How is IBOC destroying AM DX?

[louisNatl]

I enjoy listening to AM distant signals. As a fan of talk radio, we only have one full time talk radio station in Atlanta (WSB) and the others reduce their power so low at night that the signal is not received in most of the area. So, I rely on distant signals for my favorite programs such as Coast To Coast. I also enjoy HD FM radio because of the good quality sound. I have never heard HD AM because the two rimshot stations here stopped broadcasting. However, every review that I have read about it give it high marks as potential for music and higher quality programming to return to AM. Since AM stations are allowed to broadcast at night, I have not noticed any degrading of the distant signals that I normally receive (WHAS, WLAC, KMOX, etc.). I have noticed that WLS is barely audible but that seems to be due to interference with a Mexican station.

I decided to post here because the HD Radio board is filled with members stating their personal biases against the technology rather than documenting physics or any actual proof of interference. I would like to know if someone actually has documented findings that HD radio interferes with adjacent frequencies. I would think that the HD technology would make the 50,000 clear channel stations even stronger at night but I am not a physics expert.

 

[BobOnTheJob]

I would think that the HD technology would make the 50,000 clear channel stations even stronger at night but I am not a physics expert.

Let's look at how IBOC works...it transmits it's AM component on neighboring frequencies. It's at relatively low power, but relatively low power compared to 50,000 watts is still a thousand watts or more. Take WLW and WOR for example. Unless the rules have been relaxed, there are no nightime signals on either of those frequencies within 750 miles at any power. In the FCC eyes, even a couple of watts on 700khz at 500 miles would create unacceptable interference. Why, then, do they allow 1000 watts on 700 from WOR????

As far as a documented case of interference, I live 80 miles from WHAS 840. A few months ago, someone had their IBOC turned on on 850 a couple of hours before sunrise. I never was able to identify who it was as the IBOC hiss was more audible on 840 & 860 than the jumble of analog signals on 850. At 80 miles, it did not make WHAS unlistenable, but it did add enough hiss to it that I thought I was listening to a very weak signal...until I investigated & found out that IBOC was the source. That's 1 IBOC signal...imagine what happens to WHAS 840 when WCCO 830 & KOA 850 BOTH start adding their hiss generators to the mix. If every station were to embrace IBOC on AM at night, it's my opinion that the perception of AM radio being "full of noise & static" will be greatly reinforced. The FCC staff who allowed this should all be removed from office & replaced with passionate terrestrial radio users. I could be wrong, but I wouldn't be surprised to find that these commissioners get in their Cadillacs & turn on XM when they leave work...

 

[louisNatl]

That's a good explanation. Is there any way that the AM stations can transmit IBOC without leaking on to adjacent frequencies? Otherwise, wouldn't this violate FCC rules since stations like WHAS are guaranteed large contours? Apparently, there was a white paper (sorry, I don't have the source) that explained how IBOC was engineered on FM to not interfere with adjacent channels but did not mention AM.

 

[BobOnTheJob]

It trashes FM too and it's easy to see if you have an analog tuner with a tuning meter. Say you have a local station on 106.9. Tune your receiver to 107.1 and 106.7. The signal meter should drop to almost zero with no IBOC. Depending on your distance from the local station, you'll see anywhere from a small reading to almost full signal on the meter. There are many tuners capable of selecting an adjacent channel with little or no interference. The McIntosh MR-78 is an example. The signals that were once on the adjacent channels are now buried in hiss. For whatever reason, everyone talks about the guaranteed AM carnage, but little mention is made to the FM band.

Example...96.7/Madison,IN formerly was crystal clear on I-275 in northern KY. When 96.5/Lebanon,OH signed on with IBOC, 96.7 went from a listenable signal to 100% hiss at less than 40 miles. Their stereo signal at 24 miles now has hiss in it that will force listeners to switch to mono if they know to, know how or are able to. In the real world, Madison on 96.7 will lose a listener each time this happens, making the station less valuable. And they call this progress...

 

[PocketRadio]

“The FCC Tunes Into HD Radio–And May Turn Off Distant AM”

http://blog.washingtonpost.com/fasterforward/2007/03/the_fcc_greenlights_hd_radio_n.html

“RW Opinion: Rethinking AM’s future”

“Making AM-HD work well as a long-term investment is seen as an expensive and risky challenge for most stations and their owners. There is the significant downside of potential new interference to some of their own AM analog listeners as well as listeners of adjacent-channel stations.”

http://www.rwonline.com/pages/s.0044/t.557.html

 

[rbrucecarter5]

I would like to know if someone actually has documented findings that HD radio interferes with adjacent frequencies. I would think that the HD technology would make the 50,000 clear channel stations even stronger at night but I am not a physics expert.

Happy to oblige!

Since AM is still not authorized for nighttime operation, daytime is the only example of interference except for those occasions when it was being tested at night, or somebody got careless.

Case 1: KKLF 1700 interferes with local TIS station on 1680 from DFW airport, making it difficult for airport travellers to get gate information.
Case 2: KLIF 570 interferes with KLBJ 590 Austin in the Dallas / Ft. Worth area. KLBJ is a blowtorch, giving local signal quality in the DFW area.
Case 3: WOAI 1200 interferes with KFXR 1190 Dallas near sunrise and sunset - producing an audible increase in noise.
Case 4: KLIF 570 sidebands produce noticable noise on KLVI 560 in Houston. KLVI, although licensed to Beaumont, is listed as a Houston local and shows up in their ratings. KLIF noise is especially strong in northern suburban areas of the Woodlands and Conroe.

In spite of reduced power on the sidebands, the nature of the modulation makes them much more robust than the analog signal. Just as the carrier is much more robust than modulation (transatlantic heterodynes are relatively common, while actual reception rare). In careful DX tests I have performed, I have received digital sideband pairs from stations so distant that the analog modulation is not even detectable. Sidebands from stations like KOA, KMKI, WOAI are clearly audible 300 miles from the station, obliterating semi-locals even 300 miles away (a 630 in Lovington, NM is no longer receivable in Lubbock, an 860 from Hereford is no longer audible in Dumas to Amarillo on US 87.)

All in all, I would say that the situation before was one where the first adjacent is difficult to listen to when a station runs 10 kHz bandwidth audio. But that would make the effective bandwidth only +/-30 kHz under worst case circumstances. And - outside of the city grade signal contours, the extended frequency response seldom caused any problems, because most musical and speech energy is below 5 khz anyway. When a station goes IBOC, the 5 to 10 kHz sidebands are equal in amplitude and translated down to 0 to 5 kHz on the first adjacent frequency. On the second adjacent frequency, they mix with the 10 to 15 kHz sidebands to create primarily high frequency hiss from 5 to 15 kHz. First and second adjacents are VERY unpleasant to listen to!!! Much, but not all, of the second adjacent hiss can be mitigated with an extremely narrow IF - the type that used to be common in AM radios before the advent of single IC / single ceramic filter designs.

More recent AM radio designs use a single, really cheap ceramic filter which does not have much stop band rejection. Therefore, the radio is wideband by its nature and the 10 to 15 kHz sidebands are clearly audible even if the radio is tuned carefully to center frequency. Even a little off frequency, that the phase modulated 5 to 10 kHz sidebands become amplitude modulation and their contribution to the audio is considerable. Given poor mechanical design and poor mechanical lash of most tuning mechanisms, the average listener will be subjected to this noise.

 

[davideduardo]

Case 4: KLIF 570 sidebands produce noticable noise on KLVI 560 in Houston. KLVI, although licensed to Beaumont, is listed as a Houston local and shows up in their ratings. KLIF noise is especially strong in northern suburban areas of the Woodlands and Conroe.

KLVI is listed by who as a Houston local? Not by Arbitron, particularly since KLVI does not show up in the Houston ratings... and I just checked the last 5 weeks of PPM to be sure.

 

[davideduardo]

Case 4: KLIF 570 sidebands produce noticable noise on KLVI 560 in Houston. KLVI, although licensed to Beaumont, is listed as a Houston local and shows up in their ratings. KLIF noise is especially strong in northern suburban areas of the Woodlands and Conroe.

KLVI is listed by who as a Houston local? Not by Arbitron, particularly since KLVI does not show up in the Houston ratings... and I just checked the last 5 weeks of PPM to be sure.

And...

..in the event someone says, "well, sure, that's because HD makes that impossible," I went back several years and see that KLVI gets a share of 0.0 all through 2005 in the Houston MSA... and considering that Liberty and Chambers counties are in the HOuston Arbitron market, that means that even in counties adjacent to the home market for KLVI, nobody was listening anyway.

 

[MarcB]

Case 1: KKLF 1700 interferes with local TIS station on 1680 from DFW airport, making it difficult for airport travellers to get gate information.

Are you kidding me? How many people actually use that? I'll bet slim to none. Further more I have friends of all ages from my age (25) all the way up to people in their 60s and none listen to those T.I.S. stations that are on the highways to announce where construction zone/accidents are. Most of them will use the traffic reports from their favorite radio stations. A ver small percentage don't care about traffic conditions.

 

[4dude]

IBOC is devistating to the AM band!!!

The other night some station around 910 left thier IBOC up all night and all i heard was hash mixed in with the stations (I couldnt make anything out)

 

[louisNatl]

So if I am understanding you correctly, there are methods that the broadcaster can take to reduce the sideband noise. It makes sense that it can not be eliminated because it seems that there is bleedover on adjacent frequencies of a strong station regardless if they are broadcasting in HD. I live about 10 miles from the blowtorch of WSB 750 AM here in Atlanta. On some of my older radios and on my BA Receptor HD, I receive a bleedover of the WSB broadcast on 740 and 760 AM both day and night. However, my Sangean RCR-2 alarm clock radio does not exhibit this behavior. I can reliably receive a signal on 760 which broadcasts from Detriot and on certain nights I can receive a signal on 740 that I think originates from Houston but it's hard to make out as it fades often. I will say that I have not heard any hiss or indication of a signal noise on the FM band adjacent frequencies on my Receptor. I will admit that I may not know what to listen for but in all honesty, I do not hear anything different or unusual on those frequencies and I've also asked friends to listen as well.

I thought that the FCC allowed AM stations to broadcast IBOC 24-hours starting about a month ago. I don't know if this will benefit the 50,000 watt clear channel stations that broadcast HD at night, but again I have not noticed a difference either way.

rbrucecarter, you mention KLIF. According to Radio-Locator, they seem to have strong coverage especially in the daytime for just a 5,000 watt signal. Does IBOC have anything to do with that? If so, I can see IBOC as being more of a trade off. The strong stations become stronger at the expense of weaker ones.

PocketRadio, those links that you provided actually provide a convincing case in favor of HD Radio, especially if you read the comments at the end. It makes you consider the business side of it. There is a surplus of AM radio stations, many of them unsuccessful. The AM band in its present state may not be able to withstand new technology such as iPods, streaming radio, TV, and on demand content.

Also, the younger generation (Gen X) grew up listening to FM and the next generation (Generation Y) listens to CDs, iPods, and on demand content to fit their ADD personalities. I am part of Generation Y (just barely since I was born in 1977), but I grew up listening to talk radio because I found it more stimulating and thought provoking than repetitive music. I value the fact that my radio can receive numerous signals from all over the country at night when I usually listen.

However, as noted in the article (thanks to PocketRadio), advertisers do not care that the station's signal can be received up to 500 miles away thanks to tropo/skip conditions. As long as the signal covers the market equivalent to an FM signal they don't care. Besides, I can not really support a car dealer that I heard advertised on WHAS since I live in Atlanta. Also, as much as I enjoy the novelty of DXing, it does not make a very big impact on the station. The proof is that distant stations do not show up in the books in other markets. The exception to this may be WWL in New Orleans which appears in the Jackson, MS and Gulf Coast books where it actually beat the local talk station in the Biloxi market. I am sure this is partially due to the many displaced Katrina refugees in these regions though. Honestly, these stations don't care about reaching distant locations as long as they are doing well and covering their local markets.

From a business perspective, this change may be inevitable in order for AM to gain listeners from younger generations. However, stations should make sure that there signals do not damage reception of other stations.

As an aside, did AM Stereo cause similar problems? I am not very familiar with it but I remember hearing about it when I was a child.

 

[louisNatl]

IBOC is devistating to the AM band!!!

The other night some station around 910 left thier IBOC up all night and all i heard was hash mixed in with the stations (I couldnt make anything out)

I am curious to know what this sounds like since there are no IBOC AM stations in my area. Can you get a recording or do you know if someone has posted one?

 

[4dude]

It sounds like noise covering the frequency,its disgusting!!!!!!

I dunno if someone can upload a clip for you to hear or not... (I dont have any)

 

[davideduardo]

So if I am understanding you correctly, there are methods that the broadcaster can take to reduce the sideband noise.

Not really. The system behind HD puts energy in the sidebands, in a specific manner.

I thought that the FCC allowed AM stations to broadcast IBOC 24-hours starting about a month ago.

The FCC approved, but the rules have not yet appeared in the Federal Register to make them official.

The strong stations become stronger at the expense of weaker ones.

IBOC does not change the signal strength one way or another for all practical purposes.

The AM band in its present state may not be able to withstand new technology such as iPods, streaming radio, TV, and on demand content.

AM is pretty dead already. Most of the listeners are over 45 or 50.

However, as noted in the article (thanks to PocketRadio), advertisers do not care that the station's signal can be received up to 500 miles away thanks to tropo/skip conditions. As long as the signal covers the market equivalent to an FM signal they don't care.

That is because radio is bought by the market, using local stations. There is, and has not been since the late r40's, a model for buying distant markets via AM skip... because nearly all radio listening and ad placement takes place in the daytime, not at night when there is nearly no listening to AM.

The proof is that distant stations do not show up in the books in other markets. The exception to this may be WWL in New Orleans which appears in the Jackson, MS and Gulf Coast books where it actually beat the local talk station in the Biloxi market.

WWL does not appear in the Jackson book... it showed once during Katrina, and that is the only time I can find in the last 10 years. The local Biloxi FM talker, WBUV, kills WWL in the Biloxi-Gulfport-Pascagoula book. WWL appears in markets where there is a groundwave day signal, and gets very little out of market listening at night.

I am sure this is partially due to the many displaced Katrina refugees in these regions though.

Refugees don't get Arbitron diaies. The listening in some distant markets that happend in the period when Katrina hit was done by local residents wanting direct storm reports.

As an aside, did AM Stereo cause similar problems? I am not very familiar with it but I remember hearing about it when I was a child.

AM stereo was analog, and too little to late, thanks to leonard Kahn.

 

[dx7]

David Eduardo wrote:

"AM is pretty dead already. Most of the listeners are over 45 or 50."

My response:

So being over "45 or 50" is what killed AM radio? What a crock.

There are still TENS OF MILLIONS of radio listeners over "45 or 50", David, and you know what? A lot of them have lots of MONEY...and actually BUY THINGS with it.

The hometown AM I own sure doesn't seem dead to me OR my listeners. In fact, I don't give a rat's a_ _ that most of my listeners are over "45 or 50". We have a higher cume in our county than all the blowtorch big market FMs in the neighboring county have here. And we are making money.

The future? No one knows what the future will bring for AM OR FM. But once I'm gone, I bet someone else will figure out how to keep our little AM a part of the community.

I also have heard that, just in Texas alone, those "dead AMs" like KTRH, WBAP, WOAI, KLBJ-AM, KLVI and a lot more like them actually HAVE LISTENERS and are actually MAKING A LOT OF MONEY.

Please stop generalizing about AM radio being dead -- it may be dead in your hometown, but it's not dead everywhere. And stop assuming people who are "over 45 or 50" have one foot in the grave.

 

[davideduardo]

So being over "45 or 50" is what killed AM radio? What a crock.

No, sounding like AM is what killed AM. As each 18 months goes by, the average age of AM listeners increases by a year in rated markets. At some point, such a big percentage will be out of the sales demos that those stations in agency driven markets will not be viable any longer. This is why, to cite some examples, Clear Channel has put traditional news / talk on FMs in markets like Charleston, SC, Biloxi, MS, Pittsburgh, New Orleans, Tallahassee, etc.... to get sales demos, specifically 35-54, on news / talk, the format has to migrate to FM. Once AMs main audience-getter finds an FM home in multiple markets... there will be even less audience on AM.

There are still TENS OF MILLIONS of radio listeners over "45 or 50", David, and you know what? A lot of them have lots of MONEY...and actually BUY THINGS with it.

That is not my point... my issue is that most AM listeners are over 55, unsalable in rated markets, and very few are under 45. In fact, AM listening overall is only 19% of the total listening for radio, and under 55, AM has less than a 10 share. And that is today,

The hometown AM I own sure doesn't seem dead to me OR my listeners. In fact, I don't give a rat's a_ _ that most of my listeners are over "45 or 50". We have a higher cume in our county than all the blowtorch big market FMs in the neighboring county have here. And we are making money.

Good. I hope you save some of it. The fact is that as time moves on, less and less listening is to AM because our younger two generations have not grown up with it, and the youngest of the two expects a quality AM can not give (unless HD is successful beyond everyone's wildest dreams)

I also have heard that, just in Texas alone, those "dead AMs" like KTRH, WBAP, WOAI, KLBJ-AM, KLVI and a lot more like them actually HAVE LISTENERS and are actually MAKING A LOT OF MONEY.

And every one of them except KLBJ has an audience that is growing older each year, and revenues that are stagnant or declining in markets that are growing. KLBJ is growing a tiny amount, mostly because the market has grown enormously in revenue... over 25% in just 6 years. Yet KLBJ is only up about 10% in the same period.

Please stop generalizing about AM radio being dead -- it may be dead in your hometown, but it's not dead everywhere. And stop assuming people who are "over 45 or 50" have one foot in the grave.

I said "pretty much dead" and the exceptions are some smaller markets and the very few huge signal major market AMs. The rest are dead.

AM truly is dead or dying. That is why operators like Bonneville have moved WTOP to FM in DC, KTAR to FM in Phoenix and started simulcasting to move (like rent to own) its flagship KSL in Salt Lake.

 

[louisNatl]

I understand David's points. I do not know anyone anywhere near my age bracket that listens to AM. Yes there are some AM stations that achieve high ratings and those are the big 50,000 watt signals in the big cities. Even those stations serve an older audience than their FM counterparts. Most younger people will not consider AM because of the inferior sound quality (compared to FM) and potential interference especially when driving. Also, AM does not appeal to the growing segment of minorities because much of it is conservative talk radio. However, talk radio has saved AM and gave it a second life. As more talk and sports stations move to FM, who knows what could be the next savior of the AM band...IBOC, maybe? And, as the AM listening audience continues to age, listening on AM will continue to decline and more stations will become less significant and some will go dark.

Here are some examples. Here in Atlanta, WSB consistently earns the highest ratings in the market. However there are several small AM stations that are leased for religious and ethnic programming and some have gone silent. Just read through the borads on this site and you will find similar situations with the AM band in other markets as well. Also, WWL in New Orleans decided to simulcast their signal on FM due to the positive feedback that they received after Katrina. Despite the fact that Entercom attempted to bring in a classic hits format, the listeners wanted a simulcast of a station that they could easily receive on 870 AM. Entercom has stated that it is gained new listeners with the signal.

I enjoy AM too, but to say that AM is not declining, you would have to be in serious denial. Show me one market where the majority of top rated stations are AM.

 

[mimo]

I am 31 years old...I grew up with AM in Canada...as did most people my age. I have many friends who are under 30 who said IF a station on AM offered what they want to hear and an FM station offered the same programming, they'd listen to both stations, regardless of band, as long as it is what they wanted to hear. Many people under 45 would IF they were given the choice and the station was well programmed. I know teenagers who listen to out of market AM stations just to hear something that's not available locally. Example, coast to coast am..nearest affiliate is 2 hours away. AM isn't what it was, but it will always attract new listeners, some out of curiosity, others will grow out of FM, If I could hear an Alternative rocker on AM, I'd listen, along with the local alternative FM. I'm annoyed when people say there is no future for AM, it will always find a way to re-invent itself...it's always done so, from the 1950's to the present time. Even with the so called "noise level" I find much more interferes or hurts an FM signal than AM, I talked to a friend of mine over the french news talk AM moving to FM here, the new FM signal doesn't cover the metro area, it starts dropping out once you get 5 miles from downtown, and is gone when you drive 15 minutes out of town, All I know is there are going to be a TON of french hockey fans here in Ottawa who are going to be VERY upset when they find they won't be able to hear their games after they switch off the AM transmitter this fall.

 

[PocketRadio]

Also, WWL in New Orleans decided to simulcast their signal on FM due to the positive feedback that they received after Katrina.

KSL SLC tried simulcasting on FM, but eventually the ratings fell back to where there were, before - the problerm is that broadcast radio is in a decline, due to Satellite Radio, cell phones, iPods, gaming-systems, the Internet, etc., so nothing is going to save broadcast radio. AM-HD will just hasten the destruction of the AM band, because of adjacent-channel interference and consumers do not care about sound quality for news/talk/sports. Looks like HD is DOA, anyway.

 

[PocketRadio]

I am 31 years old...I grew up with AM in Canada...as did most people my age. I have many friends who are under 30 who said IF a station on AM offered what they want to hear and an FM station offered the same programming, they'd listen to both stations, regardless of band, as long as it is what they wanted to hear. Many people under 45 would IF they were given the choice and the station was well programmed. I know teenagers who listen to out of market AM stations just to hear something that's not available locally. Example, coast to coast am..nearest affiliate is 2 hours away. AM isn't what it was, but it will always attract new listeners, some out of curiosity, others will grow out of FM, If I could hear an Alternative rocker on AM, I'd listen, along with the local alternative FM. I'm annoyed when people say there is no future for AM, it will always find a way to re-invent itself...it's always done so, from the 1950's to the present time. Even with the so called "noise level" I find much more interferes or hurts an FM signal than AM, I talked to a friend of mine over the french news talk AM moving to FM here, the new FM signal doesn't cover the metro area, it starts dropping out once you get 5 miles from downtown, and is gone when you drive 15 minutes out of town, All I know is there are going to be a TON of french hockey fans here in Ottawa who are going to be VERY upset when they find they won't be able to hear their games after they switch off the AM transmitter this fall.

I am not going to worry about the 50KW AMs going dark anytime soon - this is just a sampling of 50KW AM stations either ranked #1, or in the top-5 (there are plenty others):

WHO-AM News Talk Information 9.7 7.2 9.9 10.6
WLW-AM News Talk Information 8.9 9.9 11.2 9.8
WSB-AM News Talk Information 9.3 8.7 9.2 8.2
WGN-AM News Talk Information 5.3 5.5 5.8 5.4
WBBM-AM All News 4.2 4.1 4.4 4.6
WLS-AM News Talk Information 4.1 3.7 3.7 3.8
WTAM-AM News Talk Information 7.3 8.0 6.5 7.3
WJR-AM News Talk Information 4.8 4.9 5.3 5.3
KMOX-AM News Talk Information 8.4 7.7 8.2 8.4
KSL-AM News Talk Information 5.9 6.7 8.6 7.7

http://www.arbitron.com/radio_stations/home.htm

The real problem is that AM-HD is in effect turning AMs into local FMs. HD/IBOC will be the destuction of the broadcast bands, especiially AM.