Time to reconsider AM stereo?

[JohnnyElectron]

Just found a Mini-Disc I recorded of WJR on Christmas Day in 2001 playing Christmas music in stereo -and all I can say is WOW - what audio. The receiver was a Sony AM Stereo unit, and even with the 10KHz high-end filter, it still sounded FANTASTIC. I could not believe that they used to sound that good - and it was a minidisc, so I wish I had recorded direct to CD, but, the point is, wideband C-Quam stereo sounds great on a 50KW clear channel station pumping out the audio to 10KHz.
Wow, how I miss those days! Too bad they don't flip the switch back on, as they have nothing to lose!

 

[HowardMBurgers]

Indeed! Received high end 6dB down at 6 KHz. and gone around 8 Khz. Low end that rolls off completely at 80 hz. And of course don't forget the distortion figures of: 40% IMD, 15% THD.

And that stellar 10dB of stereo separation when using 125% positive modulation!

Yep, those were the good ol' days!

 

[rbrucecarter5]

Indeed! Received high end 6dB down at 6 KHz. and gone around 8 Khz. Low end that rolls off completely at 80 hz. And of course don't forget the distortion figures of: 40% IMD, 15% THD.

And that stellar 10dB of stereo separation when using 125% positive modulation!

Yep, those were the good ol' days!

Its not our fault if you bought a crummy AM receiver. I owned several C-Quam AM stereo radios and tuners, and their specs were all considerably better than the ones you described. AM is still capable of some really good fidelity, and that has been clear to crystal radio hobbyists for decades. Now that virtually all new AM radios are inherently broadband, it is time to consider a better audio chain at AM stations, not the discredited AM HD system that barely works at all and hobbles fidelity and coverage of AM stations.

 

[Savage]

Y'know, Howard, you're starting to give me the impression you don't think much of C-QUAM...

No C-QUAM AM stereo station I was ever familiar with had distortion and response like that. And: 10 dB stereo separation with 125% positive peaks? Could be. Which is precisely why the AM stereo stations that actually sounded good didn't DO 125%. ("Doctor...it HURTS when I do this." "So don't do that.")

That was the beef from programmers who didn't know any better, back when AM Stereo was trying to become accepted. They complained that the modulation density on mono receivers was gone. Those days were the closing stanza of the "loudness wars" of AM that got underway in the mid 1970s.

I would argue that the in-your-face AM audio of that era accelerated the migration of audience to FM. Basically audio quality was tossed under the bus to assuage the egos of radio managers, each of whom wanted the loudest signal on the dial. If the FCC had mandated AM Stereo and limited positive peaks to 100% eliminating asymmetry, maybe music could have stayed on AM.

Oh, yes - and IBOC wouldn't have gotten a toehold (which it is currently losing anyway.)

 

[HowardMBurgers]

Savage, I completely agree with your point that (to paraphrase), it's not the technology but how it's used. AM stereo was better than traditional AM mono, do doubt about it, but only if used within the limitations of the receiver and if consumers actually cared. Unfortunately, neither was the case.

The C-Quam and Quasi-Quam (Harris and Magnavox) receiver chips did not decode well when modulation got near 100% positive or negative and REALLY didn't work well with traditional audio processing which included a great deal of clipping or positive asymmetry. Sure when a station installed a system and did their audio proof, they had to meet specs., but that was with tones. Once the music and speech came out of the wound-up Orban 9100, DAP(s), UREI Modulimiter, or CRL boxes and hit the AM stereo exciter, all bets were off. Sure AM still sounded better, a little perhaps, but mainly just a perception of stereo image similar to reverb or delay between channels as compared to the same song played on an FM station.

Program directors weren't willing to back down in the modulation wars, combined with the potential loss of fringe area coverage that only AM could benefit from, and I believe AM stereo was doomed no matter what system would have been chosen.

My argument to the "AM stereo could save the AM band" group, is that AM stereo wasn't the panacea that some think it was. I was there testing and installing these systems. The typical end result, rather like HD on the part of broadcasters, was disappointment with the results. Sure it sounded better, but history has shown that the vast majority of listeners could care less.

 

[Savage]

I think we're largely in agreement, Howard, with a respectful dissent that goes this far: on balance, even if not particularly well-installed or maintained, AM Stereo represented a general improvement over mono. And if executed well, it sounded excellent to the average listener. There's plenty of extant proof for this. There is a YouTube aircheck of WOWO being received in Northwest PA back in the 90s, and there are other accessible examples. Just Google, find and listen.

Certainly I would argue that these airchecks demonstrate a clarity superiority and naturalness advantage over IBOC-AM, which after all is the subject of this thread. HD-AM's shrill, metallic, chorused 16 kbps primary stream is hurl-inducing. Give me a little heterodyne and adjacent-channel monkey-chatter any day over that "electronically reprocessed to resemble actual sound" Robo-Radio. (Which dumps back to analog over and over any time there is the slightest impulse noise, like somebody flipping a light switch, for example.)

Back to AM Stereo for a moment:

Oh, you were using a BL-40 Modulimiter? Hey, Howard, I just found out where your 40% IMD was coming from! Wags used to say that's what the model number stood for. The Modulimiter was a tremendously dirty box, especially on the low end. And I wouldn't use a DAP-310 unless I disabled all the diode limiting. The multiband AGC was good but the brick-wall limiter was horrible, especially with plate-mod rigs.

 

[wnmb]

"Sure it sounded better, but history has shown that the vast majority of listeners could care less." This statement is not valid, because a vast majority of listeners never got exposed to it in the first place. The combination of good receivers with AM Stereo, decent programming, and radio stations actually broadcasting in AM Stereo never got into sync. Now, would it work today? Yes. Here in North Myrtle Beach we broadcast in AM Stereo and we do it with strong engineering. The audio chain is clean. Modulation is reasonable, but we chose fidelity over loudness. The C-quam generator is better than earlier ones. The Optimod processor is kept in excellent working order and the AM Transmitter is new. Now, rather than argue about numbers, let me share with you about ears. This stuff done right in Stereo with a decent receiver is very, very good. I invite any of you to hear for yourselves. Whenever you come to the North Myrtle Beach, Grand Strand area, give me a call at 843-249-6662. I'll take you for ride in a variety of cars, all equipped with FM stereo and AM stereo on original factory radios like the Audiophile Satellite ready unit in Thunderbirds, Eddie Bauer Expeditions and Explorers. You can bounce back and forth between AM and FM until your heart is content. Make your own decision, but I bet I know what you'll say. AM stereo is very good. With a good combination of proper receivers, good engineering, and decent programming, you can compete. Now, don't take my statement as arrogant, but if we can do this here at the beach in a virtual sea of FM stations, with nobody else trying to be competitive on AM, heck, anybody can do it. I make a lot of mistakes and many of you could do better programming because I wear too many hats, but here we are at the end of 2009 with a profitable and viable AM radio station. And, yes, of course, you have to do all the other things necessary to be profitable like watching expenses and being involved in your community. Enough of this at the moment, I got to go start my Christmas shopping!

 

[davideduardo]

"Sure it sounded better, but history has shown that the vast majority of listeners could care less." This statement is not valid, because a vast majority of listeners never got exposed to it in the first place. The combination of good receivers with AM Stereo, decent programming, and radio stations actually broadcasting in AM Stereo never got into sync.

Those of us managing AM stations in larger markets in the 70's thought that AM stereo could prevent a total loss of music listening to FM. Keeping in mind that FM achieved ratings parity (half on each band) around 1977 to 1978, there was still a lot of listening to AM and a way to sell stereo to the existing listeners who were still there!

We all hoped that the final system would be approved and equipment ready for shipping by 1978. Then Leonard Kahn sued, and kept any system from seeing the light of day until about 5 years later, when AM had a decided disadvantage over FM in audience numbers, particularly for music programming.

I had signed order #1 for two of the competing systems for WQII, and would have been one of the first AM stereo stations on the air other than experimentally in any case... the studios and STL were all stereo ready.

Instead, we got what was a decent system, way too late. AM could not promote itself, as many music stations were gone, the band was becoming talk based, and the music audience had a half-decade more to decide that FM was hip and AM wasn't. Of course, it took additional time to fix the nauseating platform motion on the AM system, and there was never enough momentum to create much of a market for replacement receivers.

So, both HD and analog AM stereo were victimes of timing. In the 70's, the delay caused by the legal issues, and now, with the recession and profusion of more cool, hip devices (I want to tell you about my Logitech squeezebox internet tuner...) that make replacing a radio seem pretty much a waste.

FMs will find a market for HD niche programming, making HD the new SCA service. AM HD was an afterthought, and with the slow decay in AM listening, too little and too late.

 

[Tom Wells]

Leonard Kahn's system was better than CQUAM, but the modern world is not inclined to reward individual creativity,
preferring to reward that which is created by large corporate entities.

I say it was better because upper/lower sideband split is more robust and fully backward compatible.

I kept my eyes open to buy an AM stereo, but they never ever did appear on any shelves of stores.

If the internet had existed or some other way to locate them, I WOULD have bought one.
I asked around, but it was truly under the radar of all the marketers.
Still don't have one, but I'd be ready to modify some of my radios to achieve it.

Stereo's not one of my priorities. I listen to my music in glorious mono. I'd rather have high-quality wideband audio than stereo.

 

[RadeoEngineer]

;D Changed my mind about the post, but I thought it was funny.

 

[HowardMBurgers]

Leonard Kahn's system was better than CQUAM, but the modern world is not inclined to reward individual creativity,
preferring to reward that which is created by large corporate entities.

I say it was better because upper/lower sideband split is more robust and fully backward compatible.

I kept my eyes open to buy an AM stereo, but they never ever did appear on any shelves of stores.

If the internet had existed or some other way to locate them, I WOULD have bought one.
I asked around, but it was truly under the radar of all the marketers.
Still don't have one, but I'd be ready to modify some of my radios to achieve it.

Stereo's not one of my priorities. I listen to my music in glorious mono. I'd rather have high-quality wideband audio than stereo.

You're certainly entitled to your opinion, but as David correctly pointed out, Leonard Kahn's various filings of lawsuits was yet another nail in the coffin of AM stereo.

I remember quite well a conversation with Leonard while he was setting up a brand new test ISB AM stereo exciter at a station I worked at in 1977. The wars of words between the CQUAM camps and Leonard were heating up. While discussing it over a cup of coffee, I asked the question whether Leonard would he'd be better off just working a deal with a manufacturer such as Harris or whomever in the interest of going against Motorola, rather than taking them on as an individual. You would have thought I had just stabbed Leonard in the neck. He got really angry and defensive with even the suggestion. Clearly history has shown that Mr. Kahn was not a smart businessman.

Whereas for the time, I completely agree that Leonard was a smart inventor. The problem was all his tilting at windmills was a major reason AM stereo never got traction.

 

[rbrucecarter5]

The wars of words between the CQUAM camps and Leonard were heating up.

Whereas for the time, I completely agree that Leonard was a smart inventor. The problem was all his tilting at windmills was a major reason AM stereo never got traction.

Finally someone says it - I think Leonard Kahn and his lawsuits were a big part of the reason why AM stereo died. There was a crucial window of opportunity - before talk radio really took hold - when a concerted effort to get AM stereo mandated on all new receivers might have saved the band for music. By the time the uncertainty with formats was resolved in favor of C-Quam, it was too late. FM had continued to gain, and talk radio was entering its own.

What was needed was a concerted effort by broadcasters of the time to push the system in a united front. They learned their lesson with HD, but it is a defective system compared to C-Quam, and the window of opportunity was almost 30 years.

 

[calstymes]

Tom Wells thusly spake:

Leonard Kahn's system was better than CQUAM, but the modern world is not inclined to reward individual creativity,
preferring to reward that which is created by large corporate entities.

Now ain't that the truth?

Leonard Kahn is the whipping boy that everyone just loves to bash and on whom everyone blames all of AM radio's current ills and woes because of his law suit. Well I guess someone has to be a target so it might as well be him, yes? Never mind whether or not the suit and his engineering had merit.

Now that is what iBiquity's arguments were when it was challenged by the boys who ended up putting their marbles into FMeXtra, eh? A simple buyout to suppress sufficed then. Why couldn't Motorola have thought of that when Kahn was making engineering sense? Then the issue (and his suit) might never have occurred, the FCC would have approved CQUAM, Leonard would not have become the industry's whipping boy and we would have had the kind of garbage with AM stereo that we have today with HD Radio, but perhaps not quite as bad.

But back to Tom's original comment, how about getting some decent and advanced engineering smarts at the FCC and cut out the political crap which only serves to reinforce the continued big corporate manipulation of the marketplace? It is not as if the problems with IBOC could not have been predicted by physics, yet the FCC keeps approving iBiquity's requests.

Awful? Yes. Astonishing? Not in today's world. Very very sad.

 

[Play Freebird]

Whereas for the time, I completely agree that Leonard was a smart inventor. The problem was all his tilting at windmills was a major reason AM stereo never got traction.

I'm sure a major part of the problem was Leonard's frustration with the FCC. The application for his first AM stereo patent was actually filed back in February 1960 and he tried to gain regulatory approval shortly thereafter, but the FCC refused to act on his request for nearly 20 years. As usual, the big companies like Motorola, Harris, Philips, and RCA jumped in with their competing systems, and through their money and political influence were successful in getting the Commission's attention.

Mexico approved Kahn's system much earlier, it was on the air at XETRA 690 in the '60s.

Here's the link to Kahn's informative 1960 patent document:
http://www.google.com/patents/about?id=6jphAAAAEBAJ&dq=3218393

 

[HowardMBurgers]

Why couldn't Motorola have thought of that when Kahn was making engineering sense? Then the issue (and his suit) might never have occurred, the FCC would have approved CQUAM, Leonard would not have become the industry's whipping boy and we would have had the kind of garbage with AM stereo that we have today with HD Radio, but perhaps not quite as bad.

Leonard did it to himself. Coming off as an annoying crackpot by filing pointless lawsuits, combined with not acting in a business-like manner whenever he was asked an opinion, ruined whatever credibility he had to the FCC and the other manufacturers. In the end all that happenned was he became part of sabotaging AM stereo as a whole and his lawyer probably bought a new nice boat.

But back to Tom's original comment, how about getting some decent and advanced engineering smarts at the FCC and cut out the political crap which only serves to reinforce the continued big corporate manipulation of the marketplace?

Yeah, good luck with that. The FCC has few qualified engineers anymore. They rely on the private sector to tell the politicans what works and what doesn't.

 

[davideduardo]

[Mexico approved Kahn's system much earlier, it was on the air at XETRA 690 in the '60s.

Mexico did not approve the system. They approved experimental transmission limited to that one station. As many who heard it recall, the separation was only slightly better than that of the "put your AM radio to the left of you and your FM to the right" experiments (or gimmicks) of the period.

Similarly, Mexico has approved on a temporary basis the use of HD by Mexican stations on the US border. Since Mexico is in the process of trying to move all AMs off the band, this would principally affect FM broadcasters in the long run.

 

[landtuna]

As many who heard it recall, the separation was only slightly better than that of the "put your AM radio to the left of you and your FM to the right" experiments (or gimmicks) of the period.

I don't recall using any FM's but do remember an experiment on KTKT and, I believe, KAIR (both mono AM's) of the late 50's where they broadcast one channel on each station. I remember listening to it but not really impressed.

 

[badjef]

Leonard Kahn's system was better than CQUAM, but the modern world is not inclined to reward individual creativity,
preferring to reward that which is created by large corporate entities.
I say it was better because upper/lower sideband split is more robust and fully backward compatible.
I kept my eyes open to buy an AM stereo, but they never ever did appear on any shelves of stores.
If the internet had existed or some other way to locate them, I WOULD have bought one.
I asked around, but it was truly under the radar of all the marketers.
Still don't have one, but I'd be ready to modify some of my radios to achieve it.

Stereo's not one of my priorities. I listen to my music in glorious mono. I'd rather have high-quality wideband audio than stereo.

Merry Christmas! Happy to find another Kahn supporter. It was available as an "add-on" which is how I was able to record it in my '87 Toyota. The Sony STF-A100 was the only receiver with the decoding built in and it was pulled off the market with a Candygram from Motorola to "cease and desist" any manufacturing of AM Stereo radios other than c-Quam.

That was your "marketplace decision."

Jeff in Sa-ra-so-ta!

 

[calstymes]

HowardMBurgers reiterated:

Quote from: Cal Stymes on December 24, 2009, 10:12:58 AM:

Why couldn't Motorola have thought of that when Kahn was making engineering sense? Then the issue (and his suit) might never have occurred, the FCC would have approved CQUAM, Leonard would not have become the industry's whipping boy and we would have had the kind of garbage with AM stereo that we have today with HD Radio, but perhaps not quite as bad.

Leonard did it to himself. Coming off as an annoying crackpot by filing pointless lawsuits, combined with not acting in a business-like manner whenever he was asked an opinion, ruined whatever credibility he had to the FCC and the other manufacturers. In the end all that happened was he became part of sabotaging AM stereo as a whole and his lawyer probably bought a new nice boat.

But my point is, Mr. Kahn keeps getting blamed for starting the "death" of AM. To this day we raise his name in vain, and for what purpose? How does this help us eliminate the adjacent channel AM interference being caused by IBOC? The man was clearly brilliant and the world wasn't ready for him. He also had absolutely nothing to do with the invention of IBOC. It was and is not his fault that the modern world is not inclined to reward individual creativity, then or now.

Quote from: Cal Stymes on December 24, 2009, 10:12:58 AM:

But back to Tom's original comment, how about getting some decent and advanced engineering smarts at the FCC and cut out the political crap which only serves to reinforce the continued big corporate manipulation of the marketplace?

Yeah, good luck with that. The FCC has few qualified engineers anymore. They rely on the private sector to tell the politicans what works and what doesn't.

I am suggesting that our federal regulatory agencies should act more responsibly. You are saying that is not going to happen and I already know that. My (and Tom's) underlying point is that it's horrible the broadcast industry is being regulated by a federal agency that no longer understands the science of what it is regulating and that corporate greed most always gets the nod.

It's as simple as that. The FCC is no longer functioning in the public interest and while this only represents a microcosm of what is happening in our society as a whole, it is still a very BIG problem.

 

[TheBigA]

My (and Tom's) underlying point is that it's horrible the broadcast industry is being regulated by a federal agency that no longer understands the science of what it is regulating and that corporate greed most always gets the nod.

No one gives them a nod. The difference is that in the vacuum that exists in broadcast regulation, radio companies simply do what they want. They don't need permission. They are licensees. If I have a license to drive, I don't need to ask the DMV permission every time I get in the car.

As for the FCC operating in the public interest, we've had more than 16 years where the general feeling was the government that governs least governs best. That is the public interest as defined by the voters. Any time the government attempts to take action, it gets mired in political agendas. The FCC has been unable to get any kind of consensus on anything related to broadcasting, except with regards to indecency. Couple that with 25 years of budget cuts, and you end up with our current situation.