Back to analog stereo AM?

[RadeoEngineer]

Satech I did my own Kahn installation. He never even suggested he be involved unless I needed help, then he would take my calls and help that way. It was a very easy installation but I did call him to make sure I was getting a couple of things right. I also had a magnificent Sony boombox (don't remember the model #) that I used to listen. It also decoded all four competing systems. The Kahn system worked well and sounded great. I also did a couple of C-quam installs, and they worked well and sounded great as well. I would agree that Leonard was his own worst enemy, but he was very passionate about his system.

 

[KB1OKL]

And all of this just underscores how AM IBOC, even with only one system to deal with, is not a viable solution, and even with a huge marketing effort and fair amount of receivers on the marketplace, is a failure which even of its most diehard supporters are slowly abandoning.

But there is a huge difference, AM stereo worked and worked well, AM IBOC?

 

[badjef]

And all of this just underscores how AM IBOC, even with only one system to deal with, is not a viable solution, and even with a huge marketing effort and fair amount of receivers on the marketplace, is a failure which even of its most diehard supporters are slowly abandoning.

But there is a huge difference, AM stereo worked and worked well, AM IBOC?

Not only that, but it worked in the real world of motor vehicles. Iboc doesn't work well past a certain distance and requires "baby sitting". All the systems limited range except ISB. You effectively had the same range in both stereo and mono - and it wasn't as complicated.

Jeff in Sa-ra-so-ta!

 

[Tom Wells]

And Kahn's system works ALONG WITH the laws of nature, which is why its range was equal to mono, and
why its stereo did not degrade. He wasn't asking the waveform make any "special" loop-do-loops to get
a difference signal. There's already a proper "place" for such separate information to exist without any interference.
He figured out the most forthright and direct way to use the separate sidebands.

If we're not going to have the best possible system, then I really don't need AM stereo.

CQUAM was interesting, but I never owned any AM stereo radio. Only ever heard it in rental cars.

 

[KB1OKL]

And all of this just underscores how AM IBOC, even with only one system to deal with, is not a viable solution, and even with a huge marketing effort and fair amount of receivers on the marketplace, is a failure which even of its most diehard supporters are slowly abandoning.

But there is a huge difference, AM stereo worked and worked well, AM IBOC?

Incidentally Satech, if you thought my response was a little strange, it's because I misread your post, I thought you said that IBOC IS a viable solution.

 

[N1WVQ]

Again, 6kc. of audio with Kahn-Hazeltine vs. 10kc.+ with C-QuAM? Interference to one channel? No thanks. I'm glad C-QuAM is our system. Magnavox's sounded even better but Lenny's little tantrum robbed us all of that. David Eduardo's right: Kahn's lawsuit couldn't have come at a worse time. Now, less than 100 stations in this country are using A.M. Stereo & fewer are playing music. Hey, THAT'S some legacy! If he hadn't had his little tantrum at least A.M. Stereo would've had a fighting chance.

We did use Powerside at WPEP incidentally. But, since it was 2003-5, its "benefits" were lost on modern radios; you know, the ones that CAN'T tune a little above or below the carrier because they're digitally tuned! Again, what advantage would ISB have had today with digitally tuned radios (mono only) when the overwhelming majority of them only tune in 10kc. steps? None. So much for getting 2 radios & tuning them slightly above & below. That's a Rube Goldberg solution if there ever was one...well, almost as bad as IBOC.

But hey, F.M. was destined to overtake A.M. anyway especially now with all the noisemakers that spew out garbage over swaths of frequencies. Light dimmers, computer monitors, steel buildings acting as Faraday cages & my personal fave: whatever those boxes on phone poles are (Fios?). As for coverage, that's lost today too. David, what's the minimum "listenable" A.M. signal level in L.A.? 10-15mV/m? I know I saw you post it on the L.A. board before.

Let's face it: mediumwave is a lot like a mill town: it was a great place to be in the 1920s but is now just a run-down ghetto. :-[ Do I blame Kahn entirely for today's A.M. radio problems? No, of course not. Looking back, it seems inevitable F.M. would take over (it too has its share of interference problems with "non-intentional" radiators) but also looking back, it seems some A.M. operations just threw up their hands & gave up. But, it's too bad C-QuAM wasn't chosen sooner. 1985 in Australia; 1993 in the U.S.. Plus, from what I understand, the platform motion problems were solved in later chipsets.

One poster asked something along the lines of why weren't A.M. & T.V. stereo decided in 1961 when F.M. was given the green light? Well, from my understanding, Kahn & RCA-Belar had systems ready to go. But as F.M. was languishing, they wanted to give F.M. a competitive advantage. Thankfully, this allowed A.M. & T.V. stereo technologies to develop a further 15-20 years. T.V. got stereo in 1984, A.M. in 1979 (approved 1982, standardized 1993).

My next question: why can I get a stereo T.V. no problem but not A.M. stereo?! :-\

 

[badjef]

Let's see, where should I start? ELP:"From the Beginning.

Again, 6kc. of audio with Kahn-Hazeltine vs. 10kc.+ with C-QuAM? Interference to one channel? No thanks. I'm glad C-QuAM is our system. Magnavox's sounded even better but Lenny's little tantrum robbed us all of that. David Eduardo's right: Kahn's lawsuit couldn't have come at a worse time. Now, less than 100 stations in this country are using A.M. Stereo & fewer are playing music. Hey, THAT'S some legacy! If he hadn't had his little tantrum at least A.M. Stereo would've had a fighting chance.

We did use Powerside at WPEP incidentally. But, since it was 2003-5, its "benefits" were lost on modern radios; you know, the ones that CAN'T tune a little above or below the carrier because they're digitally tuned! Again, what advantage would ISB have had today with digitally tuned radios (mono only) when the overwhelming majority of them only tune in 10kc. steps? None. So much for getting 2 radios & tuning them slightly above & below. That's a Rube Goldberg solution if there ever was one...well, almost as bad as IBOC.

But hey, F.M. was destined to overtake A.M. anyway especially now with all the noisemakers that spew out garbage over swaths of frequencies. Light dimmers, computer monitors, steel buildings acting as Faraday cages & my personal fave: whatever those boxes on phone poles are (Fios?). As for coverage, that's lost today too. David, what's the minimum "listenable" A.M. signal level in L.A.? 10-15mV/m? I know I saw you post it on the L.A. board before.

Let's face it: mediumwave is a lot like a mill town: it was a great place to be in the 1920s but is now just a run-down ghetto. :-[ Do I blame Kahn entirely for today's A.M. radio problems? No, of course not. Looking back, it seems inevitable F.M. would take over (it too has its share of interference problems with "non-intentional" radiators) but also looking back, it seems some A.M. operations just threw up their hands & gave up. But, it's too bad C-QuAM wasn't chosen sooner. 1985 in Australia; 1993 in the U.S.. Plus, from what I understand, the platform motion problems were solved in later chipsets.

One poster asked something along the lines of why weren't A.M. & T.V. stereo decided in 1961 when F.M. was given the green light? Well, from my understanding, Kahn & RCA-Belar had systems ready to go. But as F.M. was languishing, they wanted to give F.M. a competitive advantage. Thankfully, this allowed A.M. & T.V. stereo technologies to develop a further 15-20 years. T.V. got stereo in 1984, A.M. in 1979 (approved 1982, standardized 1993).

My next question: why can I get a stereo T.V. no problem but not A.M. stereo?! :-\

 

[tomservo]

My next question: why can I get a stereo T.V. no problem but not A.M. stereo?! :-\

Are you talking about today, or in general?

Today with all TVs having ATSC tuners, stereo sound is just part of the data stream. I haven't seen a TV yet that didn't have stereo sound and a digital tuner. Or for that matter, a TV that doesn't include a way to access the multiple audio tracks that may be present.

Going back to analog days, however, there were still a lot of mono sets for sale before the switchover. MTS stereo was far from ubiquitous. When I lived in Mississippi, not a single commercial station near me ran stereo, including some of the ones down in Jackson. Only the PBS relays did, some of which also featured SAP if I remember correctly. In big markets like Memphis and Birmingham stereo was present on all the commercial stations, PBS and even some translators/LPTVs, and SAP was present on several channels but often unused.

I guess the reasons that television stereo became more widespread is that MTS was standardized from the get go in 1984 after testing, and the rise in home theater technology, with surround sound and hi-fi VHS tape decks helping to make movie watching better.

 

[satech]

And Kahn's system works ALONG WITH the laws of nature, which is why its range was equal to mono, and
why its stereo did not degrade. He wasn't asking the waveform make any "special" loop-do-loops to get
a difference signal. There's already a proper "place" for such separate information to exist without any interference.
He figured out the most forthright and direct way to use the separate sidebands.

Actually, only Kahn's older 1977 exciter design (STR-77) produced "real" independent sideband, through a series of complex filters, that were extremely difficult to re-tune to a different operating frequency once the exciter was built. The later 1984 design (STR-84), which most Kahn AM Stereo and Power-Side stations used on the air, produced phase modulation, except with additional phase shifts to the L+R and L-R components, to effectively place the L and R channels on the lower and upper sidebands. In fact, if you take away the phase shifts, the STR-84 produces a signal virtually identical to Magnavox's system.

Speaking of which, I wonder how many stations are still using Kahn Power-Side? In NYC there were two up until a few years ago: 1280 WADO and 1600 WWRL, but then WADO switched to IBOC, and I think WWRL turned their Power-Side off.

 

[N1WVQ]

To which sideband did WADO throw more power? I imagine WWRL threw more to the upper. Is this correct?

 

[N1WVQ]

There is 1 station (well, 2 kinda) using Kahn-Hazeltine ISB stereo. It's a Part-15 so it's not bound by Part 73. It's called "WBDH" & operates big band/nostalgia/old-time radio on 580kc. & gospel on 1570kc.. My understanding is that each stream is fed by a Kahn ISB receiver.

On the other end of the spectrum, there's a C-QuAM amateur station with audio samples available on the A.M. Window. Look up the callsign WA2FNQ. He also has his own site with a page devoted to brief histories of 3 of the A.M. stereo systems: Magnavox, Motorola & Kahn. He uses C-QuAM although my interpretation of Part 97 leads me to believe there's no law against an amateur station transmitting any of the other systems, if the amateur is so inclined.

 

[Ai4i]

I also had a magnificent Sony boombox (don't remember the model #) that...decoded all...competing systems.

The SRF-100? I had an SRF-1 walkman.
KH would decode in one switch position and all the other systems would decode in the other position.
No pilot tone sensing, so placing the switch in the wrong position would simply produce an out-of-phase false stereo effect.

Asymetry on Cquam: I believe that less than perfectly symetric modulation would shift the balance from center toward a side, though I do not remember which side, on at least some receivers (including my old Rat Shack TM-152 tuner).

Actually, the best systems are rarely chosen:
FM stereo never needed to have a 20dB disadvantage under FM mono.
Field sequential color TV has precisely the same robustness as monochrome.

 

[RadeoEngineer]

Yes Ai, I believe it was the SRF-100. You had to select the correct switch position and it sounded awesome.