Philips 819 line TV receiver.

[Geordie McBoyne]

Not having a good time with the set today. The tuner unit has developed a fault. The tuner was found to be set to channel F5 and in an attempt to secure better definition the tuner was reset to the F8/F8A position. Now one of the oscillator coil contacts doesn't connect with the biscuit studs. The tuner was taken out, the turret drum removed and the contacts cleaned. After reassembly and testing the tuner still doean't work, so tomorrow it's out with the tuner again.
The Philips turret tuner is similar to the unit fitted in the UK manufactured models 1768U and 1796U. Valves are PCC84 and PCF80.
Fortunately for me the set is very easy to service. It's just a matter of removing two screws, unplug the scanning coils and loudspeaker, take off the CRT base and EHT connector and slide out the chassis leaving the CRT in position.

Geordie McBoyne.

[Terry]

You said this set had reduced bandwidth, as did many 819 sets.

Don't forget that Belgium used a version of the 819-line system but crammed into a standard 7MHz channel with a 5MHz vision bandwidth. It would have been a simple matter to make receivers with a 5MHz vision bandwidth and switchable sound frequencies so that French viewers living within reach of the French language transmitters in Wallonia could have a choice of viewing. The same sets could also have been sold in Wallonia to give the Wallooons the same choice, in reverse, of RTBF and RTF.

[Geordie McBoyne]

Terry wrote:

"Don't forget that Belgium used a version of the 819-line system but crammed into a standard 7MHz channel with a 5MHz vision bandwidth."

Apart from having the advantage of the fine line structure, the horizontal definition must have been poor.
Remember that the VHS video bandwidth is only 3Mhz and the pictures always look "soft".
From the UKVRR: a discussion about transmitting a 625 line TV in a System A 5Mhz channel.
The consensus was that the 405 line picture looked better than the narrow bandwidth 625.
https://www.vintage-radio.net/forum/show...p?t=123614&highlight=narrowband+625+line+TV&page=2

Geordie McBoyne.

[ppppenguin]

Syetem N (as used in Argentina) did put a 625 picture in a narrow channel. 6MHz rather than 5 but still not really enough. A consequence of US channel planning with 50Hz mains. Then they added colour.

[Synchrodyne]

Belgian TV receivers were four-system from the start in 1953, covering Systems B, C, E and F.  The reason for System F with its overly narrow vision bandwidth was that all Belgian transmitters had to be able to broadcast either 625- or 819-line signals according to the incoming programme format, although 625 and 819 were nominally standard for Flanders and Wallonia respectively.  For more detail, see Wireless World (WW) 1956 November pp. 559 through 562, “Four-Standards Television”.  With the advent of UHF, five-system receivers were introduced, covering Systems B/G/H, C, E, F and L.

Typically, the Belgian multi-system receivers covered only a handful of Band III channels for System E, logically only those that were receivable within Belgium.  Given that they used a vision-high IF, then including the Band I channels F2 and F4 in the tuning range would have been awkward to say the least.  Channel F3 would have been possible, but although nominally allocated at ITU Stockholm 1952, that channel was rendered unusable by the French decision to standardize on a vision-low IF, in place of previously-used double-ended IF strips.

French border-area multi-system TV receivers appear to have started out with the so-called Strasbourg models in the mid-1950s, but as best I can determine design generally coalesced around the Belgian approach.  But there were one or two that also covered System A, so those must have had IF arrangements that also accommodated inverted Band I channels.  I suspect too that the French makers of multi-system receivers may have made more effort to obtain reasonable visions bandwidths (at least well above 5 MHz, say around 7 MHz or so) on their own System E.  The Belgian makers may have seen less need to have the System E pictures any better than those of System F.

The Argentinean System N appears to have had its origins in the experimental American-origin 625-line transmitter installed at Torino, Italy in 1949.  This operated in channel A6 (82 to 88 MHz) and basically followed the NTSC standard except that it was 625/50 instead of 525/60.  So that set a precedent for Argentina, whose regular TV service started in 1951, ahead of that of most Western European countries.  Evidently adhering to the same American channel allocation pattern throughout South America was considered to be of overarching importance.

At the time, the prevailing thought, derived from the 1941 NTSC deliberations, was that there was quite a bit of flexibility in the relativity between vertical and horizontal definitions, and that it was paramount to have a line count that was sufficiently high to avoid undue “lininess” and to provide adequate flatness of the field.  Thus Donald Fink moved the NTSC thinking from 441 to 525 lines.  The NTSC 6 MHz channel was evidently seen as attractive by some in Europe, but by others seen as not enough for 625 lines.  The Philips 567-line proposal was an effort to provide an optimum line count for a 6 MHz channel with 4 MHz vision bandwidth.  However reasonable it might have been, it was surely doomed as a lower line count than the 625 already used by the Russians was hardly likely to fly.  As best I can determine the debate within the CCIR Gerber sub-committee was between a 6 MHz channel with 4.25 MHz vision bandwidth and a 7 MHz channel with 5 MHz bandwidth.  The Russian 8 MHz channel with 6 MHz vision bandwidth seems to have been dismissed as probably “too expensive” in bandwidth terms and perhaps for political reasons as well.  That the apparent lower option studied by Gerber was 4.25 MHz was interesting, given that NTSC was then 4 MHz.  One may deduce that its proponents saw that 4 MHz was a “bit thin”, so as to speak, and wanted to push out to a barely possible limit.  NTSC moved out to 4.2 MHz with the advent of colour in 1953.  The Gerber decision seems to have been somewhat of the “political” art-of-the-possible kind, as the 7 MHz channel was really on the short side.  

System N was also one of the contenders for Japan, where NTSC won the day.  Italy adopted the 7 MHz channel, but the legacy of that experimental transmitter was that its channel frequency was more-or-less retained, adjusted to 81 to 88 MHz, as Italian channel C.  Early on Italy also followed American practice by adopting a standard IF channel of 40 to 47 MHz with 45.75 MHz vision carrier (the American “high” IF channel was 41 to 47 MHz with 45.75 MHz vision carrier), and this meant that it could not use the lower end of Band I.  I suspect that interference possibilities stemming from this choice of IF led to the non-standard spacings of its Band III channels.

As far as I know, System N retained the NTSC “6-pack” equalizing pulse structure until the end.  System B started that way, but moved over to the “5-pack” in the early-to-mid 1950s.  System D probably followed a bit later, but System C was “5-pack” from the start.

System N also had the NTSC FM sound parameters of ±25 kHz deviation and 75 µs pre-emphasis.  These were the 1945 NTSC numbers; the original 1941 version having been ±75 kHz and 100 µs.  The ±50 kHz and 50 µs numbers used in Europe might have come from the original Russian 625-line work.  Certainly Russia used the same numbers for its Band I FM sound broadcasting (and for which combination the Zenith-GE stereo system apparently did not work well enough, hence the development of the alternative polar modulation system).  Early FM broadcasting work by the BBC circa 1944-45 showed that 50 µs was better than 100 µs (with later work showing that 50 µs was still better than 75 µs) so that also might have been the origin of the 50 µs pre-emphasis number.        

The UK TAC realized that the Gerber standard was a bit short on vision bandwidth, and was originally thinking in terms of the Russian 8 MHz channel with 6 MHz vision bandwidth.  But the Russians appeared to have overlooked the desirability of proportionality between the main and vestigial sidebands, simply taking the established NTSC VSB number of 0.75 MHz and using it with a 50% wider main sideband.  On the other hand, the French opted for a 2.0 MHz VSB to match their 10.4 MHz main sideband in the 819-line system.  So the TAC opted for a 1.25 MHz VSB with a 5.5 MHz main vision sideband within an 8 MHz channel.  The French combined the 1.25 MHz VSB with a 6.0 MHz main sideband for Systems L and K’, by dispensing with the outer guard bands, which is what they had done previously when the definitive tête-bêche channelling for the 819-line system adopted 13.15 MHz channel spacing in place of the original 14 MHz.

Interestingly, Donald Fink, in one of his later writings, suggested that 8 MHz would have been the optimum analogue TV transmission channel width.  But the American 6 MHz was one of the fixed parameters handed to the first NTSC, so was not up for reconsideration.


Cheers,

[Terry]

Belgian TV receivers were four-system from the start in 1953, covering Systems B, C, E and F.  ... With the advent of UHF, five-system receivers were introduced, covering Systems B/G/H, C, E, F and L.

Belgium discontinued use of System F in February 1968 and France, after attempting an 819-line version of SECAM, dropped it in favour of 625-lines and started switching their TF1 service from System E to System L. System C also fell by the wayside - probably after System F disappeared - and both services were then carried using System B.

However, after the UK started transmitting all three services on UHF in 625-line PAL in late 1969, System I was added to the mix.

Anybody visiting Belgium, particularly Flanders in those days cannot have failed to notice the vast aerial arrays on virtually every roof. These were usually guyed to all four corners of the roof and, I would imagine, cost a fair bit in insurance. On the coast, for example, they would point inland for the local BRT chanels, South for the RTBF channels and TF1, A2 and FR3 from France, North-east for NOS1 and NOS2 from the Nerherlands and slightly south of east to the Dover IBA transmitter for BBC1, BBC2 and ITV! Most, bar the UK channels, needed a mix of VHF and UHF arrays, of course. In the windows of TV dealers there would often be two sets side by side, aparently identical, but with entirely different price tags. The cheap one would be a normal System B, G,H receiver whilst the one with the much higher price would be the multi-standard one!

Then, in the mid 70s, as if by magic, they all disappeared!

Cable TV had arrived! Those magnificent arrays were no longer needed, nor multi-standard sets, as all signals were converted, if necessary, to PAL System B at the headend.

As a senior technical manager at TV-West, the operator on the coast, explained to me a few years later, "For us it was easy. We could say that if you take our service, it will cost you considerably less in a year than you will save when you buy a new TV!"

The take-up was even more surprising because, unlike here, where lots of satellite and other programming have always been part of the cable package, litte more was provided in Belgium than the subscribers could receive themselves without the cable!

The only satelite channel was RAI Uno (there are a lot of Italian migrants in Belgium). Also added to the previous mix were RTLi and WDR and one subscription channel - Filmnet - which was scrambled and required an external decoder plugged into the SCART connector..

UK TV was now available to all subscribers rather than just those living near the coast.

So, that first channel line up was: BRT1, BRT2, RTBF1, Télé 21, NOS1, NOS2, TF1, A2, FR3, RTLi, WDR, BBC1, BBC2, ITV, RAI Uno and Filmnet.

There was also a Mosaic Channel so all of these neatly fitted into a 4 x 4 mosaic!

Intially, subscribers were issued with set-top boxes for channel selection. They received the incoming cable signal - continous coverage from 47-290MHz - and converted the selected programme to a channel in the broadcast bands.

These didn't last long, though. The high takeup was sufficient to ensure that new continous coverage tuners were developed and fitted to all new TV sets sold in Belgium within a couple of years!

In later years, as Amplifiers appeared, capable of wider bandwidths whilst retaining the ability to conform to the strict noise and distortion specifications required, the 290MHz limit was abandoned, the 300 -470MHz band became 8MHz TV channels and some European cable networks are now capable of operation over the entire 47-862MHz bandwidth.

[Synchrodyne]

As far as I know, System C lasted until 1978.  I’d guess that System F was abandoned once standards conversion equipment that was reliable enough, economic enough and had an output of sufficient quality for full-time use was readily available.  Given that all of the Belgian transmitters were from the start designed to handle both Systems C and F, then at the transmission level the abandonment of System F would have been painless.

The original French SECAM work, with 819 lines and an 8.37 MHz AM subcarrier was described in Wireless World 1957 September, pp.426 to 429.  I imagine that very soon after, it would have been apparent that the second French TV service, in the UHF band, was going to use 625 lines, hence development work was switched to that standard.  Whether the change from an AM to a FM SECAM subcarrier occurred before or after the line-count change I do not know.  Conceivably the French chose a 6 MHz vision bandwidth for the 625-line service to avoid undue truncation of the SECAM upper colour FM subcarrier sideband.  Vestigial sideband FM might have been seen as being a bit awkward.  (The only example of asymmetric sideband FM that I am aware of is in the CD-4 four-channel gramophone disc system, herein the subcarrier is single sideband FM for audio frequencies above 10 kHz.  Any resultant harmonic distortion would have been above the audible band.)

When System L was extended to Band I, after the closure of System E, it required inverted channels and was known as System L’.  Standardization decisions sometimes have a very long reach and perhaps unintended consequences.  In the mid-1950s, the System E receiver IF was standardized at 28.05 MHz vision, 39.2 MHz sound.  Since oscillator low was not possible at Band I, this eliminated channel F3 but allowed the use of channels F2 an F4, both inverted.  So at the time it would have been a better choice than the alternative 35.7 MHz vision, 24.55 MHz sound, which would have eliminated channels F2 and F4.  With System L, the chosen IFs were 32.7 MHz vision, 39.2 MHz sound, the latter being common with System E for ease of dual-standard receiver design.  This was fine with the 625-line channels at UHF and Band III, where oscillator-low operation was possible.  But it required inverted channels for Band I in order to fit oscillator-high operation, no problem for regular domestic receivers but awkward for multistandard receivers.


Cheers,

Steve