Quote:
Originally Posted by Jay
Very interesting. The technology was there for HD, but ......... analog high-line-rate systems require lots of bandwidth. |
Bingo! Cost was not an issue, it was bandwidth. In 1948 the US had run out of allocations for most VHF channels. There was a freeze put on new stations that lasted until 1952 (I may be a few years off on dates, so correct me and save me the googling).
The die was cast by that point. 6MHz wide channels were needed for 480i analog transmissions.
One thing I find repeatedly and is still common is people under the age of even 40 almost now don't realize RF Spectrum is LIMITED!!!!!!!!!!!!! There is ONLY so MUCH!! You can't add and add and add services to RF services without either displacing a previous service or sacrificing quality.
In my opinion having worked on digital television since 1978, the electronics were not ready for broadcast until the early 1990's. It wasn't until the mid 80's programmable chips were cheap and available. Micron level geometry on a chip surface wasn't available commercially yet and what we had was expensive.
Sure I was doing digital TV in the 70's but with TTL chips that pulled massive amounts of power. The memory to store just 2 fields of
NTSC was the size of 5 modern full size computer cases crammed full of memory chips. I have forgotten but they were either 256 or 512 byte chips. They were 8 bits wide. Each card held 120 of them and there were 32 cards in the machine. It held 1/30 of a second of TV. But that was enough for us to manipulate the video. The box sold for 1/4 million dollars and required a 50 amp service at 120 VAC. It took a full 6 foot rack to mount all the equipment.
I then worked for another company that compacted the size of it in 1985 with the latest chips. It was 1/6 the size all fitting in about 8 rack units or about 30 inches tall. It would run on a 20 amp service. Still that box was $100,000. That was state of the art, we had no competition.
Basically it wasn't until MPEG2 and micron level integrated circuits came along that a home TV could even be considered.
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PAL or Phased Alternate Lines was adopted in most of Europe that was both wider and taller than our standard. It took an 8 MHz channel. There was little VHF done in Europe and most of them moved to UHF by the 1970s where 8 MHz channels were much easier to expand. They also have smaller countries so UHF was well suited, without vast expanses of rural areas.
But this sure left them much better suited for the
digital transition than North America. Mainly for 2 reasons even if you forget DVB is better than
ATSC.
1) Everything was already UHF
2) Converting analog
PAL channels to DVB channels they had 8 MHz bandwidth. This alone gave them 33 percent more room to run subchannels.
But yet back on topic it can be looked at in another way that even with 576i standard of
PAL, it ate up 8 MHz of bandwidth. Still limiting the number of channels available to a country even with one network each (most common back then in Europe). Still to cover the countries they needed more than one channel. The wider channels in Europe also helped convince them to move to UHF where there was more room. So it was a curse at first that later turned into a blessing, at least for their geography.
Going Back to the Beginning of HDTV
Linear Mode
