Time to reconsider AM stereo?

[audioguy]

I think many of us are of the opinion that HD AM is not going to make it. However, AM owners do not want to go empty-handed.

Is it time to reconsider AM stereo, in order to enable AM radio to be reasonably comparable to FM? Today, stereo transmission is the standard, so any broadcast system needs to at least provide that. Given the limited amount of AM spectrum, C-QUAM seems like an efficient way to provide improved service.

Does anybody know: How many HD radios can decode C-QUAM? How many analog AM stereo car radios are still in circulation?

Are there any tweaks that could/should be done that would improve C-QUAM if it were to be re-launched?

Could C-QUAM be successful if it got a fresh launch with some decent marketing? Starting with a more user-friendly name than C-QUAM?

C-QUAM AM stereo, while far from being perfect, does have many advantages over HD AM. In particular, it does not cause additional interference. The service area of an AM signal is almost the same in stereo as it is in mono. And if properly set up, it has decent audio quality, although not as good as analog FM (and we will not try to pretend otherwise).


http://en.wikipedia.org/wiki/C-QUAM

[clouseau]

You may in fact be correct.  AMHD may not make it.  However I believe that is a function of AM radio overall.
While AM Stereo MAY be superior to AM mono, AM overall isn't looking all that good.

With the utmost deference to our AM compadres, more and more, AM is showing up as ratings leaders less and less.  I wouldn't expect that trend to change. 

I suspect the future of AM radio is with FM translators and maybe with TV CH 5 & 6.  Actually I suspect we will tentatively decide the 5/6 issue sometime in August, when LPTV either gets it or has it delayed.

Either way, I think you're fighting an uphill battle to get another 50 cents spent in AM radio technology for stereo in receivers.

Clouseau 

[Play Freebird]

Either way, I think you're fighting an uphill battle to get another 50 cents spent in AM radio technology for stereo in receivers.

With today's technology, it can probably be done for less than that -- and this would certainly be less expensive than HD.   Haven't Motorola's patents expired by now?  If so, royalties shouldn't be a concern.

[KB1OKL]

I think AM stereo is great, had it in an 88 Plymouth, I can remember hearing AM stereo stations from 100's of miles at night. I have a Meduci AMX-2000 stereo tuner right now that receives C-QUAM, unfortunately there are no C-Quam stations within my listening area at all.

[radioman148]

I liked AM stereo, but with so much talk on AM I doubt it would help much now.

[Peter Q. George (K1XRB)]

I liked AM stereo, but with so much talk on AM I doubt it would help much now.

I look at it, this way.  HD-AM simply doesn't work, period.  What can be done right now is to reconsider switching back to C-QUAM Stereo and get rid of those horrible brick wall filters.  C-QUAM will decode on many IBOC receivers, due to the chipset already in place.  C-QUAM is already THE system in place for AM Stereo according to the FCC Rules and Regulations.  Hey, it can't hurt and the quality on standard (mono) AM receivers would improve due to the inheritant abilities of the Motorola C-QUAM AM Stereo system.  Over the years, C-QUAM has improved.  The "platform motion" has been pretty much eliminated do to the better circuitry made over the years.   Let get rid of HD-AM and the splatter (hiss) that comes with it, once and for all.   

[Savage]

Amen to that.  I have long been an advocate of a revision to the NRSC standard allowing 12.5 kHz bandwidth daytime, 10 kHz nighttime with the standard pre-emphasis curve MANDATORY for all USA receiver sales.  Also AM stations should be encouraged to program C-QUAM fulltime.

The sound quality improvement would be well worth the slightly increased adjacent-channel splash, which would in turn be vastly less objectionable than that caused by HD sidebands.  With the current US allocation standards any splatter wouldn't be troublesome to other local or nearby signals for the most part.  Of course - unlike HD - the rule could also be crafted in such a way that any wideband AM causing harmful interference to an adjacent would be required to dial back to 10 kHz-U.

We could market it as "Hi-Fi AM" or some similar trade name.  Actually, the way most FMs are processed these days, a 12.5 kHz-wide AM stereo signal would sound better and more realistic than many FMs.

I have always been of the opinion that C-QUAM AM stereo sounded better than FM stereo.  It is truly an excellent system.

[rbrucecarter5]

Is it time to reconsider AM stereo, in order to enable AM radio to be reasonably comparable to FM? Today, stereo transmission is the standard, so any broadcast system needs to at least provide that. Given the limited amount of AM spectrum, C-QUAM seems like an efficient way to provide improved service.

I think one unwanted side effect of the HD-AM movement was that it killed C-Quam AM stereo completely.  The few stations that still carried it for music formats quickly switched to the new technology, leaving very few C-Quam stations on the air.  Those that didn't care about audio quality never had C-Quam and won't adopt HD-AM (thankfully). 

The HD shills were very quick to falsely accuse C-Quam of limiting a station's range - in spite of overwhelming evidence to the contrary.  I did testing in a valley 290 miles away from some Dallas stations in the daytime - and they decoded just fine in stereo.  How much freakin' range do station owners want?  Especially when one of those same stations would not decode HD less than ten miles away.  Let's see - 290 miles vs. less than 10 miles - which stereo system would YOU pick for YOUR station?

I agree that C-Quam would be vastly superior to HD-AM, but iBiquity backing off of it to promote C-Quam?  Even re-branded?  I don't think so.  Those folks have proven to be vindictive and under handed, using high pressure tactics and outright lies to scare off all criticism of their faulty system.  Their colossal egos refuse to admit that they are wrong, so they will cling to the sinking boat until they drown at the bottom of the ocean rather than take a life preserver like C-Quam.

[w9wi]

I think many of us are of the opinion that HD AM is not going to make it. However, AM owners do not want to go empty-handed.

Is it time to reconsider AM stereo, in order to enable AM radio to be reasonably comparable to FM? Today, stereo transmission is the standard, so any broadcast system needs to at least provide that. Given the limited amount of AM spectrum, C-QUAM seems like an efficient way to provide improved service.

Does anybody know: How many HD radios can decode C-QUAM? How many analog AM stereo car radios are still in circulation?

Are there any tweaks that could/should be done that would improve C-QUAM if it were to be re-launched?

Could C-QUAM be successful if it got a fresh launch with some decent marketing? Starting with a more user-friendly name than C-QUAM?

C-QUAM AM stereo, while far from being perfect, does have many advantages over HD AM. In particular, it does not cause additional interference. The service area of an AM signal is almost the same in stereo as it is in mono. And if properly set up, it has decent audio quality, although not as good as analog FM (and we will not try to pretend otherwise).


http://en.wikipedia.org/wiki/C-QUAM

IMHO AM stereo addresses the same problem as IBOC: poor audio quality.  (perceived or real)

Thing is, poor audio quality is not what's fundamentally wrong with AM. 

The fundamental problem with AM is poor and unpredictable (by the average listener) coverage, especially at night. 

At least AM stereo, unlike IBOC, doesn't make that problem worse!

I would suggest there has been one positive development that's come out of IBOC: the development of inexpensive receivers with digital signal processing.  Most listeners are finding that HD receivers have exceptional performance when tuned to analog stations.  AM operators should push for the inclusion of that technology in as many receivers as possible.  And yes, there's no reason they shouldn't be able to include C-Quam capability in the DSP firmware.

[ajc_trw]

I worked (DJ overnights) for an AM stereo station back in 1995 (KAZM 780 Sedona AZ) and the sound was quite good, for AM radio. C-QUAM's big problem was platform motion, but that was only a problem with a weak signal.

AM Stereo can sound quite good. When I first went into the air studio they were playing music and as I heard the monitors I didn't know if they were monitoring the board or off-air. I couldn't hear audio above 9kHz so I thought it was off-air but the dynamic range was too wide for broadcast (as I was used to it) so I thought it was from the board. KAZM definitely did C-QUAM right! :-)

As far as crosstalk, there is little to none. We had a cassette recorder on the board where we could record our air-check tapes. Unfortunately they only wired one channel from the off-air stereo monitor. Just listening to California Dreaming (male vocals on one side female on the other) testifies how little crosstalk there is in C-QUAM.

My recommendation: Widen the bandwidth to 12.5kHz, kill asymmetric processing and lighten up on the Optimod. All IMHO, YMMV.