response 98 of 210:

Sep 17 11:01 UTC 1998

You can't inject a digital signal at the volume control, Scott.  All
you would get is buzzing.  Besides, the digital signal would be at least
8 bits.  Where would you put them all when tapping into a stereo receiver?
(The signal that comes out of your CD player is really analog.  The
digital signal on the CD didn't spend much time being digital once it
was read by the laser.  from there it goes to a digital to analog converter
(A to D) and the rest is all old fashioned analog circuitry.)

Cool! 2320-2345 MHz is not far from the 2.4 GHz microwave oven band!
Perhaps I can re-tune the cavity on my $5 garage sale special microwave
and be the first on the block transmitting digital audio!  ;-)

response 100 of 210:

Sep 17 15:11 UTC 1998

Sure. Back when I was a teenager I was tapping audio signals into the
volume controls of (tube) radios, as a convenient amplifier. Had to watch
out, though, as those radios had no power transformers and plugs weren't
polarized, so the 'hot' side of the line could be on the chassis and
circuit ground.

response 102 of 210:

Sep 17 20:34 UTC 1998

So can you somehow pick up digital signals with some sort of antenna and then
feed them into the CD player, at the point where it is about to convert the
digital to analog?  Would it be efficient to make a combination CD player cum
digital receiver?  Maybe also combined with a digital tape reader?

response 104 of 210:

Sep 18 04:02 UTC 1998

Sindi:  "digital" is just a generic description for the technique of 
sampling data and storing it as a computer file.  There are lots and 
lots of digital formats out there; the audio CD standard is just one.
Each format has its own software for decoding and playing the computer 
files -- in a home CD player, that's usually packaged in a chip.
But a CD player chip is going to be useless for decoding the Real 
Audio format, or a .WAV file, or a MP3 file.   It's only good for 
decoding the CD Audio format. 
 
It's unlikely to be easy or cost-effective to build a digital 
radio receiver by hacking a CD player and a conventional radio.
It's not likely to be possible at all; you'd probably be better off 
buying the chips, when the standards are announced, and assembling
the radio yourself as a hobbyist project.  The chips are going to 
be very cheap, if digital radio gets off the ground..

response 106 of 210:

Sep 18 15:36 UTC 1998

Gack! (Excuse me.) Read that Radio Amateur's Handbook - there is probably
an old one in the Kiwanis books for sale. All radios use variable capacitors
and/or inductors to "tune", but there is a wide variety of ways to do this.
You'll find schematics in - YES! - the Radio Amateur's Handbook.

response 108 of 210:

Sep 18 17:16 UTC 1998

schematics for a digital tuner?  In an old handbook?  omni gave us one.
Kiwanis tends not to get such valuable books.  I made an AM radio once in
physical chem lab, with a 9 volt battery in it.  What are the parts for a
digital tuner likely to cost new, and which ones are available in used tuners?
Maybe Kiwanis could be the first in town to sell digital tuners!

response 110 of 210:

Sep 18 21:16 UTC 1998

I know a radio engineer from Bosnia who could help by email.  We don't plan
on actually designing the tuner, just following a schematic and maybe
modifying it a bit to use the parts we already have (dead receivers, an
occasional dead CD player, VCR, must be something useful in them).
Seriously, would someone want to take a crack at explaining how tuners work?
We have been repairing only the amplifier parts of receivers.  I could not
understand enough of the vocabulary in several books I looked at to figure
out the tuner part, other than that somehow the carrier signal has to be
subtracted to leave the information part, and I think the signal got amplified
a bit before reaching the volume control.  And how would digital tuners differ
from analog?

response 112 of 210:

Sep 19 12:20 UTC 1998

My prediction is that a complete tuner will be cheaper than the individual
parts.  THere are precendents for that...

Seriously, unless you plan to become an electronics engineer with computer
engineering skills, the most you'll be able to do is an easy change like
adding a line out to a digital "walkman" style portable tuner.

response 114 of 210:

Sep 22 20:36 UTC 1998

Yup, cheaper new.  You'd be suprised what economies of scale vs. cost of small
parts distribution adds up to.  For a laugh, try addingup the cost of a new
transmission for acar vs. cost of all the parts to build the same tranny.

response 116 of 210:

Sep 23 10:36 UTC 1998

In part because many of the parts are custom made for the manufacturer and
pinouts and specifications are not available to the public.  In part because
the part you salvage may be out of spec., physically of the wrong size, or
have leads too short. Because the equipment to test and align what you made
will cost many thousands.  Because the parts you need may not be available
form the surplus on hand.  Heathkit went out of the kit business because
it was cheaper to buy all done and ready to play than to build it from
a kit.  To top it off, often what you wound up with was an inferior product.

response 118 of 210:

Sep 24 09:51 UTC 1998

Don't feel bad.  I have a pretty extensive knowledge of electronics and
even I will wait to buy one rather than build one.  If you want to listen
to more free audio, look into one of those 6' to 8' dishes used to receive
satellite TV.  Many of the TV channels carry audio on one of several 
subcarriers.  All you need to decode them is a stereo decoder, designed for
the task, or a good HF receiver added to the TV system.  BTW, does Kiwanis
have used satellite TV equipment?

response 120 of 210:

Sep 25 09:57 UTC 1998

See there?  You could do this for free!  There are hundreds of audio
programs on satellite. (I'm not talking Digital Cirect Satellite, I'm
talking about the big dish satellite. Not the same as cable either.)
A colleague here at work does a lot with satellite equipment that he
picked up for very cheap.  He showed me the book on satellite audio
the other day.  You could put one of those dishes on the house you are
building and the neighbors would be absolutely convinced that you are
really building a rocket ship ;-)