OT: Retro radios

[Gene E. Bloch]

Mind
you, I've always been surprised that portable CD players (Walkman etc) were
feasible, given that the laser needs to follow very narrow tracks and so
powerful (ie power-consuming) servos would be needed to keep the beam
accurately on track as the mechanism was jolted while jogging or when
driving over bumps. In a car, power consumption is not too much of a problem
but in a portable device, battery consumption would be an issue.

They require very little power, thanks to clever design.

Small movements are controlled by voice-coil or piezo actuators that use
little power, and larger movements are prevented by the screw drive that
keeps the laser more grossly in position based on feedback from the
sensors that drive the voice coils.

 

[pjp]

Geeeeez........now I've *GOT* to get one of these for the van too!!!!!
(Although they look far more 50's than 60's.)

<http://www.google.com/search?q=car+record+player&hl=en&client=firefox-
a&hs=HlP&rls=org.mozilla:en-
USfficial&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=SA-
ZULqqEOfW0gHEs4GIBw&ved=0CB8QsAQ&biw=1054&bih=656>

There seems to be only a couple on e-bay.....and possibly going for more
than I paid for the Supertuner 1.

I remember that period, being 62 tomorrow. What I also remember is that
I lucked out and found a car cassette deck at the beginning of the 8-
track craze. Cassettes weren't as common but could be had without that
much effort and it wasn't any more uncommon someone had a home cassette
recorder versus a home 8-track recorder so recording vinyl to take in
car wasn't that much of an issue.

What bothers me thinking back thru that period was essentially both 8-
track and cassette were available at the same time. Cassettes were
obviously the better media for both quality and durability. That said,
instead the music industry milked as much as possible out of the 8-track
market before abandoning it in what appears to be nothing more than a
greedy attempt to have people repurchase the same music.

I've paid my dues, bought enough tapes and vinyl (1000's) that I refuse
to feel guilty for ripping or even downloading some song from a day long
enough gone that in my opinion the music should be "common property" by
now.

 

[J. P. Gilliver (John)]

[IIRR Walkman was a cassette machine, though they _may_ have continued
the name - though I _think_ they used Discman.]

They require very little power, thanks to clever design.

Small movements are controlled by voice-coil or piezo actuators that use
little power, and larger movements are prevented by the screw drive that
keeps the laser more grossly in position based on feedback from the
sensors that drive the voice coils.

Also, they _don't_ track that well; for the last quite a lot of years,
they rely on buffering. There was a time the amount of buffering (say,
20 or 30 seconds' worth) was something the manufacturers would boast
about, especially in machines aimed at the jogging market. Basically,
the player runs a little faster than nominal x1 speed, so that it fills
a buffer, which is then played from at x1 speed; when a knock causes the
read assembly to go off track, there is enough in the buffer for playing
to continue until the mechanism has found its place again (at which
point it starts to fill the buffer again). When the buffer is actually
full, then the disc reverts to x1 speed, so that the buffer is being
filled at the same rate it is being emptied. IIRR, there were some
machines where you could turn the buffering off, if the unit was being
used in a stationary position, to save power, since the extra motor
speed - and running the buffer electronics - used more power; I suspect
this isn't offered any more, since cell capacities have improved and the
power consumption of memory management has dropped.

 

[Gene E. Bloch]

[IIRR Walkman was a cassette machine, though they _may_ have continued
the name - though I _think_ they used Discman.]

They require very little power, thanks to clever design.

Small movements are controlled by voice-coil or piezo actuators that use
little power, and larger movements are prevented by the screw drive that
keeps the laser more grossly in position based on feedback from the
sensors that drive the voice coils.

Also, they _don't_ track that well; for the last quite a lot of years,
they rely on buffering. There was a time the amount of buffering (say,
20 or 30 seconds' worth) was something the manufacturers would boast
about, especially in machines aimed at the jogging market. Basically,
the player runs a little faster than nominal x1 speed, so that it fills
a buffer, which is then played from at x1 speed; when a knock causes the
read assembly to go off track, there is enough in the buffer for playing
to continue until the mechanism has found its place again (at which
point it starts to fill the buffer again). When the buffer is actually
full, then the disc reverts to x1 speed, so that the buffer is being
filled at the same rate it is being emptied. IIRR, there were some
machines where you could turn the buffering off, if the unit was being
used in a stationary position, to save power, since the extra motor
speed - and running the buffer electronics - used more power; I suspect
this isn't offered any more, since cell capacities have improved and the
power consumption of memory management has dropped.

Thanks for the reminder. I had plumb forgotten that...

 

[Ian Jackson]

Digital Audio Broadcasting - what the UK powers that be call the mp2
broadcasting used in the UK (and, I think, most of the rest of western
Europe, though [a] they don't call it that, they don't cram in so
many stations, so it is genuinely good quality, [c] some countries are
also I think broadcasting using better [more efficient] digital audio,
such as AAC).

Would that be what's called HD (Hybrid Digital) radio in the US? Never
seen a set that would receive it (haven't really searched, though).

No. DAB is purely digital. It is totally incompatible with analogue
reception.

Several (some would say far too many) digital radio programmes are
multiplexed into QAM transport streams, which are broadcast in the old
'high-band' TV band, around 200MHz.
http://en.wikipedia.org/wiki/Digital_Audio_Broadcasting
http://www.st-andrews.ac.uk/~jcgl/Scots_Guide/RadCom/part22/page2.html
http://www.jimsaerials.co.uk/dab & fm/radio.htm