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Old 5th Mar 2011, 7:14 pm   #81
Maarten
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Default Re: 240, 405 & 625

I agree on that last sentence

As a continental European however, I should add that we once had those different measuring systems as well. The Inch, foot and yard were almost universally used across Europe. So were the pound and ounce. In the Netherlands, the metric pound and ounce (500gr, 100gr) are still in use. At the same point in time those were introduced, someone saw it fit to redefine the inch (duim or thumb as it was called here) to 1cm. However everyone called it a centimeter so by now a duim is 2,54cm again, but seldomly used.
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Old 6th Mar 2011, 12:54 am   #82
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Default Re: 240, 405 & 625

Hi Maarten,
I understand that in Holland an experimental 567 line system was tested after WW2. A development of the 405 line system?

405 = 9X9X5. 567 = 9X9X7.

DFWB.
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Old 6th Mar 2011, 3:31 am   #83
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Originally Posted by BGmidsUK View Post
This is worth considering .. had we gone along the 625 route, what impact would that have had on the launch of the ITA service? I very much doubt BBC national coverage could have been achieved (mostly) with Band I alone, meaning Band III would have been used more. This would very likely have forced us onto UHF before the technology was ready (in fact it probably wasn't even when BBC2 was launched!) - or significantly held us back. What commercial impact could that have had on our recovering economy? I'd be interested to know when the Continentals started launching additional channels, and what bands were used.
In fact the original BBC plan was to use the five Band I channels and a couple of Band III channels to obtain national coverage. This situation obtained until at least the initial TAC report in 1953; see Wireless World for August 1953. Secondary transmitters originally planned to use Band III included Norwich, Cumberland, Londonderry and West Wales amongst others. The BBC was forced to recast its plan to obtain national coverage using only the five Band I channels. That it could obtain national coverage using only Band I was a consequence of the narrow 5 MHz channel required for 405 lines, combined with carefully controlled power outputs and directivities for the secondary transmitters. (The effects of this close-to-overpacking of Band I can be seen by overlaying the BBC Band I and Band II FM networks. In the latter case, the greater number of channels plus to some extent the slightly shorter propagation distances allowed higher powers for the secondary transmitters relative to the main transmitters and in many cases they could be omnidirectional.) However, given the original BBC plan, the obtaining of national coverage using Band I only may be seen as an incidental benefit from choosing 405 lines, but could not have been a reason for it in the late 1940s. Also referring to Wireless World for August 1953, by then BBC had developed two-program a national coverage plan using both Bands I and III.

Arjoll has also quoted the New Zealand case, which shows that there would have been enough channel space in the two bands to obtain two program national coverage using 7 MHz 625-line channels.

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Might not be relevant, but New Zealand had three VHF networks pretty much nationwide and a fourth VHF network in main centres, and NZ has used system B from the beginning, PAL since the mid 70's and NICAM since 1989.

There are some small pockets of UHF infill on TV3 in areas like Queenstown (because of terrain there are about 4 or so translators there so VHF was a bit chokka with TV1 and TV2) but for analogue we are predominantly VHF - in fact until the late 80's it was rare to see a TV with a UHF tuner, and UHF aerials were rare in the cities until Sky came along (UHF with Videocrypt, now switched off).
New Zealand is comparable in size to the UK, and is topographically more difficult. My recollection is that the original plan was for two program national coverage using the 9 VHF channels, 3 in Band I and 6 in Band III. Whilst TV1 had the lion’s share of the Band I allocations (7 out of 8 main transmitters, I think), at least two main sites had both TV1 and TV2 in Band I.

So one might reasonably conclude that had the UK chosen 625 lines been chosen in the late 1940s, the advent of ITV in 1955 would not have required the use of UHF channels in order to obtain national coverage. The BBC would probably have started using Band III channels around 1952, say when the Wenvoe (Cardiff) transmitter came on line, by which time the pertinent receiving technology was well-developed.

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Originally Posted by BGmidsUK View Post
Remember the US channel allocation is much narrower than that used in Europe (and needed for decent quality 625-line transmissions) with resultant lack of definition on their 525-line system - this is how they managed to squeeze more services into the existing bands!
6 MHz channels for the NTSC 525-line system vs. 7 MHz for the CCIR 625-line system, although the USSR chose 8 MHz channels. The resultant wider IF bandwidth required for 625 lines was probably the only point of difference that made 625-line receiver design a tad more difficult than that for 525 lines. Otherwise the receiver technology developments driven by the growth of TV in the USA easily read-across to the 625-line case, with minimal innovation required. For example, the line frequencies were very similar. Interestingly, the choice of 525 lines for NTSC was driven by the optimum that could be fitted into a 6 MHz channel, the latter parameter having been chosen first.

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Originally Posted by Duke_Nukem View Post
Choosing a higher bandwidth system would mean either reducing the number of channels – and how they managed to cover the whole uk with just 5 channels is an achievement – or using higher frequencies at a time when the trusty EF50 was all we had.
See my earlier comment in respect of the original BBC plan to use Bands I and III. That the US was using all of its VHF channels ensured that adequate Band III receiving technology would be available when required in the UK. But were a better EF50 thought to be the solution, then it did actually exist circa 1946 in the form of the 6AK5 (EF95). However, the real answer to good and stable RF amplification at around 200 MHz lay with the cascode double triode, developed in the US and available, I think, around 1950, coupled with the turret tuner.

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Originally Posted by peter_scott View Post
The war was a boon to radio manufacturers but peace time could easily have brought years of low sales and lack of funds for further development. CCIR SG XI didn't standardise the 625 line system until July 1950 and to jump to some yet to be agreed standard during the previous 5 years would have been plain silly.
I am not sure of the exact chronology of the 625-line system but I think it was developed in Germany in the immediate post-WWII years as more-or-less a 50 Hz analogue of the NTSC system. CCIR took quite a long time to standardize it in 7 MHz channel form, whereas the USSR adopted it in 1948 (I think) with 8 MHz channeling. I have never seen the reasons for the difference in channel band width choice, nor what was proposed by the original developers. But given its origins as an NTSC derivative, the major parameters were probably reasonably easily derived, and CCIR’s late standardization effort would not have been a serious impediment to its adoption in the UK (or elsewhere) in the late 1940s. Certainly, and whether with 7 or 8 MHz channeling, it would have been well-enough defined by the time the BBC’s first regional transmitter (Sutton Coldfield/Birmingham) came on line in 1949. Now there’s a thought. The London service could have been restarted on 405 lines, but the regional expansion could have been on 625 lines, although there would no doubt have been many difficulties with that idea. London on channel B1, Sutton Coldfield on E4, Holme Moss on E2, Kirk O’Shotts on E3, then perhaps Wenvoe the first to use a Band III channel. Also, even had the BBC stayed with 405 lines, ITV could have been 625 lines in Band III from the start, and perhaps to ease the design of dual-standard receivers, the Belgian 625 line variant (positive vision modulation, AM sound) could have been used.

Overall it seems to be difficult to find cogent technical/technology reasons that support the 1940s decision to retain 405 lines, or that at least point to major difficulties to achieving success with higher standards. At the time, I suspect that it was realized that something better would be needed in the future, but it may not have been clear just what that would be, and for example the adoption by France of the 819 line system could have clouded the issue somewhat, making 625 lines not an obvious good bet for the future. That 625 lines turned out to be the “Goldilocks” system, as noted by Jeffrey (ppppenguin) could not have been known at the time. But by 1954-55 it was surely apparent, so perhaps the criticism, such as may be justified, should be aimed more at those in authority who failed to “bite the bullet” at that time and start ITV on 625 lines. I don’t think that by then it could have reasonably been claimed then that future uncertainty pointed to retention of the status quo; it looked more like a case of postponing the tough decision for expediency reasons. Having ITV on 625 lines with BBC on 405 lines may have been seen as giving the new service a technical edge, but then the 405-line proponents have argued that it was adequate for the time and/or that the realizable differences were but minor, so would that have been a material issue?

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Old 6th Mar 2011, 7:37 am   #84
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Originally Posted by Synchrodyne View Post
My recollection is that the original plan was for two program national coverage using the 9 VHF channels, 3 in Band I and 6 in Band III.
That sounds about right. I'm not sure when channels 10 and 11 came along - I know that Dunedin had TV3 on channel 10 in 1989 (moving to channel 9 when TV4/C4/FOUR started on channel 11). My parents have a late 70's Thorn 12" B&W portable with channels 1-9, and I have a 1984ish NEC 13" colour which goes up to channel 10, so I suspect 10 and 11 were squeezed in quite late in the piece.

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Originally Posted by Synchrodyne View Post
Whilst TV1 had the lion’s share of the Band I allocations (7 out of 8 main transmitters, I think), at least two main sites had both TV1 and TV2 in Band I.
Hedgehope (our local) and Te Aroha? I know that here a band I/III aerial was called a "TV3 Aerial" for quite a few years when people started having ch 1-3/6-8 aerials to replace the old band I (some still just ch 1) 3 element yagi which were common before. Those of course are now replaced by 1-3/4-11 aerials to pick up CUE (ch 5) and FOUR (ch 11)!
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Old 6th Mar 2011, 8:45 am   #85
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Quote:
Originally Posted by arjoll View Post
Quote:
Originally Posted by Synchrodyne View Post
My recollection is that the original plan was for two program national coverage using the 9 VHF channels, 3 in Band I and 6 in Band III.
That sounds about right. I'm not sure when channels 10 and 11 came along - I know that Dunedin had TV3 on channel 10 in 1989 (moving to channel 9 when TV4/C4/FOUR started on channel 11). My parents have a late 70's Thorn 12" B&W portable with channels 1-9, and I have a 1984ish NEC 13" colour which goes up to channel 10, so I suspect 10 and 11 were squeezed in quite late in the piece.
.
Yes, I think that Channels 10 and 11 were freed up quite late on. Neither was in use when I left NZ in 1985.

Quote:
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Quote:
Originally Posted by Synchrodyne View Post
Whilst TV1 had the lion’s share of the Band I allocations (7 out of 8 main transmitters, I think), at least two main sites had both TV1 and TV2 in Band I.
Hedgehope (our local) and Te Aroha? I know that here a band I/III aerial was called a "TV3 Aerial" for quite a few years when people started having ch 1-3/6-8 aerials to replace the old band I (some still just ch 1) 3 element yagi which were common before. Those of course are now replaced by 1-3/4-11 aerials to pick up CUE (ch 5) and FOUR (ch 11)!
Yes, Hedgehope and Te Aroha. By virtue of using channels NZ1 and NZ3, and its height, Te Aroha had a huge footprint. TV3 in Tauranga was on a high Band III channel from a different transmitter to the east, so clearly the TV3 shoehorn job meant abandonment of co-siting in some cases. My parents’ retirement house in Tauranga had a separate TV3 aerial, pretty much opposite-pointing to the Te Aroha aerial, coupled in with a diplexer. I imagine that those Te Aroha Band I aerials vertically polarized and typically 3-element, would have looked familiar to our UK readers. Channel NZ1 was nearly as low as B1 in frequency, hence big aerial elements were required. Originally in NZ though, 300R ribbon cable was used, with the change to 75R coax arriving more-or-less with colour. Typically aerials were coupled to the coax via baluns, rather than directly as seemed to have been common in the UK.

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Old 6th Mar 2011, 9:55 am   #86
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Quote:
Originally Posted by Synchrodyne View Post
Having ITV on 625 lines with BBC on 405 lines may have been seen as giving the new service a technical edge, but then the 405-line proponents have argued that it was adequate for the time and/or that the realizable differences were but minor, so would that have been a material issue?
Accepting the decision to go with 405 in 1946 and questioning the decision to use 405 for the start of ITV is an interesting scenario to ponder.

My initial thoughts on reading Synchrodyne's suggestion were not so much that ITV would appear to be technically superior but rather the reverse. Much has been written in this forum about the horrible grey images when BBC2 started up and I well remember this and the poor noise performance of the early UHF front ends.

Whilst the initially poor technical qualities of 625 transmission may not have been known to policy makers in 1955 it will certainly have been apparent to ITV promoters that they would gain nothing from the installed base of television sets if they had opted for that route.

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Old 6th Mar 2011, 10:33 am   #87
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But I don't think that the "grey pictures" phenomenon was inherent with 625 lines. Rather that was simply the result of poor implementation. Certainly I don't recall anything grey about the New Zealand 625 line TV pictures. But then NZ monochrome valve receivers of the 1960s probably owed more to European and perhaps North American techniques than to British techniques. Thus it was normal for IF strips to have 3 frame grid stages (e.g. 1 x EF183 and 2 x EF184), as it was to have line and/or noise-gated black level agc, and fully isolated power supplies. Often the RF agc takeover point control was reasonably accessible, as well. Although this NZ expereince was at VHF, not UHF, during the early years good fringe area reception was a key factor, hence adequate gain and good agc. The main centre transmitters were not increased from 10 kW to 100 kW erp until around 1964, so signal strengths tended to be low even fairly close-in during the early days.

In fact the most common picture fault, or really picture fault setting that one saw was the "soot and whitewash" effect caused by black level being too low (brightness set too high) and the white level being set too high (contrast set too high). Typically regulation wasn't as good as it could have been, so that there was some black level droop as the contrast was wound up.

Thus the poor impression of 625 lines performance in the UK was evidently caused by poor receiver design, such as the use of mean level agc and possibly inadequate overall gain. UHF didn't help, but with adequate gain and good black level agc amongst others, lower signal strength should have resulted in noisier but not greyer pictures. The techniques required to do better were readily available from the worldwide 625-line exprience, and by 1962 UHF reception was hardly new. It seems that by and large the UK industry ignored the worldwide experience.

By the way, in sugesting that ITV might have started on 625 lines, I was assuming that the setmakers - or some of them anyway - would have done a better job in 1955 than they did with the coming of BBC2.

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Old 6th Mar 2011, 10:38 am   #88
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By virtue of using channels NZ1 and NZ3, and its height, Te Aroha had a huge footprint.
I know FM off there has exceptional coverage - RBG have Life fm serving two markets. I don't know the geography of the Waikato that well though (actually I'm a bit rusty on big chunks of the North Island).

I understand that Mid Dome was looked over for Southland for similar reasons - it would have caused too many problems with channel coordination in other areas. When our local trust engineered 100.0 up there for Life fm they had to consider possible interference to the same channel in Oamaru!

Quote:
Originally Posted by Synchrodyne View Post
TV3 in Tauranga was on a high Band III channel from a different transmitter to the east, so clearly the TV3 shoehorn job meant abandonment of co-siting in some cases.
Similar in South Canterbury, TV3 was sited on Cave Hill not Mt Studholme, which meant some relations in Fairlie had to have two aerials.

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I imagine that those Te Aroha Band I aerials vertically polarized and typically 3-element, would have looked familiar to our UK readers.
Was Te Aroha vertical as well? I assumed most of the main ones were horizontal! We are horizontal, as is Wellington which causes us lots of problems when there are skip conditions. Until TV3 came along my parents had a perfectly good signal on both TV1 and TV2 using a channel 1 aerial with the director cut down a little in length.

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Originally in NZ though, 300R ribbon cable was used, with the change to 75R coax arriving more-or-less with colour.
My parents were ribbon until the early 90's - I even did an install at our flat in Dunedin using ribbon because it was cheaper! I upgraded my parents place to coax around 1991 I think. Ribbon directly onto the folded dipole, balun at the back of the TV, then switching to one of those horrible 'easy fit' baluns at the aerial when coax was installed.
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Old 6th Mar 2011, 11:10 am   #89
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[Was Te Aroha vertical as well? I assumed most of the main ones were horizontal! We are horizontal, as is Wellington which causes us lots of problems when there are skip conditions.
Yes, of the North Island main provincial sites, both Te Aroha (Waikato/Bay of Plenty) and Wharite (Manawatu) were vertical. I think that Mt. Erin (Hawkes Bay) was horizontal, but I am not 100% sure. Auckland, like Wellington, was horizontal.

In my youth I had the good fortune to spend the best part of a day at the Waiatarua (Auckland) transmitter site in 1964 when the upgraded 100 kW erp installation was under way. The Marconi-EMI senders were being installed in the new hall, along with Marconi quadrant radiators on the new 400 ft tower being built by Italian riggers. Meanwhile transmissions were maintained by the existing 10 kW erp installation using the old 90 ft tower that looked very much like a converted electricity transmission tower. Te Aroha was a relay, then still 1 kW erp I think, and monitored at Waiatarua using a 4 or 5 element Yagi and a standard domestic receiver, side-by-side with a similar receiver with a direct fed from the adjacent Auckland transmitter. Whilst some interference was visible on the Te Aroha picture, there was certainly no greying. At the time I was surprised that such good reception could be had at the distance; even though both sites were elevated, more so for Te Aroha, there was high country (Hunua) in between.

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Old 6th Mar 2011, 3:29 pm   #90
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I think commercially if you'd started ITV on 625 lines it would have been difficult to get companies to invest. They needed to get an audience quickly, this was possible with bolt-on tuners for old sets but would have been difficult if new expensive sets had been required. Remember who the target viewers of the commercial services were - i.e. working and lower-middle-class households.

Also, bear in mind that most people really don't give a monkeys about quality so long as something is "new"...the number of times I've had somebody proudly pointing out picture faults as details on new TV makes me want to weep!

I have to say after all this I really can't see what better plan the government could have come up with, in the end prevarication was probably the correct course. After the war if I'd owned a pre-war TV and they restarted on a different format I'd have been mightily peeved - especially as I'd probably have been able to make a few bob out of the valves during the shortages. Also the BBC could more or less just start up - a big morale boost. Mucking around rebuilding transmitters, studios etc during a time of great privation would have been a slow, unpopular move likely to cause futher resentment.

The move to 625 was not at all obvious at the time and the choice of a colour system not at all clear even after the fact...No wonder the BBC and ITV companies were pushing for 405/NTSC which must have seemed a no-brainer at the time.

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Old 6th Mar 2011, 4:39 pm   #91
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Personally, I do not think there was any reason to think that "class" had anything to do with ITV. The BBC very much needed competition to improve its programming to be acceptable to a wide section of the public. The BBC sat very much on it's laurels up to the start of ITV, look at the success of Coronation Street from it's start in 1960, it's even a favourite with the Royal Family, everyone else is "lower Class" in comparison to HM's family!
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Old 6th Mar 2011, 9:11 pm   #92
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Well it did when in terms of advertising - in the 1950's the workers had the buying power. When you're selling soap powder, toothpaste etc numbers matter, nothing else, and that is probably what saved 405 lines for so long - it was the way to roll out more telly to more people.

This is easy to forget sometimes these days when the class system is a different kettle of fish but ITV had to appeal to as wide an audience as possible. When BBC2 came out on 625 lines it was definitely the very opposite in terms of the target demographic!

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Old 6th Mar 2011, 9:27 pm   #93
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Very true.
The BBC though up to the start of ITV were stagnating and catered for a highbrow audience, they of course did this with BBC2 and the early take up of BBC2 was poor, so was this the program content that caused lack of interest or the cost of buying dual standard TV sets or even the lower than expected picture quality.

When it comes down to class structure I shudder at it. My dad although a Aeronautical Design Draughtsman and clever was working class, my mother though was born to a high class family with her Dad having business's, loads of medals and an MBE, so we were brought up to treat everyone as equal. Sorry for being OT.
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Old 6th Mar 2011, 11:21 pm   #94
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Yes, using "class" in these contexts is quite difficult - and a very blunt tool - I've no idea where I fit in either! My point would probably be better made by saying lower income households.

Whatever the BBC were doing, switching to 625 lines for ITV would have been commercially unnatractive if most people could not or could not afford to receive it. It would then be an uphill struggle to coax people into buying new sets.

However it does still interest me how many receivers are found from the early 50's that seem never to have been upgraded for ITV.

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Old 7th Mar 2011, 9:29 am   #95
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The ITV converters were fitted across the board, with people from all walks in life wanting ITV, a good number would have the manufacturers tuners fitted too.
The cost would have been a converter, or a mod plus a band 3 aerial and either a new cable run or a diplexer, Quite expensive in the mid 50's but perhaps cheaper than a new set.
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Old 20th Mar 2011, 8:08 am   #96
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I think commercially if you'd started ITV on 625 lines it would have been difficult to get companies to invest. They needed to get an audience quickly, this was possible with bolt-on tuners for old sets but would have been difficult if new expensive sets had been required. Remember who the target viewers of the commercial services were - i.e. working and lower-middle-class households.
I can imagine that some in the ITV world would have been protagonists for being able to access the installed receiver base, although others would have been looking ahead to a massive growth in receiver count, seeing more return in persuading non-viewers to buy receivers than existing viewers to choose ITV over BBC. Given that an ITV franchise was seen as “a license to print money”, I doubt that commercial success was so delicately balanced that that accessing the installed receiver base was absolutely critical. I wonder though, what the receiver number statistics actually were in that period. How many Band I-only receivers were in use just before 13-channel receivers came on to the market late in 1954? How many of these were retrofitted with Band III adaptors? How many new receivers were purchased in say the first four years or so of ITV? How many of these went to first-time buyers and how many to existing users who decided to buy a new model (larger screen, etc.) rather than to retrofit a Band I-only set? Also, at the ITV start, BBC coverage was not yet complete, so in some parts of the country, initial TV receiver purchases would have been 13-channel models anyway.

Probably some of the numbers that would answer the above questions cannot not be deduced with any worthwhile accuracy, but it seems at least possible that within a few years of their initial availability, the number of 13-channel (as built) receivers in service easily exceeded the total number of Band I-only receivers. If that was the case, then easy access to the installed base would have been less of a reason not to start ITV on 625 lines.

I have found some further comments on the subject in a BBC brochure “Engineering Division” published August 1961 as a supplement to Ariel magazine. To quote: “In Britain, the world pioneer of high-definition television, a 405-line standard was adopted in 1936 when the service was started and the Government accepted the recommendations of Lord Hankey’s Television Committee in 1945 that the service should reopen with the same standards after the war. It should be remembered that at that time the 625-line standard, since widely adopted in Europe, had not been put forward. (In 1948 the Government announced that the 405-line standard would also be used for further stations.)”

The parenthetical part is interesting, as it implies that additional to the 1945 deliberations there was shortly afterwards another nodal point from which a different direction could have been taken, as by then the 625-line system was available. Or, it wasn’t automatic that the decision to reopen the London service on 405-lines implied that this standard would also be used for nationwide coverage. Conceivably there was debated the possibility that the UK could have followed the French pattern, that is retention of the established lower definition service in the capital but implementing a higher definition standard for nationwide coverage.

Also from the same brochure: “..an investigation was made into the respective merits of television standards based on different numbers of lines; a full-scale experiment to compare the relative merits of the British 405-line system and the 625-line system widely used in Europe was carried out recently and involved the installation of an additional high-power transmitter at Crystal Palace operating in Band V..” Presumably this study informed the early 1960s TAC recommendation and the subsequent Pilkington Report.

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Old 20th Mar 2011, 10:15 am   #97
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How many Band I-only receivers were in use just before 13-channel receivers came on to the market late in 1954? How many of these were retrofitted with Band III adaptors?
I think that the thing we tend to skate over is cost. A (new) TV was a major family investment not to be taken lightly, and having bitten the bullet the expectation was that it would last a long time. Certainly I knew of quite a few Converters still in use right through to the mid '60s.
Perhaps an alternative question would be 'When did Converters stop being made?'
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Old 9th Apr 2011, 6:47 am   #98
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Originally Posted by AlanBeckett View Post
Perhaps an alternative question would be 'When did Converters stop being made?'Alan
Good question. If we are talking of set-specific or make-specific converters that fed into existing IF strips, then it might have been the case that the manufacturers did one or two production runs and then kept the components in store as spare parts, perhaps for as long as spare parts generally were kept available for the models in question. It is conceivable that in some cases the remaining parts/converters were disposed of when the dual-standard age arrived, at which time fresh sets of conversion parts were needed for the then very recent 625-convertible receivers.

Moving on to a more general look at the 405 and 625 line comparison, it would be interesting to know what were the reasons for selection of the CCIR 625-line standard in Australia and New Zealand. Both countries, perhaps more so New Zealand, were still much British-influenced in the 1950s. As far as I know both countries looked at 405 as well as 625 lines before making a decision. In New Zealand the initial TV service was established on a minimum-cost basis, so 405-line system could have been attractive in that sense. Insofar as for many years TV receivers were locally manufactured by what was essentially a protected industry, then a choice of 405 lines might have made receivers just a little lower in cost, but in any event there was no need to worry about whether or not standard models from overseas would work. Most program material from overseas – a lot of it from the USA - came in film form so there were no compatibility issues to worry about there. Against that background, it is not unreasonable to assume that the choice of 625 over 405 lines was made for fairly compelling technical and performance reasons, notwithstanding the potentially lower cost of 405 lines. Typical receiver screen size might have been a factor. In the early monochrome days 23 inch was the popular size. But whether or not that would have been predicted during the standards deliberations is hard to say.

Cheers,
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Old 10th Apr 2011, 11:20 am   #99
neon indicator
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Default Re: 240, 405 & 625

Using 405 in 1946 was probably correct and obvious choice.

But (re-)starting TV at all before 1948 or 1950 was probably wrong.

If TV had been restarting in 1949 would it have been 405 or 625? More likely 625 with better option for UK makers (essentially similar model for export and domestic).

Note in the recent ISDB-T vs DVB-T debacle in South Africa, the local manufacturers wanted the wider DVB-T standard, and NOT a local version (different channel width) of the Brazilian version of obsolete Japanese ISD so as to have better export profits.

Ironically after years of 405/525/625/819 and PAL, PAL N, various SECAM, NTSC we have far MORE digital standards for SD and a huge number for HD instead of a single 48 fps 1154 line HD standard (to allow best Film transfer from 24fps).

Originally Analogue HAD to be 30fps 60Hz in USA and 25fps 50Hz in Europe due to making any Hum bar relatively stationary. Interlaced 24fps 48Hz would have made more sense for Film compatibility.

By Digital era frame conversion etc is working and PSUs are not an issue so having a single world wide 24fps based (maybe 48Hz or 72Hz refresh) single number of lines (600 SD, 1154 HD?) would have been possible.

In 1946 the 625 was still too embryonic, though Germans had used HD CCTV on rocket ranges and Russains doing 625 line tests.


If UK had waited till 1949, (and many, many countries didn't have TV till later and not all of UK by any means had TV by 1950), then 625 would have been a better choice. I don't believe the 15.625KHz Line frequency LOPT was a real issue, even with laminated rather than ferrite construction. It has advantage that much fewer people hear the Line Whistle than the quite obvious 10.125KHz whistle on many 405 line sets.

405 Colour was never viable.
Colour had been demonstrated as long as 1924 I think and was an inevitable development. From that point of view a 405 system was always going to be obsolete sooner rather than later.

Widescreen is another example of a technology too soon (like TV in 1946). It would have been better to not have WS TVs at all till HD was available as it actually degraded analogue (16:9 cropped and resampled into 4:3 frame, in 4:3, 14:9 or 16:9 format) and is reduced horizontal resolution for same height of screen and degraded 4:3 images on WS CRTs.

Obviously people never learn, introduce technologies a couple of years too soon and without enough thought.




I remember the start of BBC2 on 625 just outside Belfast. As kids we sat and watched the test transmissions. We were impressed by the extra quality on our dual standard TV. On UHF it had continuous tuning and a scale rather than fixed channel selections.

During the 1970s when still a school kid I repaired many Dual standard sets by soldering the switch in the 625 position. After BBC & UTV added to 625 lines I don't remember anyone sticking with 405 line on Dual standard sets. I did repair a number of 405 only sets too in the 1970s. These where invariably used as 2nd or 3rd sets. Some I got for nothing and sold cheap after repair. Usually faulty Dropper resistors, or mains rectifier or a valve.

The big wooden cabinets on some (but some 625 only sets had big wooden cabinets) gave nice audio. I remember one 405 set with corded remote and motor drive on channel change and a couple with FM Radio. I never remember any dual standard or 625 only sets with FM Radio or Remote up till about 1976 when I stopped fixing TVs. The first non-cable remotes I saw where on early Betamax and VHS machines, but 2nd stage electronic control panels rather than purely mechanical controls as on first models.

Last edited by neon indicator; 10th Apr 2011 at 11:26 am.
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Old 10th Apr 2011, 12:15 pm   #100
peter_scott
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Default Re: 240, 405 & 625

During the war Britain's radio industry was totally occupied supplying the needs of conflict. The loss of war contracts in 1945 would have left a very large hole with next to nothing to fill it if we had delayed television restart until 1949 or '50.

The nation was on its knees and the promotion of the idea that Britain still leads the world in technology was important to general morale.

It seems to me that restarting 405 was the correct decision.

Again, with widescreen, seen from a set manufacturers point of view you need to be introducing some new gimmick every now and then just to promote new sales.

Peter

Last edited by peter_scott; 10th Apr 2011 at 12:23 pm.
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