Is it technically possible to have AM radio sound as good as FM? Years ago an acquaintance of mine who worked at a big AM station said that AM stereo sounded real good. I never had an AM stereo receiver to find out for myself. Did well-maintained AM Stereo facilities rival FM in sound quality? All I know is that, as a music listener, when I go from a major FM station to one of the AM music stations (Radio Disney and oldies stations) I notice the loss of stereo and the quality drop-off immediately. The Radio Disney outlet in Cleveland, Ohio has a slightly muddy, while at the same time kind of a poor or mediocre bass response to its sound.
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How?: AM as good as FM
- Thread starter johnbasalla
- Start date
Actually, AM sounds very good, provided you listen to the signal on a proper tuner. If you listen to an AM signal on a modulation monitor, you'll be surprised at the quality. The reason is that you're listening to the wideband signal, hearing the full spectrum. Most of us are use to hearing AM on a narrow bandwidth receiver.
Now, I've heard AM stereo, and I've thought it sounded very nice. I wouldn't say they "rivaled" FM, but they certainly sounded very good.
Now, I've heard AM stereo, and I've thought it sounded very nice. I wouldn't say they "rivaled" FM, but they certainly sounded very good.
johnbasalla said:
The real-world limitations to the quality of AM are mostly that 1) it is extremely prone to noise interference, and 2) any use of wideband ("Hi-Fi") audio invades adjacent channels.
If the modulation is kept linear, I know of no inherent theoretical limitation to AM audio quality. I would even go so far as to say that under laboratory conditions, AM will not only rival FM's quality, but exceed it, because AM does not require FM's pre-emphasis.
Beyond the above real-world limitations, in my view the theoretical (and practical) reason that makes plain vanilla AM transmission outmoded compared to other modulation methods is that it is extremely inefficient, requiring that most of its power be concentrated in a carrier. There are ways around this (e.g., SSB), but then we are no longer discussing the most basic form of AM.
Personally, even with as much affection as I have for traditional AM, I'd like to see high quality digital audio on the MW band using DRM with really wide channels. But I am in a very small minority!
Kind Regards,
David
WCSI in Columbus sounded better than Fm in the 1970's and early 1980's. They were playing music and I had no problem while listening on a Dymek tuner or similar. Now that is not the case. Some LPAM units sold have the same capability.
W
WCWalker
Guest
I can recall when I owned a Carver TX 11a tuner and tuned into CQUAM stereo AM signals. Hi Fi AM sounded much better than FM's over processed signals. The AM signals had a warmth that is missing with the FM signals.
One of the AM stations I work with in upstate PA put a new FM translator on the air last year, co-located with the AM transmitter. To save a few bucks, the owner decided not to purchase an FM processor -- he simply feeds the FM exciter from the second output of his Optimod 9200. Initially, I was skeptical of this approach, but it has actually worked out quite well. Due to the NRSC lowpass filter, his translator's audio is slightly duller than that of other FM stations, however, on most car and portable radios the difference isn't really apparent. The Optimod is set up for asymmetrical modulation (which, of course, carries through to the FM) causing a slight loss of loudness; FM negative peaks only reach 80 percent, but this 1 dB deficiency isn't a major factor in his largely-rural market. His format is a news/AC hybrid so he doesn't care much about stereo.
While driving around checking coverage, I realized that a listener to this translator would experience nearly the same quality of audio as someone who has tuned in his AM on an "ideal" AMAX-compliant receiver, so it provides a nice simulation. Most FM receivers have the attributes we wish for on the AM side: Good noise immunity, low distortion, frequency response out to 10 kHz (including NRSC-compliant 75 microsecond de-emphasis), and good adjacent channel rejection. I'll definitely take his translator's audio over the artificial sound of the AM HD codec.
While driving around checking coverage, I realized that a listener to this translator would experience nearly the same quality of audio as someone who has tuned in his AM on an "ideal" AMAX-compliant receiver, so it provides a nice simulation. Most FM receivers have the attributes we wish for on the AM side: Good noise immunity, low distortion, frequency response out to 10 kHz (including NRSC-compliant 75 microsecond de-emphasis), and good adjacent channel rejection. I'll definitely take his translator's audio over the artificial sound of the AM HD codec.
In the late 1980's, when I was the CE for WQYK-AM/FM, Tampa. We were transmitting the AM signal in C-QUAM stereo and simulcasting the FM audio.
Before the 10khz brick wall limit went into effect, many of the Jocks told me that they liked the sound of the AM signal better than the FM signal.
They told me that the AM sounded "bigger" (whatever that means).
Can AM transmit high fidelity. It certainly can. Analog TV video is amplitude modulated with a flat frequency response to something above 4MHz.
Of course, impulse noise is a problem but with good signal strength, AM can sound very good.
Before the 10khz brick wall limit went into effect, many of the Jocks told me that they liked the sound of the AM signal better than the FM signal.
They told me that the AM sounded "bigger" (whatever that means).
Can AM transmit high fidelity. It certainly can. Analog TV video is amplitude modulated with a flat frequency response to something above 4MHz.
Of course, impulse noise is a problem but with good signal strength, AM can sound very good.
The problem with the AM band as we see it isn't really so much the "Ancient Modulation" as some call it on the Business of Radio board here, but the location of the band in the electromagnetic spectrum. If we used amplitude modulation with a 10kHz mask, but moved the frequency to the VHF-low (approx 44 mHz), a lot of the problems we have with the sound quality on the AM band would go away. Of course, as long as we're moving bands, why not go to a 20kHz spacing? 
You also wouldn't be able to pick up WWL at night in Memphis.
You also wouldn't be able to pick up WWL at night in Memphis.
Based on the last few times I have been through MEM in the evening, how might this be different from how it is now? Somebody -- either Radio Reloj rocking the time-ticks, or a more-nearby 870 "forgetting" to turn the carrier off at sunset, or a combination of all of the above -- has been just chewing up the big 870.
frankberry said:
That bigger than life has to do with processing. FM processes based on the mono signal so the separation might appear limited. However, C-QUAM processes L-R separate from L+R so stereo separation is more pronounced.
AM can sound amazing through a proper receiver. However, 99 percent of the receivers on the market have telephone (or worse) bandwidth. Then there are the part 15 monsters.
AM can sound awesome.
I just finished building a 100mW AM transmitter using two tubes... yes, those glass things that glow in the dark. The response of this transmitter with a Urei 1176LN and an Inovonics 222 NRSC processor as an airchain is just splendid, even WITH the 10kHz filtering. It'll do well over 100% on positive peaks and actually sounds better than any of the local AM stations. With the NRSC disabled, it's flat out to around 14kHz. It sounds great on all my radios. It only covers my yard, but I think it sounds better than my FM trannys do.
If I had a good analog reverb to throw on it, it would sound like WOWO used to.
So, yes, AM can sound great. Digital processing makes FM sound like "plastic" IMO.
The FCC should stick a fork in AM IBOC. That's a friggin scam is all that is.
I just finished building a 100mW AM transmitter using two tubes... yes, those glass things that glow in the dark. The response of this transmitter with a Urei 1176LN and an Inovonics 222 NRSC processor as an airchain is just splendid, even WITH the 10kHz filtering. It'll do well over 100% on positive peaks and actually sounds better than any of the local AM stations. With the NRSC disabled, it's flat out to around 14kHz. It sounds great on all my radios. It only covers my yard, but I think it sounds better than my FM trannys do.
If I had a good analog reverb to throw on it, it would sound like WOWO used to.
So, yes, AM can sound great. Digital processing makes FM sound like "plastic" IMO.
The FCC should stick a fork in AM IBOC. That's a friggin scam is all that is.
Listening to KXEO Mexico, MO in AM Stereo on my HD Reciever, it sounds much better than HD-AM, and sounds at least as good as if not better than a few FMs in the area...(Still have a few people in the area using old Optimod 8000s on FM, and one station that has always sounded like it was broadcasting from the bottom of a well.
That was my baby 30 years ago. Monthly, I tweaked the 807 audio driver balance to maintain the 0.5% distortion, -59db noise & -3db at 15khz performance of the all tube Harris BC-500H. The FM pre-emphasis spec requires only +12db at 15khz on the transmit end. Assuming an FM receiver with -17db of de-emphasis and an FM transmission system with the minimum pre-emphasis requirement, WCSI would have sounded 'better' than an FM station. Not to mention that in the mid 70's, we were all using primitive FM processing like Volumax & (gag) FM Solid Statesman units. ChiefEngineer, along with myself, were on the air at WCSI...we listened to the mod monitor & heard our own voices come back through the headphones. I wholeheartedly concur that the 500 watt daytimer on 1010 did indeed sound better than all but the classical (translation = non-processed) FM stations. Until NRSC came along, AM was indeed capable of sounding superb. A few of us were 'into it' & fully maximized that potential. It's a shame that NRSC & IBOC have relegated that grand sound to a footnote in history.ChiefEngineer said:
Back in The Day, I remember the High Priest of Rock n Roll on WTOP, it sounded great. He'd do the daily bird call (for the Sparrows and the Crows and the Robin Red Breats, especially those Robins with the BIG RED BREASTS) abut once per show. It was comparable in audio to WWVA - FM, which was the other station of choice for us, with Music Americana for about 6 hours every night. On s decent radio WTOP had excellent audio.
I've found AM sounds amazingly well on the GE Super radio in the wideband mode. Even the narrow band setting isn't bad. But if you want to hear AM in it's purest form make yourself a crystal set using a diode instead of a crystal and a transformer in place of the ear phone. Tie it to your home stereo and you will be blown away by how good most AM's sound.
Yup.. Or a TRF set will do the trick too. Imagine how good it would sound without NRSC-2. It floors me that we can tolorate IBUZ, but still must adhere to nrsc-2. In my book splatter on a bad day is less destructive to neighbors that IBUZ is on a good day. Must be some of that famous NAB/FCC engineering logic I'm just missing or something.... Lol!
OKCRadioGuy said:
Amen! I find it amazing NRSC-2 was mandatory for broadcasters but receiver manufactures were exempt. What is the point?
I would have to say that CKLW using Motorola (maybe it started as Harris) AM Stereo rivaled FM Stereo on a Sony SRF-A100 in wide mode. But in Canada, they didn't have the same bandwidth restrictions. At night, adjacent channel interference limited this. If you were really close to a Class IV (Class C), some of them had great frequency response that rivaled Class I (Class A stations). Usually, directionals didn't sound as good because of the complexity of the antenna and sideband asymmetry associated with it.
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