karn@allegra.UUCP (Phil Karn) (01/19/84)
Is anyone familiar with the standards, if any, in use by AM stereo broadcasts? My interest is academic; I'm certainly not going to rush out and buy a receiver. Phil
fish@ihu1g.UUCP (01/20/84)
There are a few systems under contention for this "boon," all of them
mutually incompatible. I have an old "Stereo Review" that describes these
in more detail; I'll be glad to post a synopsis of the article if there
is more general interest. However, you can look for this one to go the
way of Quad and the Elcassette. I don't know if there are any stations now
broadcasting AM stereo in this country. My comment on this is, "why bother?"
AM is generally a noisy, severely compressed signal, of no interest to
lovers of true high fidelity.
As for the gaggle of competing systems, you can blame the FCC for not getting
off its big, fat, bureaucratic arse and ruling on ONE standard system. They
are also the reason we won't have Stereo TV sound for at least another decade.
If more than one system is approved, manufacturers will have to produce
equipment compatible with all available systems, at a resultant higher cost
to the consumer. This is called "fostering competition."
Bob Fishell
Boy, am I in a rotten mood today!gayde@iwu1b.UUCP (01/21/84)
I know that WJR-AM 760 in Detroit advertises itself as "AM Stereo".
I haven't heard them in stereo, though, so I can't comment on the
sound quality.
--
Peter Gayde ihnp4!{iwu1b,ihuxp}!gayde
AT&T Technologies
Naperville, IL
(312) 979-7186kevin@beesvax.UUCP (01/21/84)
KSL radio here in Salt Lake City broadcasts in AM stereo. I was under the impression that the FCC HAD decided on a standard for AM stereo before KSL started stereo broadcasts. KSL has numerous contests where you can win an AM stereo receiver and they have set up demonstrations at a few local hi-fi shops where you can hear AM stereo. However, I agree with Bob Fishell that this to will pass. Kevin Heaton Beehive International ... harpo!beesvax!kevin
edhall@randvax.ARPA (Ed Hall) (01/24/84)
---------------------------- An AM station just south of the border here broadcast in `AM Stereo' for a few months about 12 years ago. Although a Mexican station, the signal was beamed Northward and was pretty easy to receive in the LA area; it had an `easy listening' format and anouncements were in English. The technique used consisted of modulating the upper and lower sideband of the signal with the left and right stereo channels. By tuning two AM radios slightly off-center, one above and the other below the carrier, a moderate amount of stereo separation could be obtained. (Actually, tuning an AM radio off-center often results in better frequency response, as the bandwidth of the receiver is usually rather small, and tuning so that the carrier is towards the top or bottom of the passband allows higher-frequency information from one sideband through at the expense of the other (usually redundant) sideband.) This mis-tuning increased distortion and noise a bit, but the spaciousness of the resulting sound was unmistakable. A bit of a pain to set up, though, as most households don't have two similar AM radios easily placed in a stereo configuration. This might be the reason the broadcasts were discontinued; I never did find out just what happened to the station. The bandwidth required for this sideband technique is theoretically considerably more than a normal AM signal, although passband filters at the transmitter can reduce this at the expense of increased distortion. Several of the newer AM stereo methods use a similar technique, but reduce the bandwidth in other ways by various (incompatable) encoding schemes. -Ed Hall decvax!randvax!edhall edhall@rand-unix
dwl@hou5e.UUCP (D Levenson) (01/26/84)
WQXR is a classical music radio station owned by the New York Times. It advertises itself as being the first AM Stereo classical station in the country. (PS: They have had FM stereo for years.)
shacklet@ittral.UUCP (Cliff Shackleton) (01/30/84)
I recently heard a demo of the motorola AM stereo sys-
tem (CQUAM) at the winter CES show. It was
impressive,however they had their own transmitter; I don't
know if they were operating at legal bandwidth.
They were promoting the fact that they were the system
chosen by DELCO and had an Olds Cutlass set up as a listen-
ing room.
The preferred bandwidth response of the receiver is 10
KHz but the demo units had a wide and narrow bandwidth
switch on them to accommodate stations broadcasting a preem-
phasized signal.
The People at the display were very helpful and in fact
gave me data sheets on their decoder IC (MC13020) and two
samples of the part to boot!
I have not built up the circuit yet (I am trying to
scrounge up a 3.64 mHz ceramic resonator) but do have two
stations in the Raleigh area broadcasting the signal.(WCHL
Chapel Hill and WSOC Charlotte). I am planning to contact
them to find out what kind of response they have been
getting.(For all of you in other areas,Motorola has a list
available of stations broadcasting CQUAM).smb@ulysses.UUCP (Steven Bellovin) (02/05/84)
An industry organization has indeed picked a TV stereo standard. I don't recall any details, but they were hoping that in the face of substantial agreement the FCC would bless one single standard. Incidentally, it's been the AM broadcasters who've been clamoring for a stereo standard; they think that that's why they've lost market share to FM.... ---Steve Bellovin