Some clear thinking on IBOC: Skotdal: AM Band Needs Drastic Change

[KB1OKL]

The AM BCB band doesn't need anything drastic, it needs part 15 rules to be enforced, it needs better receivers and it need transmitters to be transmit up to about 10-12 kHz wide, that's it.

 

[TheBigA]

The AM BCB band doesn't need anything drastic,

...It needs listeners.

 

[davideduardo]

The AM BCB band doesn't need anything drastic, it needs part 15 rules to be enforced, it needs better receivers and it need transmitters to be transmit up to about 10-12 kHz wide, that's it.

Those horses left the barn. Consumers are not buying stand-alone radios today. Any improvements would have to be incorporated in multifunction devices, such as the entertainment centers in vehicles and in smartphones.

Since smartphones are likely never to have AM incorporated, why not direct the effort at improving the streaming of local AMs so that consumers who consider their smartphone to also be a "radio" can hear the programming without poorly done commercial substitution and dead air and such.

For cars, considering that the average vehicle is nearly 11 years old, it would take a decade to just get better radios in half the cars in the US. AM OTA radio does not have that big a "survival opportunity".

Your suggestion ignores the continuously growing man-made noise level on AM as well as the fact that few metro area AMs cover their own market day and night.

 

[tomservo]

The AM BCB band doesn't need anything drastic, it needs part 15 rules to be enforced, it needs better receivers and it need transmitters to be transmit up to about 10-12 kHz wide, that's it.

Yes, nothing drastic... Just the compete reworking of the entire system from one end to the other. *rolls eyes*

 

[JoshTheRadioDude]

Trying to fix AM at this point is like trying to make the 707 a popular airliner again. It's outdated, too small and filled with too many occupants, economically wasteful, and nobody wants it anymore.

 

[TheBigA]

Trying to fix AM at this point is like trying to make the 707 a popular airliner again. It's outdated, too small and filled with too many occupants, economically wasteful, and nobody wants it anymore.

It depends. Air Force One is a variant of the 707. In fact, lots of private planes are similar to the 707. That's what AM is doing. Adapting to the needs of certain fringe audiences who are looking for this kind of media. Yes there are lots of problems, and yes the FCC caused a lot of them, and no the FCC isn't going to fix it. AM radio will probably never return to the dominance it enjoyed in the first half of the 20th century. But to say "nobody wants it anymore" ignores the people who enjoy it every day.

 

[JoshTheRadioDude]

Nope, the 707 AF1's haven't flown since 1990. They're reconfigured 747's now. And they're actually looking at replacements for 2017 at the moment.

Relating that to AM, even the fringe isn't looking for what they want on AM, they're going online. It's much easier to find what you want to hear online than it is to find that one station that caters to you in your market -- IF that station even exists (and with niche formats, that's highly unlikely, because they're just not profitable on a local basis). AM is dead. Just as dead as the 707. Yeah, there are still a few flying around out there (ten if you ask Wikipedia), only five of them are still in commercial service by two small airlines in Iran and the Democratic Republic of the Congo, two are used as VIP planes by a private airline in Iran, and the remaining three are owned by individuals, one of whom being John Travolta. The rest are either used as display models or have been bought up for spare parts. AM is just now starting to face the same fate.

 

[TheBigA]

Relating that to AM, even the fringe isn't looking for what they want on AM, they're going online.

Some are, some aren't. Internet radio isn't as easy as AM or FM. That's one of the biggest problems it faces. Too many stations, too hard to find exactly what you want, you need some form of connectivity, and when you're talking about the 17% of the people who use AM, a lot of them simply don't have the internet or a smart phone. Don't misinterpret this as there's a great AM revival coming. I'm not saying that at all. But there is a use for it, just as there's a use for anything else you might say is obsolete. And when people can't make a living with it anymore, they'll stop using it.

 

[pianoplayer88key]

I use internet radio, but I also am a fan of AM and I'm young enough to be many of you DXers' grandson or great grandson. (I'm only 33.)

I'd love for internet / digital radio to improve, but some things need to change, one of them being eliminate the compression artifacts.

Another (more important to me I think) thing would be cost for the service - getting on the internet requires a paid subscription usually. That's one reason I'm personally quite ready for internet radio to replace OTA. For OTA radio, just a $15 radio (Sony SRF-59), and a $20 or $30 or so charger & battery setup (Sanyo/Panasonic Eneloop - maybe even a solar / windup charger but idk the prices on those) and you have years of radio listening for free after that initial purchase. In contrast, until just this last month my unlimited everything (including data) data cell phone plan was $70/month plus taxes, fees, etc. (I just switched to a $30/month 5GB (+ 100 minutes & unlimited messages and throttled data over the 5gb soft cap) plan which I think has no extra fees tacked on.)

 

[davideduardo]

Trying to fix AM at this point is like trying to make the 707 a popular airliner again. It's outdated, too small and filled with too many occupants, economically wasteful, and nobody wants it anymore.

Tell that to groups like Salem, IHR, Multicultural, Lotus and others who have found out how to have successful AMs and are buying more.

 

[Kelly A]

Take it off both. It severely affects coverage and building penetration. Nobody but me would notice it is gone from FM.

IBOC/HD sub-carriers on FM has no bearing on building signal penetration or field strength. You've made that statement before Bruce, but it's entirely incorrect.

 

[rbrucecarter5]

IBOC/HD sub-carriers on FM has no bearing on building signal penetration or field strength. You've made that statement before Bruce, but it's entirely incorrect.

What experiments have you performed to make that statement? I have conducted careful scientific experiments with Agilent test gear, and my results are pretty clear - HD hobbles coverage. I am not bought and paid for by the HD cartel, so I can tell the truth about the technical shortcomings of the system.

 

[JoshTheRadioDude]

Any time you reduce useable analog audio power in favor of other purposes (stereo, SCA, IB(A)C, et cetera), you reduce signal strength of that useable analog audio. Simply measuring the strength of a station that switches between monaural and stereo audio proves that. IB(A)C is no different. So yes, it does indeed diminish coverage and penetration into buildings. That's scientific fact. Any engineer worth their salt will tell you the same.

 

[davideduardo]

Any time you reduce useable analog audio power in favor of other purposes (stereo, SCA, IB(A)C, et cetera), you reduce signal strength of that useable analog audio. Simply measuring the strength of a station that switches between monaural and stereo audio proves that. IB(A)C is no different. So yes, it does indeed diminish coverage and penetration into buildings. That's scientific fact. Any engineer worth their salt will tell you the same.

HD (IBOC) "power" is produced by a separate transmitter or module in an analog transmitter and, viewed simplistically, diplexed into the same antenna. The analog power is unchanged, with or without the HD transmitter operating.

In fact, in some cases the HD signal is transmitted via a separate antenna. While I am uncertain of the present state, when HD began on the stations using the John Hancock site in Chicago, a separate antenna was used for HD operations.

 

[JoshTheRadioDude]

You still have to fit the same bandwidth and transmit with the same total ERP. That means that you're reducing the power of the analog audio for the HD subcarrier. Separate transmitter and/or antenna or not, it doesn't matter. You're still reducing power on useable analog audio.

 

[Kelly A]

HD (IBOC) "power" is produced by a separate transmitter or module in an analog transmitter and, viewed simplistically, diplexed into the same antenna. The analog power is unchanged, with or without the HD transmitter operating.

In fact, in some cases the HD signal is transmitted via a separate antenna. While I am uncertain of the present state, when HD began on the stations using the John Hancock site in Chicago, a separate antenna was used for HD operations.

David is correct. The HD sidebands have absolutely no effect on the analog (stereo or mono) carrier or the field strength therein. They are sidebands created by either a separate transmitter and inserted into the same or an alternate antenna. In fact, the commission requires that the analog carrier power and ERP is not altered from the licensed parameters, HD or no. As far as your comment Josh about analog FM sidebands reducing coverage or field strength of an FM carrier, that is completely incorrect. And I have plenty of "salt" thank you, having been a broadcast engineer with major radio and TV groups for over 30 years. Don't care for the concept of HD radio? No problem. Just don't make up technical reasons that are complete BS.

 

[JoshTheRadioDude]

David is correct. The HD sidebands have absolutely no effect on the analog (stereo or mono) carrier or the field strength therein. They are sidebands created by either a separate transmitter and inserted into the same or an alternate antenna. In fact, the commission requires that the analog carrier power and ERP is not altered from the licensed parameters, HD or no. As far as your comment Josh about analog FM sidebands reducing coverage or field strength of an FM carrier, that is completely incorrect. And I have plenty of "salt" thank you, having been a broadcast engineer with major radio and TV groups for over 30 years. Don't care for the concept of HD radio? No problem. Just don't make up technical reasons that are complete BS.

Sure you are. And I'm Mickey Mouse. You cannot add modulation within the same bandwidth and power restrictions. It's not physically possible. Something has to give, either bandwidth or power, and in IB(A)C's case, it's power. This is easily demonstrated. You're an apologist for the technology? No problem. Just don't pretend that you actually know what you're talking about, because you've just proven that you don't.

 

[Kelly A]

I can tell you're one of these insecure posters who, if not able to make their incorrect point, resort to snarky comments and eventually name calling. I encourage you to review the vast amount of websites who can explain how FM modulation, and in particular for broadcast functions.

Going back to the topic at hand; say a station with a licensed analog TPO of 7kW, running IBOC at -20dB using common amplification with a solid-state transmitter capable of 8kW combined power, would be able to increase IBOC injection to -10dB by adding a second matching amplifier and a 3dB combiner for a maximum combined TPO of 8.5kW and an analog maximum of 7.6kW. At -14dB, an analog TPO of 10kW is possible. For a station with a licensed analog TPO of 20kW running -20dB of common amplification with a tube transmitter, adding a matching second amplifier through a 3dB combiner would only deliver a maximum analog power of 16.4kW. This would not enable the station to achieve -10dB at full power. At -12dB however, this configuration would be capable of about 23kW of analog power. The Commission allows for a total IBOC increase of -10dB(c) for FM.

In response to Bruce's question about how one would measure field strength using Agilent-brand test gear, you couldn't. Agilent makes fine RF spectrum and network analyzers, neither of which would produce an accurate measurement of field strength, especially inside a structure. Typically the industry relies on instruments such as FM field strength meters such as a Potomac Instruments FIM 71, with a known antenna gain calibrated to the meter, to measure field strength.

 

[davideduardo]

Sure you are. And I'm Mickey Mouse. You cannot add modulation within the same bandwidth and power restrictions. It's not physically possible. Something has to give, either bandwidth or power, and in IB(A)C's case, it's power. This is easily demonstrated. You're an apologist for the technology? No problem. Just don't pretend that you actually know what you're talking about, because you've just proven that you don't.

For starters, you are totally forgetting that in HD you are simultaneously transmitting an analog signal and a digital one in the same sliver of the spectrum. Digital does not subtract from analog and analog does not have to be reduced to meet the TPO specified in the license.

Kelly A is obviously a competent broadcast engineer with years of experience. The fact that he has told you that you are wrong is not a reason to start insulting him: it is reason for you to consider whether you ought to read up a bit more before engaging in technical arguments with experts. Oh, and following up on Kelly's "salt" comment... in my late teens and 20's I built more than a dozen broadcast transmitters, both AM and FM, from scratch including FM exciters and stereo generators and even the FM antenna elements.

 

[tomservo]

I'm not an engineer so my opinion is worthless, but I can say as an observant listener in a market where all the class C stations share two common transmitter sites and some run HD and some don't, there's zero noticeable difference between the ones in HD and the ones who aren't. One of the stations runs higher HD power and it also hasn't lost any coverage.

I live in an area where any loss of coverage would be detrimental. Mobile and Pensacola are two different markets and the shared sites are halfway between each market. So each big signal has 20+ miles to go before reaching the population centers.

Granted, the HD signals are almost totally useless except the high power broadcasters... But the analog signals are just fine. Not too long ago I was in the Gulf Breeze Walmart and all the stereos were tuned to WBLX. Cheap Chinese crap radios, in a big metal building, over 40 miles from the TX site, the HD signal definitely is not impeding that signal or its double digits showing each quarter in the ratings.