South African TV

[colly0410]

Largest screen for 405 we ever had was 19 inches & you could just see the lines, my auntie Kath had a 23 inches set & the lines drove me mad, I suppose spot wobble would have helped. In 1972/3 my parents bought a Sony 18 inches colour job (the one that converted PAL to NTSC) & got a 12 inches B/W Elizabethan portable free that I still have...

[ppppenguin]

Funny thing is that in the 405 to 625 transition period people often preferred the 405 line pictures. Some of this was likely due to poor performance of early dual standard sets on 625. Low contrast and/or noisy pictures were a common problem. Valve UHF tuners were not exactly high performance. There is also a psycho-optical effect, when you can see the line structure the picture can appear sharper. Even though it isn't.

[Mike Watterson]

Our first dual standard TV (I forget model but UHF was a vertical scale 21 - 68 tuned with a single knob at the bottom) was much better on 625 than 405. We used to marvel at the trade test short films. (Divis). I'm thinking it was maybe 21"?

[colly0410]

A mate of mine (featured on another now closed forum) believed that a modified system N with positive video & AM sound would have been the best 625 system for the UK, other posters disagreed though..

[ppppenguin]

There were various byways in the choice of TV systems. Our 405 and France's 819 were ultimately dead ends, though successful in their own way. Brian Pethers, who worked for the GPO, then BBC, then Michael Cox Electronics, proposed a SECAM-like system that was one of several discussed by Carnt and Townsend in Volume 2 of "Colour Television". See pp221-240.

System N was a nasty kludge for Argentina who had the unfortunate combination of 625/50 TV with 6MHz US style channels. It was only ever used for transmission, all production was done with standard PAL equipment. I was at Michael Cox Electronics when we won a contract to supply Argentina with PAL-B/G to PAL-N transcoders.

Strictly speaking PAL-B/G refers to RF transmission standards. In the studio it's simply PAL, with 4.43MHz subcarrier. The only other PAL variant that was used on air was PAL-M in Brazil. This was a properly engineered 525/60 version of PAL. Since it was a small market, all production was done in NTSC with transcoding to PAL-M for transmission.

Both these transcoding processes were fairly simple since field and line rates were the same for input and output. Incidentally SECAM was a horrendous system for production. You can only fade or mix it by partially dismantling it, a lossy process. I remember that Cox made native SECAM vision mixers which were both complex and horrible. It's no surprise that much French and Eastern European material was made in PAL, then transcoded to SECAM. It's also not surprising that France led the way in analogue component video for production. Meant that all routers, mixers and suchlike had 3x complexity but once Betacam component recorders were availabe it just worked brilliantly and gave a smooth upgrade path to digital production.

[Hartley118]

Funny thing is that in the 405 to 625 transition period people often preferred the 405 line pictures. Some of this was likely due to poor performance of early dual standard sets on 625. Low contrast and/or noisy pictures were a common problem. Valve UHF tuners were not exactly high performance. There is also a psycho-optical effect, when you can see the line structure the picture can appear sharper. Even though it isn't.

Odd thing this subjective crispness of 405 line pictures.  I recall it well - starting with the remarkable 12-inch Pye FV1 in 1951.  It's unfortunate and misleading that the only TV recordings we have from the 1950s are on fuzzy telefilm, giving the impression that pictures were then low definition.  They weren't! - they were sharp and crisp.

Progressing to 1964 on a 23-inch dual standard Murphy, the 405-line picture did have a visible line structure, but somehow had more punch than the 625-line BBC2 picture which lacked contrast and subjective sharpness.  Maybe those dual standard designs had been rushed into production too quickly?  They tended to be short of video gain.  And maybe there was a bit of ringing on the 405-line picture that contributed to the punch.

It was only in 1970 with a UHF-only Bush (with decent black level) that I felt we were at last seeing the full benefit of the 625-line picture.

Martin
  

[Mike Watterson]

Maybe some 625 dual standard sets just weren’t good.
In early 1970s had about 5 or 6 repaired 405 sets and a dual standard model soldered to 625.
I don't remember from mid 1960s to mid 1970s seeing ANY 405 set that looked better than a 625 model.

[Synchrodyne]

My expert says:

quite simply they wanted to be different* to encourage manufacture in SA. Completely misguided. The 42 to 68MHZ is  or was a military band at the time.

So System I was because of politics.

(* Because if you look at PAL I, EXCLUDING South Africa, hardly anyone used it compared to other PAL versions.)

I am inclined towards circumspection when it comes to accepting as “completely misguided” the South African decision to adopt System I.
 
The relatively small number of countries that used System I reflects the fact that it was a late entry, and that by the time it was available, the majority had already chosen their TV transmission system.  And of those yet to make a choice some were in the Francophone group for which System K’ had been developed.
 
Looked at another way, had South Africa chosen System B/G/H in the 1970s, that could well have been described as being retrograde.  By the late 1950s I think it was generally recognized that the Gerber compromise 7 MHz channel and 5 MHz vision bandwidth was too much of a compromise.  On that basis those major countries that had yet to introduce a 625/50 service, and could support the development and implementation of an improved transmission system were prudent to have done so.  In fact during the 1950s there were UK commentators were quite critical of the Gerber system, and some recommended a 7.4 MHz vision bandwidth, which was a bit unrealistic.  The 1949 UK industry export 625/50 system proposal was predicated on a 6 MHz vision bandwidth.
 
As I recall, manufacture of TV receivers in South Africa with significant local content was mandatory in the early years of TV there.  So there was no need for a technical non-tariff barrier to imports, given that they were prohibited anyway.
 
As to the visible performance of the different transmission systems, here is something I wrote for another forum a while back:
 
I have lived in both System B and System I countries – two of each - and also in a System M country, so I have had on-going exposure to three systems. The sequence was B, I, B, M, I, M, B, B. 

My overall impression was that System I pictures were generally a bit better than System B pictures.  The best way I can describe it is that System I pictures were somehow “cleaner” or “calmer”.  I shouldn’t say that they were obviously of wider bandwidth; rather that there was less distracting stuff going on in the background that shouldn’t have been going on.  That was the impression that I had when I first saw System I pictures, and it didn’t change over many years.  Given that this came from watching a variety of receivers, mostly of the domestic type, and probably few of which took full advantage of the transmitted bandwidth, I’d say that the difference had less to do with the primary effects of receiver vision bandwidth choice, but more with the secondary effects of the bandpass filtering and any baseband peaking, such as phase-shifting, ringing and so on.  Perhaps that kind of picture deterioration should have been reduced as compared with the early days once synchronous demodulation and SAW filters became established, but then the greater part of the above observation period was in the synchronous/SAWF era. 

I should note that System M was no cleaner than System B, and I’d say that, at least as seen on conventional 25-26 inch screen CRT receivers, the vertical definition was only just enough.  But System M had a big advantage in terms of freedom from flicker.  Once you were accustomed to it, then the flicker with 50 Hz pictures encountered when travelling was very noticeable.  After a move from an M area to a 50 Hz area, it was quite a few weeks before one adjusted to the flicker and no longer noticed it so much. I also noticed the difference between B and I when on trips that took in both Singapore (B) and Hong Kong (I), that despite the vagaries of hotel TV systems. 

I have had only passing acquaintance with Systems D/K and L.  But I do remember looking at D/K pictures in a domestic setting in Lanzhou, China back in 1987 and thinking that they were as “clean” as System I pictures.  The same with System L; I recall looking very closely at a B&O receiver in Paris in 1996, in particular to see if I could find any obvious signs that it was a positive modulation transmission, but no luck on that. 

The foregoing is simply one layperson’s observations and perceptions, essentially subjective and mostly with sequential rather than side-by-side comparisons. Naturally it embodies any biases I may have, and perhaps an element of self-suggestion.
 

Cheers, 

Steve

[Mike Watterson]

My expert says:

quite simply they wanted to be different* to encourage manufacture in SA. Completely misguided. The 42 to 68MHZ is  or was a military band at the time.

So System I was because of politics.

(* Because if you look at PAL I, EXCLUDING South Africa, hardly anyone used it compared to other PAL versions.)

I am inclined towards circumspection when it comes to accepting as “completely misguided” the South African decision to adopt System I.

No, he wasn't saying the adoption was misguided. He's a Telecom guru, he has no opinion on that aspect. He meant that their idea of picking a "less popular" PAL would lead to SA local TV makers supplying most of TVs was misguided. It didn't happen!

Many later analogue sets had actually 5.5MHz and 6.0MHz ceramic filters so that the same set could be supplied to mainland Europe or Ireland (the UK models often were "cost reduced" and had UHF only tuners. By early 1990s most sets in Ireland did I and B/G via Aerial and NTSC via baseband. I'm not sure if the SECAM was supported via RF, but certainly French SECAM for TX sites via satellite worked via composite.

Like SCART/Peritel, the idea of  picking System I for indigenous manufacturing protection was a failure. The Government was was going to do a deal at Digital (with Brazil?) for a least used Digital Standard for same reason, but unlike System I (which had no particular technical downside), the Digital solution was crazy compared to DVB-T, so SABC, the Tech Industry, TV sellers etc all rebelled and the Government did a U turn on that stupidity.

[colly0410]

Been thinking: If South Africa had started their TV broadcasts a few years later when synchronous demodulation & SAW filters became more widespread if they'd have gone for system D/K, as there would then have been no real advantage for a 1.5 Mhz vestigial sideband as used in system I. AFAIK the wider vestigial sideband is only an advantage with older style diode detectors. Just my 2 pence worth...