History about broadcast AM/FM stereo in the USA? |Radiomuseum.org

History about broadcast AM/FM stereo in the USA?

12.Oct.07 10:07

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Juha Lahtinen Liljeroos (FIN)
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Dear All

I have one tube stereo radio (one canal am other fm) Packard & Bell I think that it is made late 1950.

Now I would like to ask what is history for stereo radio broadcast in the USA ?.

Many Thanks

Best Regards Juha

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AM_FM for two channel Stereo without MPX

12.Oct.07 22:20

Hans M. Knoll (D)
Editor
Articles: 2165
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Hello Juha,

please read this website from USA,

there you can find all about Tuners for AM and FM with and without MPX Stereo

Regards, hans m. knoll

http://www.fmtunerinfo.com/amtuners.html

example from there:

The golden age of AM tuners. Stereo was first available to consumers around 1955, as two-track 7½" reel tapes. The stereo record was released in 1958. It wasn't until June of 1961 that the FCC final approved the Zenith approach to FM multiplex. In the meantime, the FCC allowed broadcasters to fill the void via AM/FM stereo simulcasts. Odd as it seems, the right channel was sent out on an FM channel and the left channel was sent out on AM. You may wonder about the matching of channels and the quality of imaging made in this way, but remember that this was in the very early days of stereo when it wasn't all that unusual to convert to stereo by picking up a second speaker that wasn't even of the same brand as your first speaker. ("Sound from the left and sound from the right - that's stereo!") I don't know how prevalent these broadcasts were, but evidently they were common enough that a number of tuner manufacturers built tuners to cater to them. They are easy to spot in that they are really two independent tuners on one chassis. Look for two tuning knobs, two dial pointers, and complex mode switching for FM, AM and AM/FM

stereo.

The benefit here is not that any AM/FM simulcasts exist today but that, for these simulcasts, the manufacturers gave their best shot to making AM sections approach the sound quality of their FM sections. I won't say that they would fool you into believing that they were FM, but during daytime hours and using the widest bandwidths the AM sections did come passably close to FM quality. Typical specs and performance would be a frequency response of 20 to 8000 Hz (or wider with whistle filtering bypassed), with 0.5% distortion and a signal-to-noise ratio of about 45 to 50 dB. Most of these tuners come from the 1958-to-1961 era and include such notable sets as the Fisher 800C receiver, the McIntosh MR 66, the Scott 330 and 331, and several Heathkit and Sherwood models. Other sets from just before or just after this period had similar AM section properties, but without the fully independent tuner sections. For our purposes these would be equally desirable and would include the Mac MR 55, and the Fisher AM80 and FM90T variations. In fact, just about any AM/FM tuner from this era with 3-gang tuning and at least two positions of AM bandwidth is worth a try, and likely to give better AM performance than a lot of modern sets.

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AM_FM for two channel Stereo without MPX

15.Oct.07 14:00

Juha Lahtinen Liljeroos (FIN)
Articles: 23
Count of Thanks: 7

Many Thanks Hans

It was Great to get feedback and read some near history (already 50 years old).

Many Thanks

Juha

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Tanks

15.Oct.07 15:32

Hans M. Knoll (D)
Editor
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Count of Thanks: 5

Hello Juha,

I am glad its help you.

Hans

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A good article which covers the history of stereo reception

08.Jun.09 08:48

Ernst Erb (CH)
Officer
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After reading the few sentences below, I looked out for a good article for Radiomuseum.org and fell on this one only.

Is there anybody out there who could work out a full history on this subject?

1945:
"KFAC, LA's then all-classical station, had recently begun broadcasting in FM, as well as AM. Then one day they proudly announced that they were going to be playing a two-hour concert in stereophonic sound. But in order to enjoy this amazing event you would need two radios—one AM and one FM.

So Carl and I, full of anticipation, set up his old AM radio and my recently acquired Zenith AM/FM on either side of his room and anxiously awaited the very first Southern California Gas Co. Evening Concert in Stereo. To us this was a really big event."

I can imagine that this was not the first such event worldwide - but who knows more and can tell us what steps followed etc.?

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KFAC and Stereo Transmission

10.Jun.09 08:18

Omer Suleimanagich (USA)
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KFAC was an amazing radio station until Louise Heifetz (daughter-in-law of the violin virtuoso Jascha Heifetz) purchased the station in 1986. With poor management and an avarus desire to make a lot of money, she sold the station with other investors, for over $50,000,000 in 1989 and the music format changed to Hip Hop, thus killing a Los Angeles cultural pillar overnight!

As for "stereo" broadcasts in Los Angeles, it kind of started with live broadcasts from the Hollywood Bowl in 1952, when one microphone on one side was connected to the AM transmitter and the other microphone was connected to the FM transmitter. If memory serves me correct, the radio station was allowed to do this, after its listeners petitioned the Federal Communications Commission to allow simultaneous AM and FM radio transmisions of the same program material, since this was not permitted by FCC rules.

From KFACs inception, to its end, it contained the largest classical music collection west of the Mississippi , had excellent announcers,excellent programming, and brought live NY Met Opera.

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Arvin Stereo with AM & FM

11.Jun.09 14:18

Joe Sousa (USA)
Editor
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Thank you all for the very interesting info.

One example of a radio that was made to receive Stereo broadcasts that were sent with one channel via FM and the other channel via AM, is the ARVIN 3586 with the second channel companion unit ARVIN 1586

The first unit contained independent AM and FM tuners, and the second unit was the optional second audio power amplifer and speaker. The two unit arrangement made it possible to sell the main as a mono AM-FM radio, as well as the master unit for a stereo arrangement.

About AM-Stereo: The last AM-stereo station broadcasting in the Boston Massachusetts USA area, WJIB, changed to mono when their Stereo transmitter was destroyed by a power surge that was caused by electrical repairs by the power company. I got this info from Bob Bittner, the owner of the station. As far as I know there are no more AM-stereo broadcasts in New England USA.

Regards,

-Joe

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AM Stereo technical background

13.Jun.09 10:57

Dietmar Rudolph † 6.1.22 (D)
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Some technical background about AM and AM Stereo can be found in German here.

Can anybody assist (and correct) a translation of the .pdf text? Any help will be appreciated.

Regards,

Dietmar

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