405.
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Old 15th Feb 2007, 8:11 pm   #10
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Default Re: Was 819 HDTV?

One of the 819 line television receivers I brought over from France last year is a compact 17" set made by by a firm called ITV.
This set will be ideal for conversion to a baseband monitor as it employs a fully isolated chassis, the mains transformer has proper isolated primary.
All the valves are 6.3 volt types, e.g. EL36, EY88, ECL82 etc.

The video output valve is an EL83 and 3 volts of video are required at the control grid for a fully contrasted picture. A video pre-amplifier will have to be constructed, I'll use transistors instead of valves as there is not much available space inside of the cabinet.

The set has a turret tuner but is only equiped with coils for channel 8A.
The IF amplifier uses three EF80s, one serves as a common vision and sound amplifier, the other two are in the vision IF amp. One EBF89 serves as the sound IF and detector.

The picures show the set and the special inverted magnet loudspeakers.

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Old 18th Feb 2007, 3:01 pm   #11
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Default Re: Was 819 HDTV?

Quote:
Originally Posted by Hybrid tellies View Post
Certainly in theory the 819 line system was HDTV, but as has already been mentoned the pictures were rarely better than our 405 line system due to the limitations of the technology of the day. The pictures would of course have looked smoother, especially on larger screens, as the line spacing would have been much less than our 405 and the European 625 systems.
I would have loved to have seen an 819 line picture especially on a later 20/24" tv from the late 1960's or 1970's just to compare the quality against our 405 and 625 line pictures.
BTW the 625 line system was and still is hailed as high definition, this was one of the main points (as well as colour) that they were pushing during the early 1970's to urge more people to change over from 405.
Interesting stuff. Though as I understand it, form the very early 70s on all 819 pictures were optically converted at the TX site from 625, resulting it pretty poor pics. Before that I heard they had two cameras in the studio, you guessed it one or two for 819 and the others for 625 lines because electronic converters for 819 were expensive/impractical.

Nowadays 525/625 is reffered to as SD in broadcast circles. HD is 720 lines upwards, though this is progressive scan of course as 1080 interlace is really only half that number of lines on the screen at anyone time. Most HD displays are flat plasma/LCD which are native progressive. I can see interlace becoming a thing of the past as now we have 1080 progressive cameras and displays which will work for sports programming which is what interlace is currently best for with HD. Afterall, interlace is not just motion smoothing but also a form of signal compression and flicker reduction, clever and simple though it is.

With 819 lines having good interlace in the set wouldn't have been noticable like on 405 lines. I wonder how many people were really watching 202.5 lines on their badly set up TVs and putting up with it!
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