I'm not sure what kind of compression analog FM signals use, but they obviously don't sound as good as CD's (ignoring the freq. response differences). If you compared these:

#1) Cream "White Room" on Onkyo model #900 CD player > low pass and high pass filter to simulate FM's freq. response > Onkyo model #2500 receiver > Polk model #500 speakers

vs.

#2) Cream "White Room" on Onkyo model #900 CD player > analog FM transmitter > Onkyo model #2500 receiver w/good FM stereo reception > Polk model #500 speakers

#1 would always win. This indicates some type of lossy analog compression or signal loss to me. I doubt any radio station plays mp3's made from CD's as source material for their broadcasts. An exception may be made for voice clips, and one time about a year ago I heard a FM station broadcast a leaked-to-the-net track from GNR's upcoming Chinese Democracy (will it ever see the light of day?). I could tell the GNR track was a low bitrate mp3 because of all the wind-chime effects in the highs.

OK I did a little reading about HD AM and HD FM radio and the consensus is that it does use lossy compression although it wouldn't state it explicitly:

http://www.elecdesign.com/Articles/I...eID=12194&pg=1

"How does the system work? First, the audio content is digitized and then compressed, according to iBiquity's HDC codec, to reduce the overall bit rate and required transmission bandwidth. Next, the signal is multiplexed with the other digital data to be transmitted."

The digital signals share bandwidth with the analog signals. From what I read there isn't enough bandwidth available in the FM and especially AM bands to be able to deliver lossless compression, much less true high definition (24/96 or 24/192 x 2 ch or 5.1 ch). It will still be 16/44.1. The freq. response of analog AM sucks, that is why it is inhabited primarily by talk radio stations now. HD digital AM will improve the frequency response to that of analog FM, and HD digital FM will sound like a mid-quality mp3 (is that better than analog FM? Not in my opinion). There is a lot of controversy about this new format and a lot of the comments below the main article are great.

I am not a luddite, I love the convenience of the internet and downloading music and movies. Taping and trading has taken a huge leap forward from the days of real time copying cassette tapes and generational loss of quality. However, a lot of the "improvements" of the digital age are just a marketing scheme utilizing planned obsolescence. First CD's come out, and many touted its compact size and great sound (dubbed "perfect sound forever" ). A lot of audiophiles thought they sounded harsh and lifeless, dubbed them lossy, and continued to listen to the gorgeous, lifelike sound of their stereo vinyl LP's. Then SACD's (inferior to CD's at high frequencies because of its flawed 1 bit system) and DVD-Audio (a definite step forward) came out. I bet that every ten years or so in the future they will incrementally step up the quality of digital audio (and video too) by using a higher bit depth/sample rate, so that people will re-purchase albums recorded in analog and buy new source components. Digital cameras are a big improvement, right? No more pesky film to buy and deal with, no more trips to the developer to pick up prints. Except experts agree that film-like quality won't be achieved until cameras have about 20 megapixel resolution. When dig cameras first came out what were they, like 1 megapixel, if that? Every new year's models had incremental improvements of like .5 megapixel. It's a MFing rip-off!!! All those DVD's that have been sold over the last 10 years, obsolete. CPU processor speeds lurched forward at like 20 MHz increments at one point. Was this all because research and development hadn't caught up yet? No, they were holding back the best stuff to release later!! ::Rant over, continues to DL and UL obsolete DVD's::

A great post from the terrestrial HD Radio article:

I have had a 27 year career as a broadcast program director and engineer, mostly of classical music stations that featured superb audio quality. The reason that I *no longer listen to FM radio* is because of multipath. Our American FM stereo system, adapted all over the world, is a defective process using a noisy, interference prone amplitude modulated "difference" subcarrier. It was a bad decision in 1961, when it was approved by the FCC; but it was compatible with existing equipment. I tried my best as an engineer -- and a developer of broadcast transmission and processing gear -- to cope with its limits. I retired from the business in 1991 and was GLAD to be out of it. Digital audio via compact disks was SO MUCH BETTER that I never looked back! I tune in the FM bands, about once a year, just to check. They have become progressively worse, with heavy processing and clipping distortion, to the point of being pure noise and hash, and interference from too many stations. Pitiful!

IBOC has not helped this situation one bit, if one does NOT have a digital radio. It has made AM radio INFINITELY WORSE. The digital subcarriers bleed all over the now-duller frequency spectrum of the analogue audio signal, causing a hiss or even a gurgling sound that almost totally obliterates the intelligibility. Recently San Francisco's station KNEW has added some new "feature" to their digital transmission that results in making the station unlistenable at all on MOST of my radios. I have given up listening to the station, which is surely not what the management and program directors intend me to do. I can only assume that they are so ignorant of what the result is, in the field away from their studios and in the local environment of their 5 and 2 mv signal contours, that they have no clue that what they are doing to their OWN signal is, in effect, to "jam" it. I might guess that 10, 20, or perhaps even *50* listeners in the bay area are able to hear the improved digital signal...but everybody else, with standard AM radios, hears a worse signal. Is this progress?

So, what has happened is a close parallel to FM multiplex stereo. A bad, compromised "compatible" system has been shoehorned into the available RF spectrum. Very little testing has been done -- and my guess is that most of what HAS been done to test the system is very biased -- and the regulators just "roll over" and accept the blandishments of the supporters of the scheme.

Early FM multiplex stereo had TERRIBLE audio problems. Not only was multipath now a much worse problem than in the "pure mono" FM days, but also the intrinsic signal to noise ratio was degraded; clean reception area vastly reduced; and even listeners with the BEST equipment suffered from constant problems of audio distortion products due to the lousy, primitive, underdeveloped stereo generators of 1961-2 vintage (including severe problems of intermodulation, transient distortion and overshoot, and aliasing products: not solved until FM multiplex had existed for another 15 years, largely by my friend and associate Bob Orban.)

The same thing will surely happen with IBOC. I am merely experiencing the repetition of history. A good, solid, mature broadcast system -- double sideband amplitude modulation, in mono -- has been wrecked by adding to it what conventional receivers perceive as a spurious interference product. It will be MANY years before all of this is sorted out. Meanwhile, the shrinking share of market of marginal AM stations will simply drive them into greater loss and unprofitability. But the makers of fancy new digital gear will LOVE it, even if no one listens! Once they sell the first generation of the (barely working, primitive) system, they will start upgrading, improving, and perfecting what will become the next generation...so on, so forth.

I have a question to everyone involved in this absurd farce. What happens if a certain threshold of pain is reached in the minds of AM radio listeners, and EVERYBODY gives up listening?

Is this really the AGENDA?

Steve Waldee retired AM, FM broadcaster San Jose, CA.