Quadraphonic AM Radio - Maybe a first?

[Lucanu]

http://ourworld.compuserve.com/homepages/kevtronics/

this is an updated site where find info and stations worldwide (even a sample) from AM stereo.

BTW, the italian radio station is called "Radio Studio X"

www.radiostudiox.it

 

[The Quadfather]

Yes, I am sure that the station I mentioned is not broadcasting in stereo. There would be no point. Rush does play a lot of "bumper" music, but his listeners are not there for stereo bumpers. Digital radio would not benefit this station at this time because the installed base of receivers are strictly AM. To go digital suddenly would be to surrender the listener base. It's not needed anyway. The reception is fine for talk. Of course, my reception could use some improvement because the receiver picks up a lot of noise from the studio equipment at the TV station where I work.

But digital broadcasting is a chicken and egg problem. We just implimented digital television and high def, and we now are simulcasting. This gives a period of time for people to change over as their equipment wears out, or as their wants dictate. But in 2009 the old RCA analog transmitter goes dark and the digital will be the mainstay. This is mandated by the FCC, so it will happen. They may change the cutoff date but we hope not, for we can no longer find parts for the aging RCA TTU60D. By the way, guess what the new transmitter's model number is? Would you believe QXD-1? I guess it's fitting as what comes out of it is multichannel. In fact, I was very proud of the fact that we were the first station to broadcast in multichannel sound, and I don't know if the other stations have caught up yet. I admit that though I did put together our DTV system, I had no hand in the fact that we were multichannel first. That owes to the way the unique Fox supplied switching system works. For network, the Mpeg stream is switched from our flexicoder Mpeg encoder straight to their receivers, which put out an Mpeg stream, using a Terayon splicer. There is no decoding of the data stream, so the viewer gets everything the network sends, including surround. The other stations demodulate, switch, and remodulate. Because the station management are trying to do it on the cheap, they won't invest in a Dolby encoder until they absolutely have to. Surround gets dropped along the way through the studio control room. But when we do secondary channels, we will have to do it the same way they do, and I will do my best to make sure the Dolby AC-3 surround encoder is in the proposals where apropriate. (you wouldn't need surround on a weather radar channel).

But the more surround is popularized, the better chance we will get what we want. After all, it was home theater that kept surround in existence during the barren period between the fall of quad and the rise of DVD Audio. And it was DTS, a movie format, that first used a digital surround codec to release surround music for home use. So we owe a debt of thanks to DTS for the digital music libraries we have today. After the fall of quad, all the quad recording gear was eventually demolished, and the world went back to stereo. But now, thanks to the movie industry's adoption and popularizing surround, there will always be an installed base of surround recording facillities, and also the same for playback gear in the home. So the surround option will always be there. It will be up to the industry to use it. Hopefully at some point, there will be a sufficient demand to make it worthwhile. Another thing that might help is the emergence of a high definition video disc that has lossless surround audio. That will make DVD-Audio and SACD obsolete, I believe that has already been developed. Audio discs can be made using this format. (But of course, there will be a format war). Well, I reckon I have rambled on long enough, so I will let it go.

The Quadfather

 

[jaybird100]

Lucanu, I checked out that website and it was quite interesting, although I did find an error on their station list for Florida. One station listed, WWFE in Miami, has not been stereo for quite some time.

Quadfather, I wonder why you think the listener base would be lost if that station went digital. Like the TV station you work for (which one, BTW?)
stations broadcasting digital via HD Radio also simulcast. It's IBOC, so listeners with old AM analog radios are not lost. There are talk stations here in South Florida which have made the move, and they sound excellent. The only time you can tell they're digital when you listen to an analog radio is when they plug their digital capability. Otherwise, you would never know the difference. As for the date of the "Big Switch-off", it's pretty much set in stone for Feb. 17, 2009. Since I sell TV's, I have to make sure customers who are buying an analog set (yes, we still have a few) know about what's going to happen on that date.
You'd be amazed at how many people had no clue about it. The FCC also blew the opportunity to move all TV broadcasting to UHF, as many countries have already done. But we'll see; it could still happen. Tme will tell...

 

[Dylan Berichon]

Lucanu, I checked out that website and it was quite interesting, although I did find an error on their station list for Florida. One station listed, WWFE in Miami, has not been stereo for quite some time.

Quadfather, I wonder why you think the listener base would be lost if that station went digital. Like the TV station you work for (which one, BTW?)
stations broadcasting digital via HD Radio also simulcast. It's IBOC, so listeners with old AM analog radios are not lost. There are talk stations here in South Florida which have made the move, and they sound excellent. The only time you can tell they're digital when you listen to an analog radio is when they plug their digital capability. Otherwise, you would never know the difference. As for the date of the "Big Switch-off", it's pretty much set in stone for Feb. 17, 2009. Since I sell TV's, I have to make sure customers who are buying an analog set (yes, we still have a few) know about what's going to happen on that date.
You'd be amazed at how many people had no clue about it. The FCC also blew the opportunity to move all TV broadcasting to UHF, as many countries have already done. But we'll see; it could still happen. Tme will tell...

AM HD can cause a bunch of problems on any tuner that goes out past 5 KHz of audio response. There's a bunch of noise.

I can't listen to any of the local AM HD stations on my wide band AM Stereo radio that's in one of my cars. Too much buzzing.

In AM HD, I think it has a strange artificial sound. It sounds like internet radio (at least that's how it sounds in my other car with the HD Radio.)

And AM HD doesn't sound as good as a clean wide band AM stereo station.

You also can't run it at night (yet, this will change soon.)

It has its advantages, but there are a ton of problems that I'm not sure will ever be worked out.

Making AM digital is like trying to make digital vinyl records. Sure, it could be done, but it seems kinda foolish.

 

[Lucanu]

Check out this one site too

http://meduci.com

there is (I think) an updated list (seems here in Italy there are two AM stereo stations, which is great to me).

 

[The Quadfather]

I assumed that the stations were having to turn off their analog modulators to go digital. I have done some research and I stand corrected. IBOC allows a digital signal to piggyback on a subcarrier. In TV we don't do it that way. We just transmit our 8VSB signal on a separate carrier. The analog and the digital radio signal occupy the same channel allocation. Good idea. I noticed that there may be surround possibilities, though it wasn't clear if that is for AM and FM or just FM frequencies. Hey, I wonder if we will finally get to use the "Multiplex out" jacks on the back of our quad era radio gear to decode IBOC? I love the older gear and that would be nice. Maybe some ham operator will sell a kit for this. I did notice in my research that there are several methods and that IBOC is a general term and doesn't define a specified format. Yes, it's the old bugaboo, format war! Anyway, I hope it takes off.

With digital TV, it was important to stick with it. We started with flea power and then added HD and surround. Then we upped the power. That we did, and it is taking off now. I went to Best Buy the other day, and there were no analog sets. The TV manufacturers should have quit making analog sets three years ago. But the trade mags were casting doom and gloom for digital TV even before anybody was even transmitting. hell, it took years for the FCC to pick a standard modulation scheme. And then they said that 8VSB was no good. That it was brittle. I have seen it and it is good. By the way if you want the full unmolested high definition signal, you must get it off the air! The cable and satellite companies compress the signals, and they are not obligated to carry the extra channels if any exist. We will be transmitting extra channels on our digital carrier. They won't be high def, but they will be 480P, and if I have my say, it will be surround and widescreen.

I work for WGXA in Macon, Georgia as the Assistant Chief Engineer.

The Quadfather

P.S. The cable companies screwed the pooch and went with QAM for their modulation standard for digital transmission. So that means that where you didn't need a box before to get all the unscrambled cable goodies, you need the box for all digital signals, high def or not. I understand that some tuners are being made that will receive QAM as well as 8VSB. A good thing if this is so. I will have to do more research.

 

[The Quadfather]

I'll let the radio boys figure out all the HD Radio problems. I'm in TV, it's not my worry.

The Quadfather

 

[jaybird100]

Dylan, just how many AM tuners today have the bandwidth to let you hear the "noise" that AM HD generates? I can't hear it on either my car radio nor my home theater tuner. With the AM band being as crowded as it is, it's the radio manufacturers who forced this issue to keep selectivity up. I have not heard anything like you describe for the sound of AM HD. What I get on my Accurian radio has been quite good.

Quadfather I just happen to sell TV's, and you're right that there are very few analog sets left out there. That's a good thing, since we're inching up on the 2/17/09 deadline faster than we care to realize. We have many sets in the store connected to a rooftop antenna, and we use that to show digital off-the-air reception, and the multicasting done by many of the Miami area TV stations. We keep one set on channel 6.2, which is NBC Weather Plus. (After all, in South Florida, if you don't like the weather, wait a minute.) This brings up a question for you... is there any compatibility between the ATSC and DVB-T systems? We do get a lot of tourists who want to buy sets here and take them to South America. Most countries are following the European lead for
digital broadcasting, so this becomes an issue. What can you tell me about this?

 

[jaybird100]

QF, you said the digital HD box is needed because of the use of QAM (not CQUAM, which is AM Stereo). I thought that if cable companies were sending some of the HD channels out without encryption, that the QAM tuner built into many HDTV sets would be able to receive them even if the cable were connected directly to the TV, bypassing a box. The TV would find them while doing its channel scan. Comcast does this here in the sunny south.

 

[atrocity]

I have seen it and it is good. By the way if you want the full unmolested high definition signal, you must get it off the air!

Yes...but even then, I notice that it's not really great at handling a lot of motion or fades/dissolves. Don't get me wrong, I mostly like it, but once in a while it seems to do something really weird that calls attention to the compression.

 

[Dylan Berichon]

I'll post a few clips of AM stereo and AM HD for you guys to compare soon.

I just moved and am with out internet at the apartment for the time being, so it may be a little while.

September 14th is the date that AM HD has been authorized for night time operation! It will be interesting to see what happens.

 

[jaybird100]

I expect that, with the start of AM HD at night, there's going to be some rather severe interference on many stations. The word on the street is that the digital signal superimposed over the analog will make a sound "like a swarm of bees" that will be rather obtrusive. Some people are taking a wait and see attitude about this, but if it's as bad as predicted, the ramifications could be very serious.

 

[The Quadfather]

Yes...but even then, I notice that it's not really great at handling a lot of motion or fades/dissolves. Don't get me wrong, I mostly like it, but once in a while it seems to do something really weird that calls attention to the compression.

It all depends on how many bits are allocated to the particular channel you are watching as to how well it performs. Also, the demands on the bit pool made by the program material make a difference. The quality of the signal received can have an effect also. We monitor our signal constantly and we have none of the artifacts you mention. We broadcast 720P and no secondary channels at this time. So the only program gets the whole shebang. In the future we will divide it up into possibly two secondary standard def channels and our main high def program. The encoder will share bits between these channels. The main channel will get priority, at the exprense of the others, one of which will have local information. There will no doubt be improvements in the algorithm so that the encoder can be more efficient in the future. However, we will have to wait and see how well the secondary channels perform.

The Quadfather

 

[The Quadfather]

This brings up a question for you... is there any compatibility between the ATSC and DVB-T systems? We do get a lot of tourists who want to buy sets here and take them to South America.

DVB-T is a system that incorporates Orthogonal Frequency Division Multiplexing and is incompatible with 8 level Vestigal Side Band transmission system used in the ATSC standard. ATSC is also not compatible with QAM that the cable companies use, but sets built for the U.S. may have QAM decoders in them for cable. You will have to send your South American buyers further south to buy their sets, unless you can get a hold of sets that will display both standards, or are made for that particular market. Good Luck!

The Quadfather

P.S. Look Ahead, Look South! (Old Southern Railway slogan)

 

[atrocity]

It all depends on how many bits are allocated to the particular channel you are watching as to how well it performs. Also, the demands on the bit pool made by the program material make a difference. The quality of the signal received can have an effect also. We monitor our signal constantly and we have none of the artifacts you mention. We broadcast 720P and no secondary channels at this time.

No doubt the lack of secondary channels is extremely helpful. No one here is dedicating the entire bit pool to a single channel...and it shows. Infuriatingly, the worst offender is our PBS station, which looks great...until something moves, at which point it becomes completely unwatchable.

 

[The Quadfather]

Yeah, anything that increases the error rate beyond a point can cause pixellation. A signal that is watchable in the country may not be in the city if the multipath correction (ghost cancelling) is not up to snuff. The newer sets have better ghost cancelling circuitry than the earlier sets. We also have to do everything we can to ensure that the signal leaving the antenna is clean. That way, you will get it the best it can be. But we took this attitude with the analog signal before it. We still do. TV engineers must make sure that when they encode more than one channel, that bit sharing is being employed, with the high def signal receiving priority. Of course, we (TV engineers) are all on a learning curve and we have lots to learn. But we'll get it right. I have run experiments with a secondary channel displaying the converted NTSC signal. Since it is the same program as the high def signal, this is the least bit efficient way to run it. We were able to get good pictures on both signals. So I know it's possible to run two channels, one at 720P and the other at 480P, and get good results. And it may be possible to run a weather slate or radar, something with little motion in addition. But we will have to wait and see. But these stations that run 1080I are not going to be able to run a second channel. I suspect there just aren't enough bits.

The Quadfather

 

[atrocity]

Of course, we (TV engineers) are all on a learning curve and we have lots to learn.

I remember all the weirdness when TV audio went stereo. We had a couple channels with devices that sensed whether the current audio was stereo or mono and, if mono, would switch in a stereo simulator. Of course, since just about any TV show spends a lot of time on mono dialog, the simulators would turn on then turn off then turn on then turn off then turn on then turn off constantly. One station figured it out and gave up on the idea fairly quickly. The other kept doing it for months. I finally called to complain and was actually put through to an engineer who said he knew what I was talking about, agreed that it was awful...and that I was the first complaint they'd ever gotten. He said the device was a nuisance to remove from the chain, but now that they'd gotten a complaint maybe it would happen. It took months, but they finally ripped the stupid thing out.

Another station took a completely opposite approach and wouldn't even broadcast a stereo signal unless the program material was stereo. Apparently they had some kind of auto-tripping on their tapes--they had a stereo station promo that would turn up once in a while during a mono program. Suddenly the stereo indicator light would switch on and the room would fill with sound. As soon as the promo ended, the light went back off and everything went to mono. Seems like a lot of work, but it was pretty cool. Definitely attention-getting.

 

[The Quadfather]

Suddenly the stereo indicator light would switch on and the room would fill with sound. As soon as the promo ended, the light went back off and everything went to mono. Seems like a lot of work, but it was pretty cool. Definitely attention-getting.

Yeah, That would have been a lot of work for most stations since the subcarrier generator is usually located with the transmitter. For us, that's about ten miles away. So a radio transmission of some sort would be required to signal the generator to turn on and off. We used the similator for awhile, but I turned it off as soon as we could rid our plant of single channel material. The weird part was that you would have two channels on a tape machine and only the left channel would be recorded with audio. Without the synth unit, that's how it would come out of the viewer's television. We kept the carrier on all the time. Not for the purpose of "lighting the light", but because we had no way to turn it off remotely. We had a Mosely remote control system, but it didn't have GPI's. We finally fed one of our router outputs back to an input and the audio through a mixer so that we could redub mono tapes and give them two channels if not real stereo. It was preferrable to mono and definitely preferrable to the synth unit kicking in. Eventually we were able to turn the synth unit off, though to this day it is still in the audio chain. When we went stereo, I had to rewire the whole studio, and that was a big job. Fortunately, I had anticipated the job, and had started to run stereo lines with new equipment installs up to two years in advance. We esentially had to put in a separate audio distribution network while the old one was still in place. It will be even worse when we start doing local high def or start doing secondary channels, which either requires similar upgrades. They will probably be both done at once.

The Quadfather

 

[tejanoboy]

I work at a radio station that is in AM Stereo, and one of my side jobs is to update the music library in our automation system.

Well, one of the songs that "the boss" decided he wanted added was Pink Floyd's "Us and Them."

So being the Quad geek I am, I decided to add the SQ encoded version of this track to the computer instead of the Stereo version (if for no other reason then I like the extra saxophone that is excluded from the Stereo version).

(I recorded it off of my SQ LP copy of "Dark Side of the Moon" which is in pretty good shape.)

How does a SQ encoded track fare after being broadcasted over an AM Stereo radio station? That's the big question, one I will answer soon.

So, if you live in Portland, OR, connect the SQ decoder of your choice to your AM Stereo radio, and tune into the only locally opperated AM Stereo station left in the area! Heh heh heh...

Quad on AM Stereo opens a whole new can of worms! Yes, it CAN work well, BUT not the way a lot of stations process the pulp out of the audio to get a higher average modulation.

C-QUAM, the system we use today, has certain limitations regarding separation, and remember that ALL matrices boil down to
L+R=Front, L-R=Back. So, when a sound is in the rear speakers, at that point L-R exceeds L+R, something C-QUAM has very strict limits about.

Most of the processors used with C-QUAM have this problem taken into design considerations, and they will "clip" off any extreme separations...
good-bye rear sounds!

AM Quad would work GREAT, IF we had stuck with the Magnavox PMX system that the FCC originally chose. (Before the deep pockets of Motorola helped them to decide on C-QUAM!)

So, playing matrix quad over AM can sound good, but levels and processing must be watched with care.

Never tried decoding WOWO through a matrix back when they were using PMX, but I DO have a couple of recordings of them in stereo, might try it just to see how good the "oops" factor is...probably at least once in their 12-year run with PMX, they played SOMETHING matrix-encoded?

TB

 

[Dylan Berichon]

Quad on AM Stereo opens a whole new can of worms! Yes, it CAN work well, BUT not the way a lot of stations process the pulp out of the audio to get a higher average modulation.

C-QUAM, the system we use today, has certain limitations regarding separation, and remember that ALL matrices boil down to
L+R=Front, L-R=Back. So, when a sound is in the rear speakers, at that point L-R exceeds L+R, something C-QUAM has very strict limits about.

Most of the processors used with C-QUAM have this problem taken into design considerations, and they will "clip" off any extreme separations...
good-bye rear sounds!

AM Quad would work GREAT, IF we had stuck with the Magnavox PMX system that the FCC originally chose. (Before the deep pockets of Motorola helped them to decide on C-QUAM!)

So, playing matrix quad over AM can sound good, but levels and processing must be watched with care.

Never tried decoding WOWO through a matrix back when they were using PMX, but I DO have a couple of recordings of them in stereo, might try it just to see how good the "oops" factor is...probably at least once in their 12-year run with PMX, they played SOMETHING matrix-encoded?

TB

I've made some airchecks of SQ encoded songs off of a high quality AM Stereo tuner. I could email something to you if you'd like.