"Engineering Announcements" (UK IBA History)

  • Well, this thread is probably going to end up as technically useful as the Sat Humour thread, and maybe no-one out side of the UK will recognise the image or the joke, but,I have heard it suggested to use Wednesdays UTC as an 'Experimenters Day'.


    Well in any case, any G's, M's, or 2E's recognise the attachment ? :) Or at least something similar ? Do you remember the Engineering Announcements aka Ghost Programmes ? I was thinking of adding PID information for what I'm playing with on any particular Wednesday. Anyone up for generating something similar (Along with Testcards..) ?

  • g7iii

    Changed the title of the thread from “"Engineering Announcements"” to “"Engineering Announcements" (UK IBA History)”.
  • I don't remember Engineering Announcements but I do remember Engineering Tests!

    In the old days when I happened to watch TV in the middle of the night I sometimes saw strange experiments on BBC, e.g. experiments with encryption and programmes intended for automatic recording and later playback.

    As this was in de days of Analog TV, the encryption usually involved the wellknown inverted-sideband audio.

  • pe1chl : Oh wow! "Inverted Sideband" I'm guessing that was the ROT13 of it's day (IE absolutely useless) ? During these times in the UK, the independents (ie *NOT* the BBC [aka 2LO once upon a time when they where 'amateur'!] were just starting, and very regulated


    I'm sure google has some of the test cards that you probably received! I say resurrect something similar!


    73s


    Iain

  • Well, of course you did require some equipment to make the audio understandable, without that you could only hear the cadence of the speaking and not understand much of it.

    I'm talking about the 1980's here, that was when we got cable TV and BBC1 and BBC2 were added to it. It was received in Belgium and relayed via microwave links to the Netherlands. There was also a receive station in the Hague I think.

    BBC clearly were experimenting with targeted material for subscribers with a box, e.g. for company internal news and instruction videos.


    In those days we had a movies channel on cable that required a separate subscription, FilmNet. It was encrypted as well, it used a method where the frames were alternately normal and inverted in polarity and the area around the sync pulse was level-shifted back into the normal video levels. A sync signal was transmitted as AM modulation on the audio subcarrier instead.

    The audio itself was not changed, but usually a TV would mute the audio anyway when it could not achieve sync.

    There was a control signal on one of the invisible lines that told the decoder if the upcoming frame is normal or inverted.

    And then there was a separate data channel at a completely different frequency (75 MHz) to enable/disable the boxes addressed by serial number.

    All in all it was quite complicated, and of course the channel had to provide those boxes to the subscribers for free and recoup them from the monthly fees.


    And then there were those electronics hobbyists that just cobbled together a decoder from surplus TV modules (tuner, IF, rf-modulator) and some CMOS electronics. Oh well...