If not AM HD, then ???

[Kmagrill]

Let's advance the premise that AM HD fails. I'm not saying that will happen, just posing this as a hypothetical situation to bridge to the next question which is: What would you propose to replace HD/IBOC/IBUZZ/IBAC?

I would further suggest the following premises as givens:

1. Whatever it is has to have audio quality perceived to be similar to FM, or better.
2. It should provide noise immunity better than AM.
3. Stereo is nice, but optional. Frequency response and noise immunity are more important.
4. DXing is fun for some listeners, but doesn't pay the bills. Radio, in general, generates its revenue on the coverage within the primary service contour. In larger cities, city grade coverage may be the limit to reliable service due to more interference.
5. Analog AM is a failing medium and keeping it as it is doesn't seem to be an option. What drives listeners away is low fidelity and impulse noise. As a person that worked for AM when our station was number 1 in ratings and billing, it was eye-opening when the first FM hit the air with a similar format. Within one ratings period, we fell from 1st to 10th and the FM jumped to 1st. It happened all over the USA, then the world, because analog AM just isn't as good a medium in terms of quality. Analog stereo would not and did not change that. Even so-called wide banded AM radios don't sound as good as FM and are far more susceptible to impulse noise.

So, if not the current HD format, what would you propose to help AM radio compete in coming years?

Any technical aid to AM today would require technology that can mimic FM or CD quality within the primary service contour, or at least, primary community of stations. Anything less is going to be perceived as inferior. Currently, there are three (that I know of) technologies that potentially offer this:

1. Ibiquity's HD (IBOC)
2. DRM
3. Kahn's CAM-D

Each has it's own strengths and weaknesses.

CAM-D was basically Kahn's analog AM stereo system with monaural high frequency information transmitted digitally. The digital and analog transmissions are blended together in the receiver, in real time, to produce a more natural sounding broadcast. The digital portion of the signal, being mono, reduces the perceived stereo effect while the analog AM portion leaves the receiver susceptible to traditional AM impulse noise. The analog portion also required that the receiver be flat to 7kHz, a relatively expensive proposal. CAM-D, as proposed, did not have a path to fully digital broadcasting in the future, however, it might have been possible to further develop the system to allow for this. CAM-D fits better within the AM spectrum mask, therefore does not significantly increase adjacent channel interference. CAM-D did fulfill one of the requirements: increased fidelity.

Digital Radio Mondiale (DRM) is an all-digital system popular on shortwave and suitable for AM. Because it does not have an analog component, DRM can only be decoded on digital receivers, of which there are very few available. Most are in Germany. The lack of backwards capability to analog AM is a sticking point for most USA broadcasters that don't want to lose their analog revenues.

HD's issues and strengths have been hotly debated and scarcely need to be rehashed yet again. It is a contentious debate with high emotions on both sides. Technically, HD is a hybrid system, meaning that it can be transmitted simultaneously with analog AM, or it can be turned into a fully digital system with enhanced capabilities. Currently, HD is the only system with a significant number of available receivers in the USA. Would turning off analog and going fully digital be a solution? Maybe in the long term, but until every radio is HD capable, there will be a lot of problems with any system not incorporating some analog capability.

There may be others and other methods may be yet invented.

As a generalization, any technical solution offered needs only be effective within the primary service area for the AM station. While it's interesting to be able to listen to stations many miles away, most stations do their selling within their 5mV city grade service contour with a smaller number still selling as far out as the 2mV service contour. No doubt there are lots of exceptions to this, but it should hold true for most situations.

So, the question is what are the most effective ways to improve AM radio within the 5mV contour?

Power increase? Maybe. Enforce part 15? Definitely, a good idea, but none of these address AM's underlying weaknesses.

Digital? Probably, but there are no perfect solutions on the table. We may have to settle for in imperfect system. Can the existing HD system be improved?

What constructive solutions would you propose or advocate to keep AM viable?

 

[Darth_vader]

As unlikely as this speculative idea (or any presented in future posts) is/are to happen, out-of-band DRM on 1720-2300 kHz (or below the 25 MHz HAM and CB bands) would be a start.

You may as well forget about CAM-D. I think it's safe to say that system's pretty much dead/stillborn at this point in the game.

"5. Analog AM is a failing medium and keeping it as it is doesn't seem to be an option."

No, analogue mediumwave broadcasting is a failling medium and keeping it as it is doesn't seem to be an option. Andlogue AM is still a very viable modulation system and is very widely used around the world, particularly on shortwave, VHF aircraft communication (108-135 MHz) and other two-way systems and in analogue television systems.

"analogue AM just isn't as good a medium in terms of quality. MW stereo would not and did not change that. Even so-called wide banded AM radios don't sound as good as FM and are far more susceptible to impulse noise. "

Nope. Although the crappy, narrow receivers on the market these days are part of the problem, an even bigger part of the problem is the miserably narrow bandwidth the MW signals go out with. Doesn't matter if you have a $5 000 receiver with a nice 15 kHz front-end; if the signal is only 4-5 kHz wide, it's still going to sound like crap on even on the widest of radios. Given enough bandwidth, a MW AM signal *can* sound excellent and almost FM-like, but only if whomever's putting the signal in the air wants it to.

But if you want to argue it as a matter of receiver design, then with today's DSP radios, all it would likely involve is adding or tweaking a few lines of code to get a nice wide front-end.

 

[K6JHU]

You can't make an Omlet (or souffle if your a Dr. Who fan) without breaking eggs. The question is how many eggs you want to break. There is no real solution without breaking a whole lot of eggs.

10 egg solution - keep AM IBOC as is with all it's adjacent channel flaws.
50 egg solution - go full digital IBOC after a sunset date. Need to get receivers out there.
100 egg solution - kill about 60+ per cent of stations and let the remainder go higher power and wider bandwidth
500 egg solution - create a new digital band and move the AM stations to the new band. Close down AM. Take that back. Maybe leave a couple of clear channels for coverage in the boonies.

 

[tomservo]

I'd be happy if the FCC and power companies took AM band interference seriously. I think if we could eliminate noisy power lines, BPL and other band-killing offenders, then AM would be fine the way it is — or was before HD. 10 kHz audio is adequate for talk and C-QUAM stereo is a good addition for many stations. 15 kHz would be better but as K6JHU says, it's a 100 egg solution.

I would be very happy to have AM stations migrate to the 76-88 MHz spectrum if we could convince the FCC it was a good idea. Make the band HD-only and give existing AM stations first dibs at providing equal or greater coverage. After a decade of mandated 76-108 MHz FM receivers, we could begin culling AM transmissions and retaining regional or superregional coverage as a speciality of the band, with 15 kHz fidelity again.

I know all the HD haters will poo-poo this idea, but the lure of a lower power bill (eventually) and multiple streams might be enough to convince smaller stations to make the jump.

What's to keep it from happening? The broadcasters themselves. No one wants more FM competition as it is; it was a fear of competition that led to the disastrous IBOC we're stuck with now. Until broadcasters wake up and realize everyone's in this together, AM & FM both will continue going to way of the dodo bird due to online listening of non-local sources.

 

[w9wi]

No, analogue mediumwave broadcasting is a failling medium

Drop the "analogue" part & I'll go with that..

..I don't see where any modulation scheme is going to help in the 530-1710KHz frequency band. Heck, I'd bet replacing 530-1710KHz with 42-44MHz -- while still using the same plain 'old AM modulation -- would be enough to save it. Except for that thing about nobody having any receivers .

I concur that nighttime skywave coverage outside the station's market is not economically useful. However, I'm thinking eliminating the Class A skywave protection is going to cause problems *within the market* for many stations & markets. Markets have grown, geographically, quite a bit since most stations were built. Here in Nashville, 50 years ago you could probably be successful with a signal that only covered Davidson County. None of the bordering counties were populous enough to matter, and all the money was in the city. Today, no station is going to be truly competitive if it can't reach heavily populated, rapidly growing, and *rich* Rutherford & Williamson Counties. "Let out" the pattern at WNMT 650 in Minnesota; do you end up with interference to WSM *in suburban Nashville*? (and does Minnesota actually get any useful new coverage -- or does WSM interfere with WNMT in all the newly-"served" areas?)

Or to be brief, I'm afraid you'll break down the coverage of the Class A stations *within their markets* while only providing interference-laden "service" somewhere else.

As K6JHU suggests, I don't think there's a solution for AM that doesn't involve "breaking eggs". There are far too many stations for the frequency band. Either you move to a higher frequency band where you've got more space (and no skywave to worry about), or you get rid of a bunch of stations. (I don't think 60% is enough, I think 80% is closer to what you'd have to do)

If you move to a higher frequency band I don't know that it much matters what modulation you use. Of course, by the time enough people had receivers for the new frequencies, the old band would probably be dead.

If you get rid of 80% of stations... by the time the Supreme Court got tired of hearing appeals from some 4,000-something station operators the old band would probably be dead.

I think the thinning-out thing is going to happen, but far too slow to do much good, and without any help from the FCC, Congress, the NAB, or anyone else except the (non)-listening audience.

 

[Kmagrill]

It seems to me that interference from other broadcasters is really a red herring of an issue. Yes, I know it exists in many places, but the issues that drive away local listeners is primarily fidelity and, to a much smaller degree, impulse noise. I'd suggest that the far bigger problem for most listeners is interference from our environment.

So, we all know that fidelity is primarily a receiver issue issue, but there is that nasty impulse noise issue that rears its head when wider banded radios are introduced and, in the end, AM never has a sound that competes with FM, even on pretty good AM tuners. And, of course, it costs more to make a good AM receiver than a bad one. Unfortunately, this is not true of FM where event he poorest receiver can still sound good. We know that AM stereo isn't a solution. Two channels of low-fi audio with a lot of additional noise added just isn't very appealing.

Since the FCC seems unlikely to move AM stations to another band, we're stuck with the MW band for now. Even if there was a migration, it would take decades before enough receivers were in place to make it commercially viable, so this does not seem to be an option, or does it? Could some technical advantage be sown into the fabric of a new band proposal that would have the public lining up the buy new radios? Of course, it would still take years to migrate.

So, we have amplitude modulation on a band that's very susceptible to noise, but even on higher bands, AM's still very prone to impulse noise. Someone mentioned aircraft radios and analog TV, both of which use AM. Anyone that ever watched analog over-the-air TV during a lightning storm, or even when a car with leaky spark plug wires drove by, knows that AM for TV was a noisy compromise. It was chosen because AM could fit color video into a 6mHz channel and FM could not. In the aircraft band, lightning from 100 miles away is clearly heard crackling through the headphones, even when the aircraft is close to the airport. AM was chosen over FM because there's no capture effect with AM. If two aircraft talk at the same time, there's a loud heterodyne, but both pilots can be heard through the noise. FM's capture effect would have prevented this, so AM was chosen because of that.

I concur that nighttime skywave coverage outside the station's market is not economically useful. However, I'm thinking eliminating the Class A skywave protection is going to cause problems *within the market* for many stations & markets. Markets have grown, geographically, quite a bit since most stations were built. Here in Nashville, 50 years ago you could probably be successful with a signal that only covered Davidson County. None of the bordering counties were populous enough to matter, and all the money was in the city. Today, no station is going to be truly competitive if it can't reach heavily populated, rapidly growing, and *rich* Rutherford & Williamson Counties. "Let out" the pattern at WNMT 650 in Minnesota; do you end up with interference to WSM *in suburban Nashville*? (and does Minnesota actually get any useful new coverage -- or does WSM interfere with WNMT in all the newly-"served" areas?)

Well, maybe yes and maybe no. Perhaps some useful research should be done in this field so that we don't have to speculate. It'd be interesting to see how changing powers and patterns might help some stations. The trick is to find out how to increase the local coverage without destroying someone else's local coverage. Nobody's come up with new standards in many decades and there have been some antenna design advances made that could have a bearing. This needs to be researched far more than has been done.

 

[Savage]

I vote for Leonard's CAM-D. And as a transitional phase, I advocate:

a. Reverse/eliminate NRSC preemphasis filter/EQ, which was devised for a receiver standard never implemented.
b. Mandate C-QUAM stereo (I disagree with your premise that stereo is unimportant. It's very important from a marketing standpoint.)
c. Allow 12.5 kHz bandpass day, 10 kHz bandpass night. Yes, I know that the daytime response puts the envelope outside the assigned channel, but no meaningful adjacent-channel problems would be created thanks to the existing allocation scheme. Certainly it would be NOTHING compared with the mess HD is causing at night.
d. Require all radio receiving devices (radios +) to be AM capable, and not only that, capable of sound quality equivalent to the device's FM response.

 

[rbrucecarter5]

I've made many suggestions here, I will repeat.

Although Kahn and Cam-D may be technically superior, no receivers exist. They are dead standards. C-Quam and Amax offer some hope of a standard going forward, because a fair number of car receivers still exist, and a fair number of HD radios decode C-Quam.

One - more - time: Most AM radios made today are wideband. Not through any desire by the manufacturer to make AM sound better, it is just cheaper to install one cheap ceramic filter. Especially when your tuning mechanism is substandard and the user can't get on frequency. +/-40 kHz is pretty typical, and Amax would sound absolutely great in mono over those cheap radios. I say "cheap" in the design sense, I've seen thousand dollar AV receivers withe the same substandard ceramic filters.

We need a meaningful international treaty to stop border blasting - both northbound and southbound. Some leakage will occur, but the plain fact of the matter is - people don't speak foreign, don't want to speak foreign, and won't learn foreign. So US citizens are not a potential audience for Mexico, and Mexico is not a potential market for US stations. Displaced citizens of one country have left the service area of stations in their home country. They should not expect to receive them in their new country of residence. Technology exists to keep signal largely in borders, it needs to be done! We need everybody in North America involved in a listenability conference, that includes Cuba - which would be glad to get rid of border blasters from the US. Put all allocations on the table, and arrive at something that serves the citizens of every country by eliminating interference from others.

We need a re-allocation of the AM band in the US, with the vast majority of US stations being relegated to graveyard frequencies - which need to be increased from the current number of 6. Everything from 1230 to 1490 for example. Anybody that has "critical" and "pre-sunset" hours now has to move to a graveyard. Don't cap the power during the day, but cap it at night to keep the overall noise floor reasonable. Guarantee of protection over their city of license, no guarantee outside. Allow super-regionals that serve two to three cities of license. Maybe from 910 to 1200. Allocate no more than 20 or 30 in North America. Allow superpower clears that can shout over interference and penetrate buildings locally, and serve rural listeners out of market. No more than three allocated at night in the lower 48, Canada, and Mexico. 530 to 900, and 1610 to 1700.

Move as many stations as possible to an extended FM band below 88 MHz. Risky for those stations until new receivers penetrate the market, so they will be allowed to hold onto their existing AM license with a sunset date 10 years in the future.

Open the longwave band to AM broadcasters. Under the same conditions as extended FM. With GPS, the aviation beacons are outdated hopelessly. Why continue using an outdated service tying up valuable spectrum? Investigate whether the longwave band can be extended in range to further help congestion.

 

[kenglish]

The trouble with creating a new, expanded analog FM Band (76-88 MHz, TV Channels 5&6) is that there are no radios, except hobbyist-type scanners, that can tune it. If stations can exist for 20 or 30 years with only a handful of listeners, until there are plenty of new radios, I guess they could try it.

There ARE receivers, already in every home in America, that CAN tune those frequencies. They are Digital TV ATSC receivers.
The sets are there, there are converter boxes there, there are even DVRs available for OTA Digital. Many people might need to replace their antennas with something capable of all bands (VHF+UHF), but even rabbit ears will work in some areas.

A single DTV channel can carry as many as 200+ audio channels, although you might want to eat up a small amount of BW for a fixed video image (logo, perhaps). These channels are all Dolby Digital, and can be anything from mono, to stereo, to 5.1 surround, as needed. A broadcast programming provider (that's, "what used to be called a station") could send one or more program streams to a transmission provider, who would aggregate all of the streams from a local market in to a single TV channel. You could provide your "main" program channel, plus supply several "sub-channels' with local commercial and programming insertion ("revenue streams"). Stations could transmit a high-quality mono "talk format" during some day-parts, stereo music during others, and surround sound for specials.

Of course, there would need to be a period of time where we continue to simulcast analog, or create formats that lend themselves to home-based listening, until there is enough interest to create portable and car radios that utilize the ATSC standards, with the ATSC-M/H (Mobile/Handheld) capabilities. But, you've already got a huge "living-room" audience, not to mention the kids with ATSC dongles on their computers.

Another advantage would be, translators would simply be a single ATSC translator for each RF channel. Imagine translating all of the stations in your market, using one box, rather than dozens of analog boxes at each site. All channels would be equal, since they all ride on the same DTV Transport Stream. You would not even be limited to channels 5 and 6...we might promote 5 and 6 as the "new FM band", but any other TV channels from 2-51 would be available for use in markets where they are open.

The biggest problem, right now, would be copyright laws, which currently prevent most radio broadcasts from being carried "on TV" without penalties.

 

[spunker88]

The issue is trying to broadcast a digital signal on the medium wave band. The way stations are allocated on the band, the effects of skywave, the noise given off by electronics, etc all make it very hard to receive a reliable digital signal on AM. Look on youtube for videos of lighting discharge causing HD to drop on stations being received close to their transmitters.

Most AM-HD stations already have an FM HD subchannel in their own market and some even have an FM analog channel. My way to fix HD radio on AM would be to eliminate it. Instead the AM station would send out a small digital signal along with its regular analog audio. This signal would tell the receiver what FM sub-channel to check for and verify reception by matching call letters before blending over from AM to the FM-HD subchannel. This digital signal on the AM band would be so low in bandwidth since its just sending small amounts of text, that it could be kept off adjacent frequencies and dropouts wouldn't matter since it would take very little time for the receiver to decode the data.

So for example a radio on WCBS on 880 would receive the data "WCBS-FM 101.1-3". The receiver would then check 101.1, verify reception with by matching the data from 880 and stored in the device's RAM (so it wouldn't have to tune 2 digital signals simultaneously) with the data from 101.1. If the calls match and the subschannel's audio is decoding then the radio's audio blends over. If the FM HD subchannel loses reception, then the radio falls back to the AM signal.

Personally I would just leave everything analog on AM, but if stations want a way to make the listener's audio blend to a less noisy signal, then this would be a way to do it. Of course you'd need new radios for this feature and transmitter adjustments, so this would probably never happen.

 

[spunker88]

The trouble with creating a new, expanded analog FM Band (76-88 MHz, TV Channels 5&6) is that there are no radios, except hobbyist-type scanners, that can tune it. If stations can exist for 20 or 30 years with only a handful of listeners, until there are plenty of new radios, I guess they could try it.

There ARE receivers, already in every home in America, that CAN tune those frequencies. They are Digital TV ATSC receivers.
The sets are there, there are converter boxes there, there are even DVRs available for OTA Digital. Many people might need to replace their antennas with something capable of all bands (VHF+UHF), but even rabbit ears will work in some areas.

A single DTV channel can carry as many as 200+ audio channels, although you might want to eat up a small amount of BW for a fixed video image (logo, perhaps). These channels are all Dolby Digital, and can be anything from mono, to stereo, to 5.1 surround, as needed. A broadcast programming provider (that's, "what used to be called a station") could send one or more program streams to a transmission provider, who would aggregate all of the streams from a local market in to a single TV channel. You could provide your "main" program channel, plus supply several "sub-channels' with local commercial and programming insertion ("revenue streams"). Stations could transmit a high-quality mono "talk format" during some day-parts, stereo music during others, and surround sound for specials.

Of course, there would need to be a period of time where we continue to simulcast analog, or create formats that lend themselves to home-based listening, until there is enough interest to create portable and car radios that utilize the ATSC standards, with the ATSC-M/H (Mobile/Handheld) capabilities. But, you've already got a huge "living-room" audience, not to mention the kids with ATSC dongles on their computers.

Another advantage would be, translators would simply be a single ATSC translator for each RF channel. Imagine translating all of the stations in your market, using one box, rather than dozens of analog boxes at each site. All channels would be equal, since they all ride on the same DTV Transport Stream. You would not even be limited to channels 5 and 6...we might promote 5 and 6 as the "new FM band", but any other TV channels from 2-51 would be available for use in markets where they are open.

The biggest problem, right now, would be copyright laws, which currently prevent most radio broadcasts from being carried "on TV" without penalties.

There are more radios out there that can tune down to 76Mhz than one might think, if you look at the specs of the IC used, the problem is most are disabled in software. For example some Japanese brand cars build their radios so the same IC can be used in the Japanese radios as well as the North American radios. With ICs being used in newer radios, even on domestic cars, it would probably be pretty easy to get 76Mhz-108Mhz radios out there.

But, I would also love to see radio on ATSC channels. The UHF band is in danger of having more spectrum sold off by the FCC. Audio channels would take up far less space than a video subchannel and if there was a way to make ATSC audio broadcasts compatible with existing ATSC equipment then you would already have a bunch of receivers out there. I'm not sure if audio only was ever an ATSC standard.

 

[rbrucecarter5]

The trouble with creating a new, expanded analog FM Band (76-88 MHz, TV Channels 5&6) is that there are no radios, except hobbyist-type scanners, that can tune it. If stations can exist for 20 or 30 years with only a handful of listeners, until there are plenty of new radios, I guess they could try it.

That is EXACTLY the problem with HD radio - it requires new radios, so it would take a long time to gain critical mass with consumers. Same with a scheme to re-program AM stations to automatically tune to FM. There simply are not enough translator frequencies available to move every AM station to FM, and even if you add in HD-X capability, coverage with HD radio still sucks in comparison to AM. Most of the problem with AM is the programming, not the transmission system. Foreign language brokering, ethnic, splinter formats, and an assortment of successful talk and sports stations are not compelling enough to get people to tune over to AM. Especially younger people to whom 6 stations all carrying the same talk show is just not interesting.

 

[kenglish]

.......But, I would also love to see radio on ATSC channels. The UHF band is in danger of having more spectrum sold off by the FCC. Audio channels would take up far less space than a video subchannel and if there was a way to make ATSC audio broadcasts compatible with existing ATSC equipment then you would already have a bunch of receivers out there. I'm not sure if audio only was ever an ATSC standard.

ATSC has provisions for audio-only channels. I'm not sure if they would allow for a full transport stream of audio-without-video, but the video could be a very low bandwidth one...maybe as low as a 100 Kb screen-saver.
There is a mode that allows for "audio-only", with no video associated with it, so most receivers will show a blank screen, or an intermittent "audio channel" screen-saver, floating by.

Other modes allow one (or more) different videos to be associated with the different audios, so you could even have a few logos that indicate the formats...."Digital Radio: Rock", or "New York Digital Radio: Country", etc.
Some of the oldest DTV receivers had some issues with doing alternate audio channels, and had the PSIP define entirely different channel names (Channel 4-1 for English, 4-11 for Spanish, etc), with the same video PID on all of them. Many newer sets seem to allow for only three audios on a single program (often labeled English, Spanish and French), so you might have to label them by program channels, like I mentioned.

 

[Kmagrill]

....b. Mandate C-QUAM stereo (I disagree with your premise that stereo is unimportant. It's very important from a marketing standpoint.)
c. Allow 12.5 kHz bandpass day, 10 kHz bandpass night. Yes, I know that the daytime response puts the envelope outside the assigned channel, but no meaningful adjacent-channel problems would be created thanks to the existing allocation scheme. Certainly it would be NOTHING compared with the mess HD is causing at night.
d. Require all radio receiving devices (radios +) to be AM capable, and not only that, capable of sound quality equivalent to the device's FM response.

Well, we tried AM stereo in 1986. I put two c-quam AM stations on the air. Our flagship AM station was in Salem, Oregon which is the state capitol. It was 5kW day and 1kW night non-directional using a half-wave tower. The station had a great signal. In my '86 Z28, there was a factory installed c-quam radio. In stereo mode it went into "Wide" band operation which was 6.5kHz (vs 3.5kHz in standard mono mode). We did oldies with live morning, midday and afternoon drive shows. The sound on any AM stereo radio was never competitive with FM and, while the station broke even financially, it never did any better when it had c-quam than when it didn't. There was no ratings gain nor anything to justify the $60,000 invested in a new c-quam capable transmitter and exciter and mod monitor.

I don't think there's any evidence that AM stereo even has a marketing benefit. Indeed it may well be the reverse. When people listen to AM stereo for the first time, they expect it to be Hi-Fi. They tend to be rather disappointed when they discover that stereo does not mean hi-fi.

.... Most of the problem with AM is the programming, not the transmission system. Foreign language brokering, ethnic, splinter formats, and an assortment of successful talk and sports stations are not compelling enough to get people to tune over to AM. Especially younger people to whom 6 stations all carrying the same talk show is just not interesting.

While programming on AM may be (generally speaking) bad, that's a symptom, not a cause of poor listenership. AM radio was killed by superior performance of FM audio as a music medium. If the reverse were true, there would still be lots of AM stations competing for listeners, as we tried in the '80s. Remember that in the 60s and early 70s, AM was king and a goldmine. Most AM stations didn't give up on their music formats too easily. They tried hard to compete with FM, but the AM medium just doesn't lend itself to hi-fi audio very well.

 

[Savage]

AM Stereo was never given an adequate chance. I was also there in 1980-1988, when the AM Stereo wars were raging. In my experience with 50kw AM stereo music stations, the standard was starting to catch on, and C-QUAM sounded superb on the then-available receivers. Really, for practical purposes, the C-QUAM "era" only spanned about three years, after which impatient operators started scrapping it when it didn't "fix" audience loss which was mostly caused by lousy programming.

I will partially agree that "stereo" is a relatively minor component of my proposed AM fix, but I still argue it's important. The urgent priorities are, in this order: (a) stop AM HD, (b) scrap NRSC, (c) open up bandwidth, (d) immediately start policing noise generation, (e) mandate receiver/receiving device standards.

I recognize it's unlikely given the voracious appetite the Federal government has for money (taxation) but a generous tax credit for operators who turn in licenses for worthless AM facilities, like hi-dial lo-power daytimers with no PSA or PSSA hope, would help de-junk the band.

I also like the proposal for a new NARBA conference to get rid of borderblasters.

 

[K6JHU]

From a technical viewpoint the ATSC low band solution is a 10 egg solution.

The issue is now that you have 100 channel capabilty and only 20 some odd AM stations per city, what happens to the extra space?
A good reason for broadcasters not to like that

 

[Darth_vader]

is that there are no radios, except hobbyist-type scanners, that can tune it."

Wrong. They're called "MW/FM/VHF TV audio" receivers, and have been widely available since probably the '70s, if not earlier. Available for $5 at a Goodwill near you. Even more are undoubtedly currently available, but not immediately "visible" for the reason spunker88 gives in his opening sentence.

"I'm not sure if 'audio-only' was ever part of the ATSC standard."

It is, just like with DVB. In fact, OPB were doing such a thing on -04 (later -03) when they first started simulcasting KOPB-FM on an experimental basis several years ago. Most receivers will display an "audio only" banner on-screen or some other sort of graphic stored in ROM, if they don't just output a black field. w9wi could probably tell us more about it.

 

[satech]

Extending the FM band down to 76 MHz is the best solution. Radios with 76-108 MHz FM have been in production for decades by Japanese brands. No re-designing would be needed to have manufacturers start selling those radios here. All they would need to do is change the diode, jumper, or firmware programming which tells the radio which FM band to use. Many existing U.S. market radios can be reprogrammed to 76-108 MHz just by holding down a certain combination of buttons (although this usually also switches the AM band to 9 kHz channel spacing).

 

[tomservo]

You think HD radio is hard to get while moving, try tuning an ATSC channel. It's damn near impossible unless you're staring at the tower.

 

[w9wi]

satech: 76-88MHz is not available in Philadelphia, southern New Jersey, Delaware, Washington DC, and most of Maryland. Among other less-populated areas.

76-82 is not available in most of Tennessee; in Milwaukee, Chicago, in the most populated part of Michigan (pretty much the entire southern third of the state), in northwest Ohio, and in northern Indiana, again, among other less-populated places.

82-88 is out in much of Alabama among other places.

The TV stations in those bands would rather not be there, but (especially with spectrum refarming) there's nowhere else for them to go.

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Darth_vader: Basically, an ATSC DTV station can broadcast a program ("virtual channel") containing some number of "elementary streams" - including audio and video. Zero is a valid number of video streams.*

The ATSC standard doesn't (to my knowledge) specify what a TV should do if there's no video stream. In the few cases I've seen, the TV puts up an internally-generated still indicating this is an audio-only program.

The program specifies elementary streams by protocol ID. There's nothing to prevent more than one stream from referencing the same protocol ID -- the same elementary stream. So a station could broadcast a single still slide & link it to a dozen or more different programs with different audio streams. You'd only transmit the video once -- and as a still, it would compress REALLY WELL.

I am aware of DTV stations in Atlanta and Oregon carrying audio-only programs, and a station in Milwaukee carrying "radio" stations whose video stream consists of a single slide describing the selection currently being broadcast.

* to my knowledge, a figure >1 is also valid -- although I have no idea what a TV would do if it encountered a single program with more than one video stream!