AM Stereo

[kenglish]

Guess the question is: why?

Guess someone should call and ask them.

 

[Kelly A]

Won't be me. I could care less about an old piece of gear that was half-baked when it was new forty years ago, let alone the motivation for someone using it on the air.

 

[kenglish]

I would think you'd share your knowledge for the good of all broadcasters. It's just a phone call.

 

[dumber than a box of hair]

Actually all of the systems are still legal to use, just as long as they are not transmitting stereo audio.

Incorrect...use of any stereo system,including the pilot, but even with mono audio,is illegal.

One can still broadcast in Motorola CQUAM AM stereo, but the audio must be stereo.

Try reading the rules: Electronic Code of Federal Regulations (eCFR)

AM stereo is still permitted, but there is no specific requirement that the audio actually be stereo. Sub (c) of 73.128 effectively permits only the C-QUAM system by specifying that system’s mathematical models.

 

[Kelly A]

I would think you'd share your knowledge for the good of all broadcasters. It's just a phone call.

The way it works is: They request my services, and pay for my advice. No pay, no play.

 

[Kelly A]

Try reading the rules: Electronic Code of Federal Regulations (eCFR)

AM stereo is still permitted, but there is no specific requirement that the audio actually be stereo. Sub (c) of 73.128 effectively permits only the C-QUAM system by specifying that system’s mathematical models.

I never said AM stereo wasn't permitted. I said Motorola was the only AM stereo system allowed, and that you couldn't run a stereo pilot without broadcasting stereo audio. Same goes for FM stereo.
Stations can't run Kahn ISB or Magnavox AM stereo anymore. Those aren't type approved.

 

[kenglish]

What is the issue with stereo-or-not? Is it something to do with noise levels or something? Is it just a case of the stereo light being "false advertising"?
I'm confused.

 

[Kelly A]

What is the issue with stereo-or-not? Is it something to do with noise levels or something? Is it just a case of the stereo light being "false advertising"?
I'm confused.

It's an old leftover rule from back when FM stereo was first allowed. If you aren't running stereo audio, the Commission felt you shouldn't be broadcasting a stereo pilot. Back in the beginning, some stations would turn off their pilot during newscasts, then back on when music played. I remember having an argument with a station manager about this. The look on his face when I said that technically, each time a jock opens the mic the station should be dropping the pilot. His solution? Install two microphones, one left and one right. Of course, I doubt anyone ever got busted for this particular rule anyway.

 

[dumber than a box of hair]

I never said AM stereo wasn't permitted.

No, ContinuousWave said that.

I said...you couldn't run a stereo pilot without broadcasting stereo audio. Same goes for FM stereo.

Incorrect. The requirement to drop the pilot on FM in the absence of stereo audio was dropped many years ago. See sections 73.297 and 73.322 of the FCC rules. As for AM, I don’t see anything in 73.128 which mandates dropping the pilot on AM when there’s no stereo audio present.

 

[Theater of My Mind]

I never said AM stereo wasn't permitted. I said Motorola was the only AM stereo system allowed, and that you couldn't run a stereo pilot without broadcasting stereo audio.

Back in the day, didn't some AM stations run a stereo pilot without broadcasting stereo audio because it caused certain car radios to switch to wideband mode and sound better/louder than their regular AM competitors?

 

[Kelly A]

Back in the day, didn't some AM stations run a stereo pilot without broadcasting stereo audio because it caused certain car radios to switch to wideband mode and sound better/louder than their regular AM competitors?

There may have been, none that I ever dealt with. Years ago I had a 1998 Grand Cherokee with an AM stereo-capable tuner from the factory. Sometimes at night when tuning around to a distant station, or on the fringe, it would kick into AM stereo mode. The station would definately sound wider, even though it wasn't actually stereo. The hetrodyne caused by co-channel stations beating against each other, created a low frequency product that made the the radio think there was a stereo pilot present.

 

[badjef]

Yep, technically same goes with FM stereo. If you broadcast mono audio, you're supposed to turn off the pilot.

One can still broadcast in Motorola CQUAM AM stereo, but the audio must be stereo. The other systems, including Kahn and Magnavox, were tested under a special STA back in the day. Stations can no longer use those systems on the air without filing, and getting approval, for an STA to test a system on the air. Not that there would ever be a reason to....

One of the WORST requirements of the FCC of all time!

Turn on the pilot or turn off the pilot depending on the information is STUPID!!!

Every stereo radio station in the country would still be operating illegally since the studio microphones are MONO.

It certainly didn't work in the 60's when (I was reminded) the early FM Stereo receivers would mute the audio when there was no pilot. If the station was playing a mono recorded record, it wasn't heard over the air by those radios which were muted.

Reality: Even with mono information, there is still a spatial effect with the pilot.

And, that makes stereo, special.
(yup, I went there)

Jeff in Sa-ra-so-ta!

 

[RadioFan2J3]

One of the WORST requirements of the FCC of all time!

Turn on the pilot or turn off the pilot depending on the information is STUPID!!!

Did any station turn off the stereo pilot based on the specific content within a program?

Every stereo radio station in the country would still be operating illegally since the studio microphones are MONO.

As Kelly noted, just put two mikes in the control room and then even the announcer is in stereo. I knew of one station in a small market in Georgia, per their engineer, that he did that for the CR mikes.

It certainly didn't work in the 60's when (I was reminded) the early FM Stereo receivers would mute the audio when there was no pilot. If the station was playing a mono recorded record, it wasn't heard over the air by those radios which were muted.

Back to my above question, how many stations did cut the pilot for a mono record? None, probably.

Back in those days, I was working at one station which was beautiful music on the FM, automation system, all the music tapes were stereo. None of the carted material was stereo, and we certainly did not cut the pilot for those mono segments.

But we did run Atlanta Falcons football on the FM and per policy of the time, we did cut the stereo pilot, well, if anyone thought to do it. I remember on series of calls from a listener who complained that he would lose audio on our programming for hours at a time. I never had a receiver that would mute when the stereo pilot was missing, so I did not immediately connect that with the listener's program, but once time he called, telling me about the problem, I was in the building and I asked him if he was listening to us, yes, tell me if the audio disappears (I had gone to the stereo generator and turned off the pilot), yes, audio muted, and I turned the pilot back on, audio unmuted.

I explained the situation and once he understood that when the audio was muted, it was a football game (more technically, a longer mono program which was not the music he wanted to hear), he was satisfied and issue was solved.

 

[frankberry]

In the early days of FM stereo, many stations had their announce microphones on one channel only. That made it "technically" legal.

 

[ncradioeng]

The Heathkit AR-15 receiver has a norm / stereo only switch.

 

[Kelly A]

Obviously it doesn't matter anymore because this rule was done away with, but even back then, the semantics were that if the station had both left and right channels being fed, even a mono source, it was still considered stereo. Some argued that since the source was mono, the audio was mono. I argued that as long as both channels contained audio, the station was technically "broadcasting" stereo. .

I do recall some stations in the heat of loudness wars back in the 70's, running mono audio but injecting a 19kHz pilot tone to turn the stereo light on receivers-on. This eliminates the 38 and 53khz subcarriers. By eliminating all the subcarriers except the pilot, stations were louder and appeared to suffer from less multipath. In this example, I DO know a couple stations who got caught doing this.

 

[semoochie]

Did any station turn off the stereo pilot based on the specific content within a program?



As Kelly noted, just put two mikes in the control room and then even the announcer is in stereo. I knew of one station in a small market in Georgia, per their engineer, that he did that for the CR mikes.





Back to my above question, how many stations did cut the pilot for a mono record? None, probably.

Back in those days, I was working at one station which was beautiful music on the FM, automation system, all the music tapes were stereo. None of the carted material was stereo, and we certainly did not cut the pilot for those mono segments.

But we did run Atlanta Falcons football on the FM and per policy of the time, we did cut the stereo pilot, well, if anyone thought to do it. I remember on series of calls from a listener who complained that he would lose audio on our programming for hours at a time. I never had a receiver that would mute when the stereo pilot was missing, so I did not immediately connect that with the listener's program, but once time he called, telling me about the problem, I was in the building and I asked him if he was listening to us, yes, tell me if the audio disappears (I had gone to the stereo generator and turned off the pilot), yes, audio muted, and I turned the pilot back on, audio unmuted.

I explained the situation and once he understood that when the audio was muted, it was a football game (more technically, a longer mono program which was not the music he wanted to hear), he was satisfied and issue was solved.

You made me think of something that probably hadn't occurred to me since 1974! When I was babysitting the Beautiful Music FM, on Sunday morning at six, it went into a simulcast with the AM Country station and I vaguely remember turning off the stereo pilot.

 

[davideduardo]

In the early days of FM stereo, many stations had their announce microphones on one channel only. That made it "technically" legal.

You will be amused by an early FM stereo story: After my first independent FM in Ecuador was on for about a year, I wanted to "go stereo" but it was not billing anything yet. So I worked with a friend, the CE at Philips Ecuador, to take a test bench unit that generated a stereo simulation. We stabilized the unit a bit and added an audio input circuit to what was a test only circuit and then matched it to out home brewed transmitter. While the specs may have been a bit less spectacular than a true stereo exciter from Gates or Collins at the time, it sure sounded nice when we were the only independent FM on the band, and the only other stations were my AM simulcasts.

Those are things you do when the top of the market spot rate was about $1.

 

[ContinuousWave]

No, ContinuousWave said that.

Incorrect. The requirement to drop the pilot on FM in the absence of stereo audio was dropped many years ago. See sections 73.297 and 73.322 of the FCC rules. As for AM, I don’t see anything in 73.128 which mandates dropping the pilot on AM when there’s no stereo audio present.

I never said AM stereo wasn't permitted..hell, I put on the only AM stereo in the state of LA back in May 2020 and owned an AM stereo music station in TX from 2015 to Dec 2019

 

[tvnut]

You will be amused by an early FM stereo story: After my first independent FM in Ecuador was on for about a year, I wanted to "go stereo" but it was not billing anything yet. So I worked with a friend, the CE at Philips Ecuador, to take a test bench unit that generated a stereo simulation. We stabilized the unit a bit and added an audio input circuit to what was a test only circuit and then matched it to out home brewed transmitter. While the specs may have been a bit less spectacular than a true stereo exciter from Gates or Collins at the time, it sure sounded nice when we were the only independent FM on the band, and the only other stations were my AM simulcasts.

Those are things you do when the top of the market spot rate was about $1.

You have to write a book. Count me as buyer No. 1.