Must admit, the technology is awesome. Who would have thought it possible a few years ago.
Another thing I find amazing - CRT Colour TV. How on earth did we get the technology so refined that we could mass produce such a convoluted way of giving a colour picture of the quality we ended up getting.
"Cue Cadbury Smash Aliens "Aim and electron beam down a glass tube to excite a phosphor dot - Ah Ah Ah!"
by taking advantage of the fact that the picture is "moving" to trick the eye into thinking it is better than it really is
tim
There are two separate issues:
(1) is mainly manufacturing tolerances and linearity of electronic control signals (focus, beam deflection).
(2) is the really amazing one: the use of a colour sub-carrier that causes the spectrum of the colour information (which mainly occurs at multiples of the line rate) to interleave with that of the luminance signal (which has a similar spectrum) by use of f(sc) = (f(line)+1)/2, together with vestigial sideband AM to give full colour bandwidth for one sideband and low-pass-filtered sideband on the other. Making sure that none of the newly-introduced signals interfere with the existing luminance signals, so choose a sub carrier that causes a dot pattern that moves rather than being stationary (to make it less noticeable). And then using quadrature modulation so the U and V signals are modulated about the same carrier but don't interfere with each other.
And then we have the PAL improvements over NTSC to prevent phase errors manifesting themselves as shifts in hue (they only cause error in saturation which is much less notceable).
But then we get onto the encoding of digital TV signals into interleaved MPEG streams, COFDM encoding, pseudo-random encoding to make the digital signal look like noise with no discernable pattern when received on an analogue TV (that factor is no longer needed!). I wonder how big a DTV receiver would be if it had to be constructed with discrete transistors, resistors and capacitors, without the benefit of integrated circuits.
Those hoverboards would be more awesome if they actually hovered:-)
Today apparently shoplifters are using the hoverboards to help them nick stuff fast. Trouble is the less expert people usually end up in a big heap on the ground with a big security guard looking down at them in that way they have that indicates You stupid boy... as for crts, it was gradual. Remember the basic cathode ray tube, love the oldfasioned name, was very old indeed, but the colour system was I believe invented by some RCA bloke one day, who realised that the shadow masked itself could be used to indicate where the phospher dots needed to go. It was done photographically I believe. Very power wasteful though when you consider a lot of the beam is obscured on each gun. Brian
On your last point I can only point you to what happens if, of example even a computer from the 1980s logic arrays are simulated by ordinary logic chips of the time the resulting pcb would no longer fit in the box. Another example was good old fashioned teletext of the old sort. The first boards made were huge crammed with chips. Pye Labgear made an adaptor just for teletext in the early days. As it also contained a tv minus the display, it was as big as an early video, and the tifax decoder made by Texas Instruments was more than a foot square crammed with chips and took a lot of current. However only five years on and the whole thing was in one tiny chip fitted inside most tvs. Brian
Yes but the idea is a good one. I do feel though that all of those devices are a bit dangerous in crowds and indeed around us blind folk. they are actually illegal and of course if you have an accident in one you are not covered by any insurance either. Brian
Never mind tellys, I still marvel at the very radio waves themselves!
As for a crystal set, I find it's so wonderful in its sheer simplicity.
Especially the Delta guns where 90% of the power ended up heating the shadow mask. Some were made of Invar to reduce distortion.
Nearer to magic than science! Loved making them as a kid.
Tim
I tried to breath in that same sense of wonderment about a crystal set into a 15 year old relative of mine. I may as well have been talking Chinese. He simply couldn't understand why anyone wouldn't use their smartphone and stream audio from the net.
I can only hope my young relative is a one-off in his lack of curiousity.
Hopefully other youngsters are far more inquisitive and would show real interest. Or maybe not? Tell me.
In message , pamela writes
Difficult. I think school has an influence, but we're lucky. Son attends a rural Comprehensive in NE Scotland, with one non white face, everyone speaks English (or Scottish!) as their first language and class sizes are small (
I'm sure not all kids were all that bothered about crystal radios 50 years ago either, different things float peoples boats. We are a bit of a self selecting demographic on uk.d-i-y I suspect.
Also, there is the wider context. We are much less likely to be fixing things at home nowadays, so there is much less of a culture of tinkering with things and kids are much less likely to be exposed to it.. I think there is also something about the distance between the technology you can fiddle with and the technology around you. Maybe a crystal radio is to far divorced from the world of smartphones, to seem of any relevance, unless you have an interest it that sort of thing.
TBH I doubt that either of our daughters (11 and 14) would be that interested in a crystal radio. Even though they are both fairly technically minded. (I helped the 14yo fix her phone the other day and the 11yo loves fiddling with things, making stuff etc.)
The thing is that we could make a crystal set - the youngsters cannot make a smart phone.
Good point. When I was a kid, I built loads of HeathKit equipment, including our first colour TV. Seeing each component, and understanding its relationship to others made understanding how things worked, much easier. Today's chips are harder to understand.
Probably still possible to make a primitive FM or AM radio..
Reaction sets are fun, and can even do FM, albeit without the noise rejection of am. But getting radio stations is a non-challenge these days.
NT
With luck one day he will graduate to those iPhone teardowns which examine the components used. I like them.
There's something about the wonderment of a crystal set which is closer to meditation than being startled by impressive function from modern technology. Sort of a chilled contentedness rather than stimulation seeking. I hope one of your daughters can find that one day.
I was staying in the spare room at my parents a couple of weeks ago, having taken the niece and nephew there for the weekend. In the bookcase were a few of my old Ladybird books, including the one on building a transistor radio. Finding an OC70 might be hard today, but it could be updated to use silicon transistors. I did wonder how much longer there would be any AM radio signal which can be detected with just a diode.
I did build some of it as a child. However, I'd already managed to repurpose an old intermediate frequency transformer into a tuned circuit to pick up Radio 4 using an aerial wire the length of my bedroom, which could power a crystal earpice from the aerial power alone. Spent ages in bed listening to it when I should have been asleep ;-)
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