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AM Stereo

I still have my Radio Shack AM stereo tuner. Here in the Atlanta area WSB used to transmit AM stereo in the late '80's before they became all talk.

They stopped using the mode, according to the Chief Engineer at the time, who told me that the then new General Manager was concerned that the stereo signal was reducing the signal coverage.
 
The GM has his head stuck somewhere cold and dark...
No, he was probably right. At least the perception to the audience, was that the coverage improved. Have witnessed it several times. Usually the difference comes depending on how the AM stereo exciter interfaced with whatever model of transmitter. Back in the day, nobody offered AM stereo as an option in a transmitter, so interfacing an external exciter was usually a compromise.
 
Meanwhile the web receiver KiwiSDR has just enabled AM stereo on its system!

I'm listening to WIOE, 1450 kHz, Fort Wayne, IN (oldies) in stereo via a KiwiSDR in Elida, OH, as I type this! Very neat.
 
No, he was probably right. At least the perception to the audience, was that the coverage improved. Have witnessed it several times. Usually the difference comes depending on how the AM stereo exciter interfaced with whatever model of transmitter. Back in the day, nobody offered AM stereo as an option in a transmitter, so interfacing an external exciter was usually a compromise.
Total BS....there is NO LOSS of coverage running stereo AM...the GM did have his head somewhere cold and dark. His ass
 
Meanwhile the web receiver KiwiSDR has just enabled AM stereo on its system!

I'm listening to WIOE, 1450 kHz, Fort Wayne, IN (oldies) in stereo via a KiwiSDR in Elida, OH, as I type this! Very neat.
WION 1430 streams off their Carver AM stereo rcvr...sounds great...Greg Buchwald, who was on the Motorola Cquam team, has made mods to their Optimod processor over the years to improve the sound
 
Perceived loss of coverage is not the same as actual loss of coverage. There is no reason in the world why AM stereo would decrease the station's coverage area.
Agree, but listeners perception of a loss of coverage is what matters. It's a lot like what we're facing today with so much increase in terrestrial interference from noisy consumer electronic devices and aging utility infrastructure. An AM station may be maintaining licensed parameters and field strength, yet listeners can't receive the station very well, if at all. Ultimately who's held responsible?

Back in the early 90's the GM of a station where I took over as Chief was complaining that it didn't seem like the station covered as well as it used to. After running a skeletal proof and determining the field strength was at licensed parameters, I repaired the backup transmitter, then put it on the air. Immediately calls poured into the front desk and control room wondering what we did, because they could receive the station so much better. Next step was to pull the Motorola CQUAM exciter out of the main transmitter and reconnect the factory exciter. (Collins 828 E-1 5kW Power Rock) Complementary calls from listeners continued for several days and the GM was very happy.
 
An AM station may be maintaining licensed parameters and field strength, yet listeners can't receive the station very well, if at all.
Over the last few years there has been more noise on the AM band but not as much as to completely ruin reception. Driving around the metro Atlanta suburbs the reception on my car radio continues to be pretty much the same as it was 30 years earlier.

The only thing that has changed is that talk radio programming has driven listeners away. The younger generation is listening to streamed audio via their cell phones not because of noise on the AM band.

I have never heard anyone actually and directly complain to me that they don't listen to the radio because of noise.
 
A Cquam station would have problems on a radio with a diode detector. That's because Cquam uses TWO carriers (90 degrees out of phase). When those two carriers are detected by a diode detector the resultant is algebraically summed and the result is .707 times that of a single carrier (a loss).
PLL radios overcome problem by tracking the input wave. Another term for this is synchronous detection. Obviously, diode detection is asynchronous.
Most digitally tuned radios are PLL. Analog tuned radios are most likely diode detection.
Cquam is nothing new. This method of transmitting information has been used in transmitting NTSC color since 1954 (or thereabouts).
 
A Cquam station would have problems on a radio with a diode detector. That's because Cquam uses TWO carriers (90 degrees out of phase). When those two carriers are detected by a diode detector the resultant is algebraically summed and the result is .707 times that of a single carrier (a loss).
PLL radios overcome problem by tracking the input wave. Another term for this is synchronous detection. Obviously, diode detection is asynchronous.
Most digitally tuned radios are PLL. Analog tuned radios are most likely diode detection.
Cquam is nothing new. This method of transmitting information has been used in transmitting NTSC color since 1954 (or thereabouts).
You make a good point. The 80's and early 90's was a transitional period for AM receivers too. Listeners didn't/don't know the difference of what type of radio they're listening to. They just know what they hear.

The station was losing listeners due to something that hardly anyone at the time could even appreciate. That's just bad for business.
 
A Cquam station would have problems on a radio with a diode detector. That's because Cquam uses TWO carriers (90 degrees out of phase). When those two carriers are detected by a diode detector the resultant is algebraically summed and the result is .707 times that of a single carrier (a loss).
PLL radios overcome problem by tracking the input wave. Another term for this is synchronous detection. Obviously, diode detection is asynchronous.
Most digitally tuned radios are PLL. Analog tuned radios are most likely diode detection.
Cquam is nothing new. This method of transmitting information has been used in transmitting NTSC color since 1954 (or thereabouts).
Your statement is true for Quam...Cquam is Compatible...the C in Cquam...it is totally compatible with envelope detectors...NTSC color is NOT Cquam. It is totally different..there is no phase mod involved in NTSC.
 
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