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| Author |
Message |
| 25 new of 210 responses total. |
scott
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response 75 of 210:
| 
Sep 10 23:02 UTC 1998 |
There have been FM receivers that convert the signal to AM, for car radios.
But I'd figure people would either buy a tuner with audio out, or else new
Walkmans. Not much convenience in carrying two boxes around...
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keesan
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response 76 of 210:
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Sep 11 13:12 UTC 1998 |
My radio just sits there, I don't carry it around.
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kentn
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response 77 of 210:
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Sep 11 18:09 UTC 1998 |
The real reason to get a whole new receiver will probably be cost, or
rather, pricing. To get you to buy a new receiver (radio, tuner, etc.)
they'll likely set the price of conversion units high, at least at first
(until competition heats up, assuming there is a market for converters).
Seems that's the likely route for digital TV convertors, too. Of course,
they may also set things up so that the sound/image/whatever of a
convertor is *not-quite* as good as the new full unit, and that may
influence a lot of buyers to junk their old sets (even if the quality
difference is not noticeable).
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krj
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response 78 of 210:
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Sep 13 18:22 UTC 1998 |
I saw a web news article which was from the same source as what
keesan heard in resp:72 . Alas, I have been unsuccessful in finding
the article again. This article mentioned the frequency bands which would
be used for digital radio: what I found discouraging is that the
two countries are going to use different frequencies. No more of this
sloppy cross-border broadcasting!
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keesan
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response 79 of 210:
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Sep 13 18:37 UTC 1998 |
What bands are these, and will receivers be able to receive both bands?
We listen to CBC a lot.
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danr
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response 80 of 210:
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Sep 13 21:58 UTC 1998 |
It's highly unlikely that you'll be able to purchase an adapter to use your
analog radios to receive digital radio signals. The modulation schemes are so
different that the converter would probably cost just as much as the entire
radio.
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keesan
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response 81 of 210:
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Sep 14 16:07 UTC 1998 |
How long are stations likely to continue broadcasting analog? Perhaps we
should have a half-price sale on radios at Kiwanis. Looks like everything
is going to end up being digital - CDs, digital tapes, digital radio.
Mono radio is still around, possibly because it comes in more clearly from
a distance than stereo, or is it something that has to be broadcast in order
to broadcast a stereo signal?
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rcurl
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response 82 of 210:
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Sep 14 17:24 UTC 1998 |
Stereo is two signals broadcast separately in such a way they can be
demodulated apart from one another. With the analogue modes that means
broadcasting on different frequencies. With digital modes the packets just
have to be coded 'right' and 'left', and can be broadcast on the same
carrier.
I've been wondering if spread-spectrum is going to come into use. It is
used in the GPS network. All the satellites broadcast in the same
frequency band but the different (digital) channels are separated not by
coding the packets but by modulating them with a pseudo-random code, which
is used to separate the channels in the receiver by cross correlation.
This way, essentially any number of channels can be broadcast on the same
band. At the frequencies used the cross-correlation can be done fast
enough and accurately enough to produce perfectly respectable audio. The
advantage is extreme resistance to interference and noise.
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keesan
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response 83 of 210:
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Sep 14 19:14 UTC 1998 |
With an infinite number of channels, are we likely to have any new classical
radio stations? What will it cost to set up to broadcast digital?
Rane, could you expand on your second paragraph for the technically
challenged? Pseudorandom code? Cross correlation?
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scott
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response 84 of 210:
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Sep 14 22:02 UTC 1998 |
Pseudo == fake
random == random
Pseudo-random means "as random as computers can get, cheaply".
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rcurl
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response 85 of 210:
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Sep 15 06:34 UTC 1998 |
The GPS signal is PM - phase modulation: the carrier is a 1575.42 MHz sign
wave that is flipped + to - and - to + depending on whether the message
bit is a 1 or 0. In addition, the carrier is also flipped +/- *randomly*
with a random succession of 1s and 0s that is generated as a pseudo-random
binary signal. Pseudo means that the random sequence is generated
deterministically using a "seed" number to start it. With the same seed,
the same sequence of random 1s and 0s are generated. You can do this
simultaneously with a larger number of different pseudo-random sequences
for different messages to be broadcast simultaneously on the same band.
The signal is recaptured by multiplying it by the same pseudo-random
sequence as was used to generate the message you are interested in. The
multiplying and averaging is called cross-correlation. The cross
correlation of all different pseudo-random sequences approaches zero,
leaving only the auto-correlation of the pseudo-random sequence with
itself. This will be the original carrier coded with the message.
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n8nxf
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response 86 of 210:
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Sep 15 12:40 UTC 1998 |
I will be able to listed to digital radio just fine on my 1970's vintage
component stereo system. I will just have to add a digital tuner to it.
It already has a CD player attached to it. Doing this with a all-in-one
radio would not be worth the cost and time required to do the modification.
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keesan
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response 87 of 210:
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Sep 15 21:37 UTC 1998 |
Any suggestions on how to convert a CD player to a digital tuner by adding
parts from an obsolete analog radio?
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kentn
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response 88 of 210:
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Sep 16 02:37 UTC 1998 |
Is a "sign wave" the same as a "sine wave"?
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rcurl
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response 89 of 210:
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Sep 16 03:35 UTC 1998 |
In a way. A sign wave is one that shifts in sign. A sine way does that,
but not in the way a phase modulated carrier does. Therefore that carrier
is not a sine way but a sign wave.
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n8nxf
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response 90 of 210:
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Sep 16 10:13 UTC 1998 |
r.e. #87. I doubt that your average person will have the knowledge to do
something like that. The width of the IF, the effect it has on the phase
of the signal and the frequency of the LO are all different. Not to mention
trying to figure out where to inject the signal into the CD player and at
what level.
I think they do the sign wave at the stadium?
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rcurl
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response 91 of 210:
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Sep 16 16:40 UTC 1998 |
Also at political conventions. These are all examples of phase modulated
signaling.
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scott
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response 92 of 210:
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Sep 16 16:41 UTC 1998 |
Well, you could inject an audio signal at the volume knob; that tends to be
a pretty good place (I've put CD jacks into car radios that way).
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rcurl
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response 93 of 210:
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Sep 16 17:26 UTC 1998 |
How does that create a digital tuner (which is what #87 asked, if I
am not mistaken)?
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keesan
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response 94 of 210:
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Sep 16 20:43 UTC 1998 |
Could you possibly just get the signal from the antenna and inject it at the
volume control, or should be be amplified a bit first? How strong a signal
does a CD player deliver to the volume control (of the amplifier?). Would
it help to inject the signal into the phono input, which usually has a preamp
attached? I presume the signal from the antenna has to go into the CD player
somewhere - I don't recall any volume control in a CD player. Where would
it be injected and does it need processing first?
(Sorry about any dumb questions, I never did understand radios).
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scott
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response 95 of 210:
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Sep 16 21:38 UTC 1998 |
er, getting the signal from the antenna to the volume knob has been quite
complicated for decades now. It's been a long time since the "cat whisker"
days of receiver design.
How good are you at creating your own IC chips? Cause that's where you'd have
to start for digital radio, most likely.
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krj
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response 96 of 210:
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Sep 16 22:18 UTC 1998 |
Found it!!! I got this from the FCC's web site, by searching on the
terms "digital radio canada". The actual URL is too long and painful
to type in... I am reformatting it for 80 column width.
It sounds like the USA and Canada are going to implement two different
services.
----------
Report No. IN 98-50 INTERNATIONAL ACTION September 3, 1998
THE UNITED STATES AND CANADA AGREE ON CONDITIONS FOR
IMPLEMENTATION OF
U.S. SATELLITE DIGITAL AUDIO RADIO SERVICES (DARS)
AND
CANADIAN TERRESTRIAL DIGITAL RADIO BROADCAST SERVICES (T-DRB)
ALONG THE U.S./CANADA BORDER AREA
The United States and Canada have agreed on technical conditions
for implementation of Terrestrial Digital Radio Broadcasting (T-DRB)
services in Canada in the 1452-1492 MHz band and Satellite Digital
Audio Radio Services (DARS) in the United States in the 2320-2345 MHz band.
As a result, T-DRB service can be implemented immediately, and the
launch of DARS can occur after a transition period.
Coordination discussions regarding DARS are continuing with countries
other than Canada.
These agreed upon conditions are the result of negotiations that
took place over several years and involved complex inter-service
frequency sharing considerations unique to the U.S. and Canada
in these two bands. Although these bands are used for different
services in Canada and the U.S., new applications of digital technology
will be introduced by Canadian and U.S. providers. It is important to
note that the continued operation of U.S. aeronautical telemetry
stations was a paramount concern in these discussions.
Looking to the future, FCC Chairman William E. Kennard, stated,
"This successful negotiation will provide U.S.consumers access to
innovative CD quality audio programming and will promote new
communications services using innovative satellite-delivered
digital technologies."
U.S. Ambassador Vonya McCann and Canadian Assistant Deputy Minister
Michael Binder exchanged letters that will allow both countries to
begin to implement by September 1, 1998 the technical conditions for the
introduction of these new digital sound broadcasting services
on either side of the border. Both the United States and Canada
have pledged to work swiftly to convert these technical
conditions into binding international agreements.
In the interim both countries will implement these mutually
agreeable conditions on an interim basis, beginning on September 1, 1998.
Details of the conditions are available on the FCC internet
site for the International Bureau (http//www.fcc.gov/ib).
For further information, contact Ronald Repasi, (202) 418-0768,
Rosalee Chiara (202) 418-0754 or
Larry Olson at (202) 418-2142, of the International Bureau.
- FCC -
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rcurl
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response 97 of 210:
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Sep 17 00:05 UTC 1998 |
Re #94: keesan, get an old Radio Amateurs Handbook, and read the
elementary explanations in that of how radio works.
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n8nxf
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response 98 of 210:
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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! ;-)
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scott
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response 99 of 210:
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Sep 17 14:32 UTC 1998 |
Er, I wasn't the one asking about putting digital signals into the volume
knob. I was the one saying you could tap a digital tuner into the volume
knob, though.
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