I got an e-mail from a friend who lives in the suburbs of Boston (about 20 miles out). He was complaining that very late at night the CBS news on the hour on WBZ (1030) was being interfered with by another CBS news on the hour. We tracked it down and got the ID as KDKA (1020). Now as far as I know both WBZ and KDKA run full time IBOC. With the IBOC sub bands splattering the way they do, unless KDKA and WBZ both turn their IBOC off at night, how this is really possible.
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IBOC Co-Channel Observation
- Thread starter K6JHU
- Start date
CBS owns 1010, 1020 and 1030; all 50kw (analog) and 500 watts HD. There is only one way to modulate a MW QAM scheme with a practical, robust result. Unlike DTV, IBOC is doing it correctly. CBS has been doing some intensive IBOC testing with all 3 of the above stations. I live around 50 miles from WBZ and can get a clean WHO 1040 -- during certain aspects of their tests -- with WBZ running IBOC. At the same time, KDKA and WBZ clobber each other with their IBOC signals while 1010 WINS is also unaffected. They have the versatility to do the opposite or run both IBOC sidebands also. There is extensive MW IBOC testing going on and lots of brain power being spent by the DSP wonks to maximize IBOC performance for the MW band.
When they FINALLY flip some of the AM dogs to FULL IBOC and allow people to hear the difference between pure digital and hybrid IBOC or analog: THEN everybody will STFU and sit down! Watch!
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When they FINALLY flip some of the AM dogs to FULL IBOC and allow people to hear the difference between pure digital and hybrid IBOC or analog: THEN everybody will STFU and sit down! Watch!
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You mean he was hearing both stations at the same time? Its possible on an analog tuning dial radio especially if it has a wide bandwidth and he wasn't tuned exactly on 1030, but that has nothing to do with IBOC.
I'm not sure if KDKA is running IBOC anymore, I don't hear much interference on WBZ these days. Unfortunately for KDKA they take interference from WBZ and WINS so its become impossible to get a noise free signal from them here at night. You have to wonder how KDKA sounds near Philly as WINS and WBZ aren't that far away via skywave. Its sad to see such a historic station being jammed by the same owner, CBS.
I'm not sure if KDKA is running IBOC anymore, I don't hear much interference on WBZ these days. Unfortunately for KDKA they take interference from WBZ and WINS so its become impossible to get a noise free signal from them here at night. You have to wonder how KDKA sounds near Philly as WINS and WBZ aren't that far away via skywave. Its sad to see such a historic station being jammed by the same owner, CBS.
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rbrucecarter5
Guest
spunker88 said:
I don't know what is going on, but in my experience it takes tons of power, very low interference levels, a big antenna, and lots of luck to get AM HD decode.
When I was in Dallas, I was less than 10 miles from the KAAM 770 towers. Running 10kW, they should have been an easy decode. They never locked. KMKI 620 locked reliably, but full stereo was touchy at best. Both station's analog coverage was badly degraded from pre-IBOC days. When they were running C-Quam, I had reliable daytime stereo 290 miles on KAAM, 330 miles on KMKI. KAAM would have been, but co-channel KKOB was interfering, causing platform noise. Contrast that with their stereo range on HD - 10 miles instead of 300. A ten mile radius would be a tiny portion of the DFW metro area. Madness.
From Houston - about the only IBOC around is 1590 KMIC - no reliable HD less than 20 miles from the towers. 1620 from College Station - I hear the hash, no HD decode. WOAI 1200 at about 200 miles, with a large loop I get HD decode - mono only. Least little bit of lightning crackle or other interference - HD is gone until it comes back into lock again when the interference is gone. Which leads me to my greatest gripe of all. In a car, you could potentially go from normal volume HD to VERY loud volume power line noise very abruptly, causing the driver to be startled. That, my friends, is a safety issue.
WBZ is the #1 AM in Boston. WINS is the #1 AM in NYC, 7 ranks higher than WCBS. Even though WINS is being "clobbered" from both directions by KDKA and WBZ.
Remember that HD is 1% of analog power. 1kw analog has 10 watt HD, 5kw analog has 50 watts HD, 10kw has 100 watts HD and 50kw analog runs 500 watts HD.
Consider the source. Mr. Savage has a legitimate complaint about IBOC. Most of the other haters of IBOC just "don't like" IBOC period. No reason other than they just don't (or are unable to) understand digital radio. It is always the same (very vocal) handful of people who can't seem to ever get HD to "lock" properly. Unless you own a radio station that is adversely affected by IBOC like WYSL is; or you have proper equipment to accurately determine how and why IBOC "doesn't work" and can explain the reason(s) in an intelligent manner, your "credibility" is about as real as my phony "iyiyi" handle. At least I admit I ain't smart enough to pour piss out of a boot with the directions on the heel.
Keep grinning...
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Remember that HD is 1% of analog power. 1kw analog has 10 watt HD, 5kw analog has 50 watts HD, 10kw has 100 watts HD and 50kw analog runs 500 watts HD.
Consider the source. Mr. Savage has a legitimate complaint about IBOC. Most of the other haters of IBOC just "don't like" IBOC period. No reason other than they just don't (or are unable to) understand digital radio. It is always the same (very vocal) handful of people who can't seem to ever get HD to "lock" properly. Unless you own a radio station that is adversely affected by IBOC like WYSL is; or you have proper equipment to accurately determine how and why IBOC "doesn't work" and can explain the reason(s) in an intelligent manner, your "credibility" is about as real as my phony "iyiyi" handle. At least I admit I ain't smart enough to pour piss out of a boot with the directions on the heel.
Keep grinning...
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iyiyi said:
Last I checked the HD is off at KDKA so WINS or WBZ shouldn't have any interference. Even when it was on the interference on the analog signal was probably minimal inside the market. But you miss the point here, the HD signal is the one having problems working inside a station's service area, the analog one works fine. Its hard for a 500 watt HD signal to work within its market when a 50kw analog skywave station is on the same channel. For example KDKA's 50kw analog 1020 skywave in the greater Boston area interfering with WBZ's left side HD Radio carrier. At night there are signals on nearly every frequency interfering with HD so only needing a single sideband won't help.
But skywave isn't the only issue for IBOC, there is also lightning discharge and other electrical noise which will knock out HD reception even within a station's service area. This is a characteristic of the medium wave band, and not IBOC's fault, but it is an issue that iBiquity wants to pretend doesn't exist.
There are videos on youtube showing this:
http://www.youtube.com/watch?v=szd7lzGcyLU
http://www.youtube.com/watch?v=Ej31AftNYy8
The analog and HD signals are completely different animals. Both signals must make concessions to accommodate each other. Analog can't run CQUAM because the phase modulation of the L-R would heterodyne with the quadrature aspect of the HD information. This would cause false signals to appear in the HD demodulator. Analog must brick wall the frequency response to 5kHz because the higher audio frequencies will intrude into the linear portion of HD, again causing false info.
HD must compromise by leaving +/- 5 kHz of/and the center frequency clear for the AM signal to occupy. The HD "carriers" that bother so many people exist solely to cancel out interference and heterodyning that the HD QAM signal would cause to the host station. Pure HD signals have zero carrier emissions. The HD info heads straight for a PLL that locks as low as 0dB S/N ratio! (I don't quite know how they do that but it works!) If a pure HD station were to sign on, you would only hear a constant whooshing sound maybe 6 to 10 dB above the noise floor of the channel assigned to it. There would be no buzz or other interference on the adjacent channels.
HD must also concede additional buffering to accommodate the 8 second analog signal delay. Kill the analog and HD behaves like any other unlimited digital device and buffer the signal immensely. Remember the first portable CD players that would drop out everytime it was bumped? Now you can jog with a CD player and suffer no dropouts. Why? Some genius decided to give the device plenty of buffering to allow it to time to recover the signal lost while the lazer re-synchs. Electrical noise and static should have very little effect on a proper MW HD signal.
CQUAM has a 25Hz pilot tone. The decoder counts 7 cycles (about 1/3 of a second) and if the signal is good, it will go stereo. Any noise pulse will kick it back into mono for at least 7 cycles. Should the noise level be more severe, the decoder will count 37 cycles (about 1 1/2 seconds and retriggerable with every successive noise pulse) before going back to stereo. Big buzz kill if this happens while you're driving down the highway banging on the dashboard digging a favorite song!
Whole lot of other differences between analog and pure HD!
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HD must compromise by leaving +/- 5 kHz of/and the center frequency clear for the AM signal to occupy. The HD "carriers" that bother so many people exist solely to cancel out interference and heterodyning that the HD QAM signal would cause to the host station. Pure HD signals have zero carrier emissions. The HD info heads straight for a PLL that locks as low as 0dB S/N ratio! (I don't quite know how they do that but it works!) If a pure HD station were to sign on, you would only hear a constant whooshing sound maybe 6 to 10 dB above the noise floor of the channel assigned to it. There would be no buzz or other interference on the adjacent channels.
HD must also concede additional buffering to accommodate the 8 second analog signal delay. Kill the analog and HD behaves like any other unlimited digital device and buffer the signal immensely. Remember the first portable CD players that would drop out everytime it was bumped? Now you can jog with a CD player and suffer no dropouts. Why? Some genius decided to give the device plenty of buffering to allow it to time to recover the signal lost while the lazer re-synchs. Electrical noise and static should have very little effect on a proper MW HD signal.
CQUAM has a 25Hz pilot tone. The decoder counts 7 cycles (about 1/3 of a second) and if the signal is good, it will go stereo. Any noise pulse will kick it back into mono for at least 7 cycles. Should the noise level be more severe, the decoder will count 37 cycles (about 1 1/2 seconds and retriggerable with every successive noise pulse) before going back to stereo. Big buzz kill if this happens while you're driving down the highway banging on the dashboard digging a favorite song!
Whole lot of other differences between analog and pure HD!
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You have explained why the 25kw of WFLA is so HD crappy, here in beautiful Sa-ra-so-ta!. I can assume they are only running, at best, 250 watts from Racetrack. I am lucky if I receive ANY HD, here. They must be running a very efficient array.iyiyi said:
And with that 7 uninterruptable cycles, you can see why I called it psuedo-stereo. I thought they should have worked something out better. I would touch the horn and make the radio restart the count. C-quAM was destined to fail as a result, and it did.
Jeff in Sa-ra-so-ta!
Most AM programming is talk so I don't think there is much motivation to get stereo broadcasting.
Also I'm not sure how a CD player anti-skip buffer would work with HD Radio. A CD player could be considered 2 way communication because you can request x position on the CD. When the CD player is bumped and the lazer re-aligns it is able to pick up where it left off. So say you are listening at 0:30 and the lazer is reading at 1:00 using a 30 sec buffer. The lazer loses its position for 5 seconds, you are now listening at 0:35 and the lazer is able to go back and start reading from 1:00 at the same point it lost its position.
With a broadcast you can't go back, those 5 seconds are lost even if a buffer is built up that will just delay the HD drop.
Most digital communications that work well in noisy environments are 2 way. Wifi can work on noisy channels with other routers because the receiver can have corrupt packets resent on demand.
I'm still waiting for the day we see a non-hybrid IBOC station on both AM and FM that broadcasts at 100% power of the former analog channel and doesn't need sidebands if possible. It may be able to overcome interference at a greater power level and by staying on channel you wouldn't have to worry about other stations interfering. But nobody has done this yet.
Also I'm not sure how a CD player anti-skip buffer would work with HD Radio. A CD player could be considered 2 way communication because you can request x position on the CD. When the CD player is bumped and the lazer re-aligns it is able to pick up where it left off. So say you are listening at 0:30 and the lazer is reading at 1:00 using a 30 sec buffer. The lazer loses its position for 5 seconds, you are now listening at 0:35 and the lazer is able to go back and start reading from 1:00 at the same point it lost its position.
With a broadcast you can't go back, those 5 seconds are lost even if a buffer is built up that will just delay the HD drop.
Most digital communications that work well in noisy environments are 2 way. Wifi can work on noisy channels with other routers because the receiver can have corrupt packets resent on demand.
I'm still waiting for the day we see a non-hybrid IBOC station on both AM and FM that broadcasts at 100% power of the former analog channel and doesn't need sidebands if possible. It may be able to overcome interference at a greater power level and by staying on channel you wouldn't have to worry about other stations interfering. But nobody has done this yet.
1000 kHz to close to 1060 kHz has been one big hiss fest here in central Ma for four or five years now, maybe someone should send CBS a CD of the noise, oh yeah they obviously don't care, they're going to make big bucks off the noise soon from Kia owners. As far as I know KDKA has been off for about two years. All the NY IBOC stations spew hash up and down the dial here. It's probably WINS that is covering WBZ. IBOC hash sidebands will spew across half the country at night
I think the sidebands are delayed different amounts, so that if the signal is totally lost for 2 seconds, the other sideband should fill in the missing data and it theoretically shouldn't drop out. But I always lose HD lock when traveling under overpasses when FM Buddy shows the analog signal strength between 60-80 dBu at the location, even at 70 mph when the signal is disrupted only for a second at that speed. Listening to an HD2 on a class B seems to go from being perfect for 20 miles, about 10 miles of choppy reception, and then nothing while the analog is good for 20 more miles. Whereas I can hear an Internet stream without interruption on my phone even when the 3G signal is -110 dBm.spunker88 said:
With streaming, you are listening to your choice of stations by way of a third party. OTA is much simpler, it is the radio station and your radio. It is a much simpler, and thereby, more reliable system. The third party is the US Government that is controlling both. But, it is much more difficult for someone to disrupt OTA than it is streaming where everything has to work perfectly for you to receive anything. Streaming is using low powered cell sites designed to travel short distances. You need plenty of sites for dependable reception. OTA is designed to go many miles, and in some cases, hundreds of miles.Nick said:
I fear a time when everybody will become too comfortable with streaming. You can see that with just the battles between the carriers about how much to charge for data transfer.
There are bills through Congress suggesting a "switch" to turn off the internet due to "security concerns". Remember the echo from the past, "When you give up your freedom for security, you give up both." When was the last time you went through an airport?
I'll put up with the static, I have enjoyed a personal and professional relationship with my radio for all my life.
Jeff in Sa-ra-so-ta!
The big problem with cellular and internet is that they require a bandwidth for each user, even if they are streaming the same thing. Under normal conditions the infrastructure is built to have enough bandwidth, but in emergencies bandwidth can be hard to get. In the 2003 northeast blackout, even though cell towers had generator backups, many calls wouldn't go through because there wasn't enough bandwidth due to the higher than normal demand. Radio covers all of its users with the same amount of bandwidth so you don't have to worry about it going down in an emergency.
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rbrucecarter5
Guest
iyiyi said:
Lets address your issues, which seem to be with me. First of all - I am not a "hater". If that label applies to anybody, it would be the IBOC proponents in their vicious attacks on DX'ers. Throughout the history of broadcast radio, DX'ers have been treated with respect as the best (and earliest) indication to station engineers that something was wrong with their transmitter chain. Often times, a subtle loss of range pointed to an impending transmitter failure that cost much less to repair when detected early. DX'ers have also been a friend of station engineers when they alert them to interference issues when another station wrongly leaves their power on, makes an unregulated (or regulated) change that affects listening area.
Overnight, when DX'ers raised alarm about the sacred cow of IBOC - we were attacked viciously as being outdated, outmoded, old fashioned throwbacks - obsolete in today's world. What we were trying to say, as a group, is that in an era when AM is dying - in large part due to interference issues making the band unlistenable, especially at night - the AM band did not need yet another source of MAJOR interference. Between foreign language jabbering from south of the border, a glut of ridiculous new allocations all over the band, the proliferation and legislation of CFL bulbs, home networking, poorly designed microcontrollers in more and more electronics - the average home is fast becoming a very hostile environment for AM reception. Now - stations want to add very powerful digital hash to the noise floor of an already troubled band? MADNESS! Especially when it is becoming increasingly clear that HD zaps the range of the analog signal - thereby decreasing building penetration (if you don't care about the fringes). WOAI shuts off HD for a few days - reports come in from all over about the increased analog converage. You can't tell me that didn't mean better building penetration in San Antonio where the station cared. Look at the San Antonio board - I didn't start nor solicit the thread, it showed up on its own.
Yes - I've done careful scientific experiments of my own documenting the phenomenon. That doesn't make me a hater - I am a scientist. If HD worked, I'd have the integrity to report it. It does not. As a careful, seasoned DX'er who really understands engineering and the scientific method, I know what it takes to receive stations with in HD - I have multiple HD radios and the experience making antennas and finding and eliminating interference. If I can't make it work - the problem isn't with me and my equipment. It is with IBOC. What should be alarming to you is not that someone is speaking out about the deficiencies of the system. What should be alarming you is that if an experienced engineer is having trouble making it work, the average clueless consumer is going to take one try at it, and if it doesn't work perfectly the first time - they will return the radio as defective and never give HD radio another chance. Which is exactly what is happening!
As for your comment about sideband power, here is a careful, repeatable observation that I challenge you or any other HD advocate to perform. Travel to a rest area near Grenville New Mexico on highway 64/87. It is very remote, and you can only get a handful of radio stations at all, only one semi-local. Tune your car radio to 660, 680, 730, 770, 790, 880, and 900. You will clearly hear IBOC sidebands from Chicago stations - in the daytime. There is no trace of the analog signal or carrier. But I have tried this on several occasions, at different times of the day and year, and it is consistent. This is very alarming, because it means that the nature of the digital sidebands is that the modulation is extremely persistent, far beyond what you would normally expect. It is also very exciting to me as a DX'er, because it raises the possibility of incredible range should full digital ever be implemented. Sadly, I didn't have an HD radio to try for decode on the hybrid digital sidebands - but it would not surprise me a bit if you could decode HD with the right setup at that location. That said - I doubt 720 would decode because there is a weak signal on 710 at that location. Nighttime is even more alarming - because I can clearly null WOR sidebands in Texas, and have verified that the null I am throwing is in the precise angle of the WOR towers with a degree. There is no trace of WOR analog in Texas. Again - horrifically persistant digital hash. Fly out here, do it yourself. I've got nothing to hide, the result will be independent of the observer's position on HD radio.
What did work - and still would - is C-Quam. If the HD radio people had been smart, they would have recognized the problems early on - re-imaged C-Quam as "HD AM", and moved on. Instead, there was a very alarming, almost religious zeal about covering up the problems with the system - accusing and opposing opponents as almost heretics because we are attacking the unassailable. If the system were so great - then there wouldn't be technical problems, and there sure wouldn't be the need to persecute opponents. But this whole issue smacks of cover ups, high pressure bullying sales techniques, payoffs under the table, and all to cover up some really BAD engineering and protect the reputation of some people who totally blew it when it came to digital radio. When HD radio inevitably implodes, it is going to be the DX'ers who get the blame - not the engineers who didn't do their job properly. If they had, they would have made a system that worked in the first place, and everybody, including DX'ers but more importantly the consumer would have enthusiastically embraced the system. Instead, there needs to be scape goat and I guess DX'ers are a good place to start.
spunker88 said:
Reed-Solomon error correction, my friend! The digital data from several different packets is shuffled like a deck of cards. Therefore, signal dropouts affect relatively small amounts of data from each packet. The error correction algorithms reassemble the data in correct order at the receiver. It then estimates any lost data by comparing the info before and after the signal loss and wings it from there. Also the receiver switches to a lower bitrate in very noisy conditions. HD is currently hobbled because it must be synched with the "real time" (8 seconds delayed) analog signal, which cannot be "reshuffled" like digital data. Kill the analog and HD radio is free to utilize ALL of the benefits that digital can provide.
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rbrucecarter5 said:
Technology, as everything else, is trumped by Politics. Always has, always will.
Your history does not go back far enough for AM Stereo technology. ISB should of, and could have, been authorized as the AM Stereo standard back in 1960. It wasn't, and neither was TV - because of Politics.
C-quAM "standard" to which you refer was a Political Motivation from Motorola and their appointed accomplices in the right places in Washington. C-quAM was a poor attempt at AM Stereo by virtue of its counting pulses.
I would direct you to the Visteon "Jump" windshield mounted HD radio. It is, by far, the best of the HD radios and it is an easy install. You will be able to further your studies because your observations have merit.
I have seen a degradation in analogue signals but I chalked it up to added interference attenuating the signal at the receiver.
When it comes to DXers, ever since the FCC reduced the protected areas of clear channel stations to 750 miles back in 1980, the attacks have been ever so much stronger and shorter range. Even 970WFLA doesn't care about South of the Bay, anymore. Sa-ra-so-ta! used to be very important to them, not any more. Localization, is where it's at now. I figure it came from having so many overlapping markets due to consolidation. I am part of the Sa-ra-so-ta! cluster, now, and no more a part of the Tampa market. And the early days of cable TV penetration and more channels with only a certain amount of channels available on the cable, the adjacent market channels had to fight with carriage rules.
Most people don't even know there is still OTA channels, such as it is. I have an antenna aimed toward Ft. Myers for blacked-out Buc games. But when we stamped out analogue TV, I went from about 30-50 channels OTA to 0 on a portable TV. I still have the digital TV in my glove compartment, but it takes up space until I get "North of the Bay".
Jeff in Sa-ra-so-ta!
rbrucecarter5;
I have no issues with you or any other person here.
Check out "The Virtual Engineer" website and click on the AM radio forum. I have 3 posts on that site that I did late January 2010. I lasted only about 3 days there. Same iyiyi handle. Those posts (assuming they are still there) expounded some of my ideas about AM to some REAL radio engineers. Check those posts out and see if any of my (or their) ideas on AM broadcasting resonate with any of your thoughts on AM.
I suggest that you reconsider the source of the daytime buzz on those frequencies cited in your post. It may be possible that those signals emanate from Mexico or elsewhere.
PS. I agree with badjef's post #16 (above).
Later...
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I have no issues with you or any other person here.
Check out "The Virtual Engineer" website and click on the AM radio forum. I have 3 posts on that site that I did late January 2010. I lasted only about 3 days there. Same iyiyi handle. Those posts (assuming they are still there) expounded some of my ideas about AM to some REAL radio engineers. Check those posts out and see if any of my (or their) ideas on AM broadcasting resonate with any of your thoughts on AM.
I suggest that you reconsider the source of the daytime buzz on those frequencies cited in your post. It may be possible that those signals emanate from Mexico or elsewhere.
PS. I agree with badjef's post #16 (above).
Later...
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Whoa, whoa, whoa (or is it WHO, WHO?) 
Hey iyiyi - do I read your earlier post to say, WBZ has been experimenting with LSB IBOC, attentuating the upper digital sideband?
If this is the case - without your compromising your source - do you know this authoritatively to be true?? If it were we would be very interested to know. Thanks.
Hey iyiyi - do I read your earlier post to say, WBZ has been experimenting with LSB IBOC, attentuating the upper digital sideband?If this is the case - without your compromising your source - do you know this authoritatively to be true?? If it were we would be very interested to know. Thanks.
I have heard them after midnight with HD locked in. I heard WHO with no problems on a Sony Walkman right next to the HD receiver. 1020 was one loud buzz and 1010 WINS came in fine. Not scientific or authoritative and I have no idea how often they experiment with that method. That is when I jumped in big for IBOC because independent sideband is the only practical scheme for analog and/or digital MW broadcasting. WBZ usually runs IBOC on both sidebands (they are right now). The next time I hear it I will post it for you immediately! It is very possible that other posters have heard BZ or other IBOC stations testing single sideband but don't understand the mechanics. If anybody hears an IBOC station with the buzz on only one adjacent channel, that's what they are doing! I have also heard IBOC with various reduced levels of buzz on one adjacent and full buzz on the other. There are enough DXers here that may have heard this type of testing. Hopefully other DXers can add their input now that they know what they may have been hearing. We can consider this info as total B.S. unless or until others weigh in with similar reports. Hope that helps you!
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