Saving AM Radio

[davideduardo]

One would think a 750 watt (assuming 100% effency) for 50% of time 12 hours would show up in the power bill.

Not as much as you think. Much of a traditional plate modulated tube transmitter power goes to the oscillator and IPA stages as well as cooling fans and heat loss in tubes, transformers, etc.

An AM transmitter is not ever 100% efficient even with all the advances. One has to create the full power carrier and place modulation on top of it (which is why the signal component is called a "carrier" as it carries the audio on it).

50's and 60's era 1kw transmitters using two pairs of 833's or 4-400A's (QB4-1100 in European nomenclature) for finals and modulation would use over 2 kw of power.

Today's carrier suppression systems and solid state RF modules are more efficient, but AM itself can't produce 1kw in = 1kw out, ever.

 

[Kelly A]

Same with MA3, Digital Hash on adjusting frequencies

Actually it's much less because you take 5kHZ of analog modulation out of the carrier.

 

[yeoldeschool]

Not as much as you think. Much of a traditional plate modulated tube transmitter power goes to the oscillator and IPA stages as well as cooling fans and heat loss in tubes, transformers, etc. [...] 50's and 60's era 1kw transmitters using two pairs of 833's or 4-400A's (QB4-1100 in European nomenclature) for finals and modulation would use over 2 kw of power.

Do you happen to know the efficiency ranges that were common with the original generations of tube transmitters like the gigantic RCA 50A and 50B? I had a look through a few historical pages on them but other than mentions of individual tube characteristics, I saw nothing about total kW in versus total kW out.

One has to create the full power carrier and place modulation on top of it (which is why the signal component is called a "carrier" as it carries the audio on it).

Radio's pioneers choosing the term carrier always perplexed me because the carrier doesn't literally carry (in the sense of conveying) the audio. Maybe it's a chicken vs. egg thing, but it's the act of rapidly changing (distorting) a carrier's amplitude or frequency that generates the sum and difference frequency products that are the upper and lower sidebands that in turn are the spectral clones of the audio that dictated those very changes to its amplitude/frequency in the first place. Suppress that carrier afterward and you still have your audio as DSSC, or USB/LSB if you also remove a sideband. Somehow it would have made more sense had they called carriers pilots -- the same as they did with FM's DSSC stereo's carrier after halving its frequency to 19 kHz.

 

[davideduardo]

Does "hybrid digital" actually exist or is it a phrase invented by non-industry types as a guess for the meaning of the "HD" in "HD Radio." Turns out that "HD" stands for nothing at all; it's just part of the brand. So if HD Radio isn't hybrid digital, what is?

The folks at ibiquty said, over 20 years ago, that "HD" did not stand for anything. People in the industry decided on their own that it meant either High Definition or Hybrid Digital. Pessimists said it stood for Highly Defective.

 

[davideduardo]

My only "but" to that is that the programming is not what killed AM. The companies were still pouring money into live talent. Ultimately the sound on FM was obviously better. Plus the music was changing. and that provided the content for more stations.

And noise levels caused by everything from fluorescent bulbs to wall warts and CPUs have reduced the effective coverage areas of most AM stations by at least 50% if not more.

 

[davideduardo]

Do you happen to know the efficiency ranges that were common with the original generations of tube transmitters like the gigantic RCA 50A and 50B? I had a look through a few historical pages on them but other than mentions of individual tube characteristics, I saw nothing about total kW in versus total kW out.

Obviously it varied by brand. An Ampliphase had different efficiencies than a high level plate modulated rig.

I am guessing, based on decades of building, installing and maintaining 1 kw to 10 kw AMs in the 60's and 70's that all are in the 40% to 60% efficiency range.

Radio's pioneers choosing the term carrier always perplexed me because the carrier doesn't literally carry (in the sense of conveying) the audio. Maybe it's a chicken vs. egg thing, but it's the act of rapidly changing (distorting) a carrier's amplitude or frequency that generates the sum and difference frequency products that are the upper and lower sidebands that in turn are the spectral clones of the audio that dictated those very changes to its amplitude/frequency in the first place. Suppress that carrier afterward and you still have your audio as DSSC, or USB/LSB if you also remove a sideband. Somehow it would have made more sense had they called carriers pilots -- the same as they did with FM's DSSC stereo's carrier after halving its frequency to 19 kHz.

But the fact is that, until we got into hybrid systems in the late 70's, a typical AM rig had an oscillator and RF driver system and an audio amplification system. A typical 1 kw rig had 2 4-400A audio tubes in push-pull and two RF tubes of the same kind to create 1kw of carrier.

So put the RF driver and audio stage at about 300 watts, including heat, and the fans at about 600 watts and the tubes at their rated efficiency and you have about 2,400 watts consumption if the station was using fairly decent audio processing.

What many don't "get" is that the transmitter site might use over twice the transmitter power consumption in heating or cooling, exhaust fans, tower lighting, the equipment rack with remote control, whatever STL system was used, a peak limiter and such. Many of us had voltage regulators that were lossy if the power line was not stable, and we had lights on the outside of the building and, sometimes, around the lot, for security. Some had a second transmitter on hot standby with filaments on at all times, ready to switch.

 

[KeithE4]

And noise levels caused by everything from fluorescent bulbs to wall warts and CPUs have reduced the effective coverage areas of most AM stations by at least 50% if not more.

Don't forget about the grounded-chicken-wire/stucco encrusted houses that have been common in many parts of the country (like mine) since the 1980s. They're a 20-40 dB attenuator, depending on frequency, from 500 kHz thru UHF that all but eliminate the use of indoor antennas. This is especially true on AM, but also affects low-powered FM and TV stations. It keeps the noise sources in and the signals out. I barely pick up any AM stations inside my house, local or distant. If I want to listen to AM, I have to take a radio outside or listen in my van.

 

[davideduardo]

Don't forget about the grounded-chicken-wire/stucco encrusted houses that have been common in many parts of the country (like mine) since the 1980s. They're a 20-40 dB attenuator, depending on frequency, from 500 kHz thru UHF that all but eliminate the use of indoor antennas. This is especially true on AM, but also affects low-powered FM and TV stations. It keeps the noise sources in and the signals out. I barely pick up any AM stations inside my house, local or distant. If I want to listen to AM, I have to take a radio outside or listen in my van.

And in some areas such as Puerto Rico, wood frame homes are not preferred and instead we have reinforced concrete walls and roofs, full of both rebar and stuff that looks like a chain link fence. That construction is the usual type in all of the tropical zones of the world.

 

[KeithE4]

And in some areas such as Puerto Rico, wood frame homes are not preferred and instead we have reinforced concrete walls and roofs, full of both rebar and stuff that looks like a chain link fence. That construction is the usual type in all of the tropical zones of the world.

Is that due to hurricanes? I can understand if that's the case. We don't have that problem in AZ, but pretty much all home construction here since the early '80s has been lath/stucco, with wood frame construction. I think it's been more for looks than anything else. I prefer the older cinder blocks myself, but they're getting harder to find these days.

 

[yeoldeschool]

The folks at ibiquty said, over 20 years ago, that "HD" did not stand for anything. People in the industry decided on their own that it meant either High Definition or Hybrid Digital. Pessimists said it stood for Highly Defective.

Knowledge that "HD" meant "high definition" was very widespread by the early 2000s because of all the prior media buzz and testing, dating as far back as 1996, of HDTV -- testing which was rapidly followed by initial deployments. iBiquity having the gall to say "HD" didn't stand for anything at such a time should've been the warning label over their faith in their product. Seriously? What a twofaced marketing maneuver -- to cast the impression of "high definition" into the consumer sphere through associative implication while leaving themselves an exit for any time an expert called them on it.

 

[CTListener]

Knowledge that "HD" meant "high definition" was very widespread by the early 2000s because of all the prior media buzz and testing, dating as far back as 1996, of HDTV -- testing which was rapidly followed by initial deployments. iBiquity having the gall to say "HD" didn't stand for anything at such a time should've been the warning label over their faith in their product. Seriously? What a twofaced marketing maneuver -- to cast the impression of "high definition" into the consumer sphere through associative implication while leaving themselves an exit for any time an expert called them on it.

I'm sure the people who needed to know that the letters didn't stand for anything -- the engineers involved in its creation and implementation, the clients who'd be paying for the technology to be installed in their radios, etc. -- knew exactly what HD Radio was and wasn't. The radio users? Let them believe what they want, so long as they buy and are satisfied with the product. Audiophiles in general are outliers. I'll bet many users of HD Radio actually believe the sound quality is "high definition" through a sort of placebo effect -- the letters "HD" convince them that the audio they'll be hearing is superior to regular FM sound before they've heard a single note. You may call iBiquity's approach two-faced or cynical. And it is, but remember, while there's a sucker born every minute, most of them are completely satisfied consumers and never know they've been suckers.

 

[Kelly A]

I'm sure the people who needed to know that the letters didn't stand for anything -- the engineers involved in its creation and implementation, the clients who'd be paying for the technology to be installed in their radios, etc. -- knew exactly what HD Radio was and wasn't. The radio users? Let them believe what they want, so long as they buy and are satisfied with the product. Audiophiles in general are outliers. I'll bet many users of HD Radio actually believe the sound quality is "high definition" through a sort of placebo effect -- the letters "HD" convince them that the audio they'll be hearing is superior to regular FM sound before they've heard a single note. You may call iBiquity's approach two-faced or cynical. And it is, but remember, while there's a sucker born every minute, most of them are completely satisfied consumers and never know they've been suckers.

For about six months I was helping an FM classical station running HD. I was rather surprised how the audiophiles in the area insisted on only listening to the HD1 because the superior frequency response, stereo image, and noise floor of the original recording. Sure, like any audio or videophile, they didn't equal a very high number, but they did frequently donate, and understood the quality difference.

 

[davideduardo]

Is that due to hurricanes?

No, it is due to climate. Even in places I have lived like Quito, Ecuador, at 10,000 feet AMSL we built with reinforced concrete or brick and mortar, not wood. Part of that is due to the distance from the northern forests that provide the kinds of wood suitable for home and building construction, but most is due to climates with no winter and warmer weather year round.

I can understand if that's the case. We don't have that problem in AZ, but pretty much all home construction here since the early '80s has been lath/stucco, with wood frame construction. I think it's been more for looks than anything else. I prefer the older cinder blocks myself, but they're getting harder to find these days.

The best construction for hot climates is block or reinforced concrete. I've lived and worked in places ranging from Mexico City to San Juan, Guayaquil, Panama City, Lima and Santo Domingo and all are most comfortable with that kind of structure. In fact, Native American construction of adobe, nature's concrete, is an adaptation of available resources to the local climate.

 

[davideduardo]

Knowledge that "HD" meant "high definition" was very widespread by the early 2000s because of all the prior media buzz and testing, dating as far back as 1996, of HDTV -- testing which was rapidly followed by initial deployments. iBiquity having the gall to say "HD" didn't stand for anything at such a time should've been the warning label over their faith in their product. Seriously? What a twofaced marketing maneuver -- to cast the impression of "high definition" into the consumer sphere through associative implication while leaving themselves an exit for any time an expert called them on it.

Ibiquity simply took a "buzz term" of "HD" and applied it to radio without applying meaning to it. The "product" had been in development by others for more than a decade and Ibiquity was formed, with broadcasters and venture capital funding, to take the concept into actual use. They saw that "HD" had been given meaning by the TV industry and grabbed it.

Most TV set purchasers simply knew that "HD" meant "better picture". So "HD" in radio was to be interpreted as "better sound".

 

[K.M. Richards]

Knowledge that "HD" meant "high definition" was very widespread by the early 2000s because of all the prior media buzz and testing, dating as far back as 1996, of HDTV -- testing which was rapidly followed by initial deployments. iBiquity having the gall to say "HD" didn't stand for anything at such a time should've been the warning label over their faith in their product. Seriously? What a twofaced marketing maneuver -- to cast the impression of "high definition" into the consumer sphere through associative implication while leaving themselves an exit for any time an expert called them on it.

You just condensed into three sentences and a rhetorical question everything I have said about iBiquity using a deliberately confusing term from the outset. They should have been legally enjoined from doing so as soon as the lack of "high definition" was exposed.

 

[Mediafrog+]

I am guessing, based on decades of building, installing and maintaining 1 kw to 10 kw AMs in the 60's and 70's that all are in the 40% to 60% efficiency range.

I was recently re-reading an old article from 1969 that described the (then new) Radio Netherlands shortwave relay station on Bonaire in the Caribbean. The facility started out with two 300kw transmitters. The article stated that each required around 900kw of power consumption.🤯

What many don't "get" is that the transmitter site might use over twice the transmitter power consumption in heating or cooling, exhaust fans, tower lighting, the equipment rack with remote control, whatever STL system was used, a peak limiter and such.

That same article said that total power consumption for the entire transmitter facility was around two megawatts.

 

[TomásEstefan]

The folks at ibiquty said, over 20 years ago, that "HD" did not stand for anything. People in the industry decided on their own that it meant either High Definition or Hybrid Digital. Pessimists said it stood for Highly Defective.

It's also been referred to as IBOC (In-band On Channel), which is misleading, it should be called IBAC: In-band Adjacent Channel, as the Ibiquity system causes catastrophic adjacent channel interference on both bands.

 

[davideduardo]

It's also been referred to as IBOC (In-band On Channel), which is misleading, it should be called IBAC: In-band Adjacent Channel, as the Ibiquity system causes catastrophic adjacent channel interference on both bands.

But the reason for stressing both "in band" and "on channel" was to distinguish HD from digital on another band (Europe mostly) or on a different frequency (DRM). That was likely important when system alternatives were still being discussed, but now that it is a fait accomplit, neither term is needed.

 

[Kelly A]

It's also been referred to as IBOC (In-band On Channel), which is misleading, it should be called IBAC: In-band Adjacent Channel, as the Ibiquity system causes catastrophic adjacent channel interference on both bands.

Blah blah blah. FM HD stations don't cause adjacent channel interference. Technically, neither do properly maintained AM HD stations. Both if inside the 'mask' are legal as defined by the Commission rules.

 

[K.M. Richards]

FM HD stations don't cause adjacent channel interference.

I'm now trying to remember what the outcome was in this complaint:

KATY-FM files FCC petition against KRTH HD Radio interference | Radio & Television Business Report

All-Pro Broadcasting, Inc., licensee of KATY-FM, 101.3 MHz, Idyllwild, California (Riverside-San Bernardino), is filing a Petition with the FCC seeking relief from ongoing and destructive interference

rbr.com