Talk:405-line television system

Half line

In the early days of 405, a line 1.5 lines long was inserted at the bottom of the frame. I forget the details of why, but something to do with synchronisation. This odd sized line was dropped fairly early in 405's history. Tabby (talk) 11:24, 26 November 2007 (UTC)[reply]

Almost. Aech odd field ended with half a line. The next field (an even field) commenced with half a line. Thus the two half frames of 202.5 lines combined to give a full 405 line frame. —Preceding unsigned comment added by 20.133.0.13 (talk) 12:50, 25 November 2009 (UTC)[reply]

Spot wobble

Interesting concept but surely if would have been a lot simpler to decreace the focus voltage slightly to produce a larger spot (and hence thicker lines) ? 80.229.222.48 (talk) 20:54, 15 March 2008 (UTC)[reply]

It would have been simpler, but it would have reduced the horizontal resolution. Spot wobble produced an oval dot which was higher than wide, in order to reduce the visibility of the line structure. --Harumphy (talk) 12:17, 12 May 2008 (UTC)[reply]

New Zealand?

Can anyone give a reference or further information on the New Zealand part of "was also used for some time in Ireland, Hong Kong and New Zealand" as this is the first time I've heard that New Zealand TV broadcasting was ever in anything except 625 line format, originally CCITT B&W, later PAL.Kiore (talk) 10:59, 12 May 2008 (UTC)[reply]

It wasn't; the NZ government briefly considered it, but came to their senses. I've removed this from the intro. ProhibitOnions ^(T) 11:24, 15 May 2008 (UTC)[reply]

Cessation of transmissions in the UK

I have a few questions about this which I think would be best answered by having someone knowledgeable incorporate the relevant information into the article.

When 405-line broadcasts were stopped in the UK, how many people were still using equipment that could receive them?
Perhaps a better question would be, how many people were still watching when the decision was made to finally cease transmission? And indeed, when was this decision made? Presumably feasibility studies were conducted to determine how many people would be inconvenienced by it, so there will be figures in print somewhere.
When were 405-line televisions last manufactured and sold? i.e., how antiquated did you have to be to one of those who ended up with a blank screen in 1985.
Given that 405-line had better geographic coverage, were some people in remote areas left without reception after the switch-off, or was there a building programme in the 1970s and 80s to provide new transmitters so that the 625-line coverage problem was resolved in advance? If so, which transmitters are a legacy of this project?
Finally, what specific frequencies were used to transmit 405-line television? Was there any particular reason, technical or otherwise, for having them on VHF and 625-line on UHF? The article says they were sold off for DAB and trunked PMR, so there must be a specific band or bands with known bounds. Presumably people are listening to DAB right now on the same frequencies that they once watched 405-line television on!

Thanks. Beorhtwulf (talk) 20:50, 23 August 2011 (UTC)[reply]

Re first point, when I worked at the BBC (Publications) in 1985, I was told by an engineer that the Hull area VHF405 xmitter had developed a fault in the previous year, and ceased to broadcast, and it was only discovered three months later when a single user (a elderly lady) complained. This accelerated the decision at BH to switch off VHF. Maybe someone at BH Eng can expand. Interesting to contrast the main analogue switchoff recently, where a formal campaign was used.