Golborne Vintage Radio

If I was a French skinflint TV designer & wanted to make an 819/625 lines dual standard telly cheaply I 'd restrict the 819 bandwidth to about 6'ish MHZ as used for 625, so I could use the same IF gubbins for both systems & hope le public didn't notice the soft picture on 819 lines. Thing is did any french TV makers actually do this?

The Belgian public didn't have any choice in the matter. Their take on the 819 system was damaged at birth by use of narrow channels.

If anyone has a full BW 819 set there isn't a currently available source of full BW 819 pictures. All the Aurora converters are limited by the 625 line input. You'd need a minimum 720p HD input to approach full resolution. FWIW, 720p has very nearly as many active lines as 819 and commensurate horizontal resolution. 1080 HD is comfortably better than 819. This ignores any problem with aspect ratio. If you keep all the lines from an HD source you're losing a fair bit of H resolution. OK if starting from 1080 but not from 720.

This goes to show what a leap of faith 819 was. A leap that was taken a bit too early for the technology to catch up with the potential of the system.

I think that the answer to the original question is probably yes, at least for some of the cheaper receivers.

I have a couple of pertinent datapoints:

The first is from the monochrome single standard era:

[attachment=16354]

It shows that vision IF bandwidth was a published parameter for French TV receivers, with 9 and 10 MHz being common numbers.  Against that background and the expectations created, it may have been difficult to sell narrow bandwidth receivers other than at the bottom end of the market.

The second is from the early colour dual-standard era:

[attachment=16355]

This shows a division between the cheaper receivers, which used the same narrower bandwidth for 625 and 819, and the better-specified receivers, which used a 9 MHz bandwidth for 819.

I think it is reasonable to assume that early colour era practice was carried over from norms established during the monochrome dual-standard era.

Apparently for ease of receiver design, the French chose the 625-line IF so that the sound carrier was the same as for 819 lines, namely 39.2 MHz.  So a wideband vision IF would have a sound trap at 39.2 MHz, and at the lower end trapping to put the Nyquist slope -6 dB point at 28.05 MHz for 819, with switchable trapping to put the Nyquist slope -6 dB point at 33.7 MHz for 625.  With a narrow band vision IF, it would appear that one would need what was effectively a switchable centre tuning point.  For 625 the -6 dB points would need to be at 33.7 and say 39.7 MHz, for a centre frequency of 36.7 MHz.  Using the same bandwidth for 819 would put the -6 dB points at 28.05 and 34.05 MHz, for a centre frequency of 31.05 MHz.  So, some/all of the IFTs would need to have switchable tuning points.  It was different to the UK case, where “lazy” setmakers could use a double-Nyquist IF shape (allowing a 4.85 MHz vision bandwidth on 625) with switchable traps for 405.

Belgian four-standard receivers mostly used the same narrow IF bandwidth for French 819-line transmissions as they did for Belgian 819-lines, although there were some exceptions, according to this reference:

[attachment=16356]

When UHF arrived, some Belgian receivers at least used a 39.9 MHz vision IF for the French System L, as compared with 38.9 MHz for all others.  This allowed the System L sound IF to be at 33.4 MHz, the same as for Systems B/G/H, C and F.  So they probably could exploit the extra bandwidth of System L.

What was the practice for French Strasbourg/border area multistandard receivers I do not know.  But Is suspect that the French setmakers would have been inclined to treat favourably their own 819-line system.

A suitable case for study would be those rather very good Barco CRM2631 multistandard receiver-monitors from the 1970s.  They covered all but System A as I recall, and their general quality level would suggest that they would not have been majorly compromised in the vision bandwidth department.  (I am not sure if or how they handled the French Band I System E and System L’ channels, which were a bit of a problem for multistandard receivers.)  But circuit information on the CRM2631 seems to be unobtanium.

Cheers,
  
Steve

(21-06-2017, 02:25 PM)ppppenguin Wrote: [ -> ]If anyone has a full BW 819 set there isn't a currently available source of full BW 819 pictures. 

Assuming your modulator has the bandwidth I don't think there would be a problem generating it from a PC graphics card.

Peter

Quite right. I'd forgotten about the PC based methods. You still need an HD source so an ordinary DVD isn't good enough. Blu-ray or stored/streamed HD needed.

There's a number of 1950s 819line only TVs in the stockroom above the shop. Hurry while stocks last.

Geordie McBoyne.

http://www.vintage-radio.net/forum/showt...post953332

http://www.vintage-radio.net/forum/attac...tid=144980&d=1498242807

I'm thinking a Belgian 4 standard telly would have been a very complicated thing. It'd have to receive 625 lines 5 MHz negative video with FM sound, 625 lines 5 MHz positive video with AM sound with pre-emphasis, 819 lines 5 MHz positive video with AM sound with pre-emphasis (I think) & 819 lines 9/10 MHz positive video with AM sound with no pre-emphasis. It's making my head spin just thinking about it. I suppose they could have made it a bit simpler by restricting the French 819 bandwidth to 5 MHz, & of course Mr & Mrs Belgian Public would be used to a soft 819 picture..

Possibly the major difficulty with providing full or nearly full vision bandwidth for the French 819-line system would have been the resultant loss of IF gain, probably requiring another amplification stage.  Switching might not have been so difficult.  With a wideband IF strip, the lower limit for French 819 would have been defined by the sound trap at 27.75 MHz.  Then the 33.4 MHz sound trap (and 31.9 MHz adjacent channel vision trap) would have been switched in for the Belgian 819 and both 625 line systems, narrowing the IF strip input bandwidth, but not changing its basic nature.

Some general information on Belgian four-system receivers was provided in a Wireless World 1956 November article, see page 559 ff.  (Available at:  http://www.americanradiohistory.com/Wire...gazine.htm.)

And some Philips receiver circuits for study are available at:  https://frank.pocnet.net/instruments/Phi..._docs.html.  (Only some of the receivers on that list are of the Belgian four-system type.)

Cheers,

Steve

Belgium discontinued 819-line broadcasts in 1968 and, by the time I first visited Belgium in 1973, the French were in the process of closing down their 819-line system so I doubt there was any real continuing demand for the additional cost of providing 819-line reception just for one channel - the 2nd and 3rd French programmes were on 625-lines, anyway.

Nevertheless, it was interesting to see the sets on display in shop windows. Often two, visually identical sets would be shown side by side but at very different prices! The expensive one was obviously the multi-standard version.

Shortly after, cable TV reached the coast - it had started in the difficult reception areas of the Ardennes in the east and worked its way west across the country. The take-up was virtually instantaneous! One year every building on the coast (or so it seemed at the time) was bristling with massive aerial masts, often guyed to  all four corners of the building. Band I,III, IV & V arrays pointed in virtually every direction - there was no point is directing a VHF array towards Dover, for example - and some featured rotators.

A year later and they had virtually all disappeared. As a manager at Tevewest explained to me, it was easy to attract customers to cable as they could save considerably more than the annual subscription in the savings from buying a single standard TV. I would guess that the insurance on all those aerial installations didn't come cheap, either, as they all came down very quickly!

Compared to UK cable, the interesting thing is that Belgian cable didn't really offer its subscribers much more than they already had! Apart from one subscription channel - Filmnet - which required a decoder plugged into the SCART connector, every channel was free-to-air already!

A typical line up on the coast in pre-cable days was (starting from the north and moving clockwise):

NOS1 Dutch
NOS2 Dutch
BRT1 Flemish
BRT2 Flemish
RTBF1 Walloon/French
RTBF2 Walloon/French
TF1 French
A2  French
FR3 French
BBC1
BBC2
ITV (Southern)

To this line-up, cable added the following:

RTL Luxembourg/French
WDR German
ZDF German
RAI Uno Italian

There was also a Mozaic channel containing miniaturised versions of all these channels on a 4 x 4 matrix and the Filmnet channel.

Of note is that RAI was the only channel provided from a satellite feed! (There are large numbers of Italian immigrants in Belgium.)

Obviously, pre-cable the UK channels probably didn't travel far once you moved away from the coast and some of the others might be a bit problematic as you went further from the appropriate border but Flanders, in particular, is very flat!

The initial cable network only extended to 300MHz, so all programs used VHF channel which meant additional 'special' channels were added both above and below Band III and Set Top Converters were provided. However, manufacturers quickly developed multi-band tuner units and the converters were quickly phased out. Later, the Hyperband was added (300 - 470MHz) and tuners finally offered continuous tuning from 47 - 862MHz!

It is, perhaps, ironic that, within a year or two of the collapse of what must have been the world's largest market for multi-standard receivers, the likes of Philips were producing multi-standard PAL/SECAM/NTSC IC decoders for very little more than the cost of the single standard variants!