BBS: SWEDX Conference: SHORTWAVE Date: 7/26/1992 From: JOHN ROSS The following very long message is cross-posted from the TVRO Satellite Television Echo Area: From: DAVID BENNETT AUDIO SUBCARRIERS as explained by Gary Bourgois (flash@lopez.uucp) on Let's Talk Radio's Friday Night Live transcribed from audio tape by Robert Smathers (roberts@triton.unm.edu) -=-=-=-=- All right, subcarrier audio. This is the whole reason I bought a satellite system in the first place. I shouldn't really use the term "bought", because that would let you think that I went out and actually had some real green money to do this with. Let us say this is the first reason I "scrounged" a satellite system because I knew the BBC was up there, and I had been a shortwave listener since I was a young baby (chuckle) practically ... and ... so that is what I wanted. I used to get mad. In the middle of the afternoon I'd be listening to the BBC and all of a sudden they say, "This frequency is now closing..." and, no kidding, it was gone. And you couldn't hear it for about four or five hours. There was this big hole in the afternoon and another one in the morning during the times I wanted to listen the BBC wasn't there. You could occasionally pull it in on a frequency direct from London, but boy was it noisy. So the thought of being able to listen to the British Broadcasting Corporation, one of my favorite radio stations, in full quality FM sound was what got me into this whole hobby in the first place. And I got to tell you, that was about the second thing I tried was the BBC and was amazed that it actually was there and in such superb quality. So the first exposure I had to satellite audio was in the standard subcarriers. So let's define some terms here. Subcarrier audio, like you are listening to now, is in a range of 5 to 8 Megahertz and rides along the top of the video. Now that video can be either video in the clear or it can scrambled video. An example of a channel that is in the clear that has a lot of audio on it is Galaxy 3, channel 11. That is Mind Extension University and I believe they have the most subcarriers of any satellite channel out there. Mind Extension University has got a slew of them because that's where all the Superradio, Galactic Radio, whatever they are calling it these days. The Jones Intercable channels which provide the new age of Jazz, and classical music service as well as country western music, rock and roll, and you name it. Every type of service is there in full stereo on Galaxy 3/11. And they use the whole bandwidth from 5 to 8 Mhz, there is something just about every 10 or 20 KHz you'll find another audio subcarrier. They are in pairs. It's interesting to note, and don't ask me why, but it seems that there was a standard settled up on a long time ago back in the early days of satellite that when you are transmitting in stereo, particularly discrete stereo which is what just about all of it is today, in subcarriers the left is always lower. For example, let me get the book out here -- I happen to have the official WestSat Communications Guide -- strongly recommended -- in fact I'll give you the address later where you can order one, and if you listen to Let's Talk Radio at all, you will hear people making reference to this really nifty book. It comes out about every two to three months and it is a list of all the different satellites and what you will hear on them. Some of the subcarrier services on Galaxy 3 -- let's go over to channel 11 -- you'll find that Superradio, America's ... that's what they are calling it now ... SuperAudio, uh, they've changed their name again (laughs), every time you turn around this service has a new name. America's Country Favorites, for example, the left channel is on 5.04 and you have to tune up to 7.74 for the right channel. So if you didn't have this list, you'd have to go hunting but you probably would find it eventually. Soft rock hits are on 5.22 left and 5.4 right, and that's discrete stereo. Now what we have here are FM subcarriers. In other words, the audio portion is an FM carrier and it is basically multiplexed onto the video carrier. What happens then is you have two, one for the left and one for the right. Now right now, you are listening to us on 6.2 wideband, and that is something to take into consideration. There is both wide and narrow band. The wide band subcarriers are around 100 KHz wide, and, actually closer to 200 I guess, around 180 or so, and the narrow band are somewhere between 60 and 70 KHz wide in FM deviation. And if you are a ham radio operator and have played it all with 2 meter FM, you know about deviation. It's basically the louder the signal is, the wider the carrier becomes. So you have wide band and narrow band. Most satellite receivers today have a wide and narrow position, and some do not. Some satellite receivers only have mono on the subcarrier and they get the stereo just only on the scrambled channels out of the So let's define some terms here. Subcarrier audio, like you are listening to now, is in a range of 5 to 8 Megahertz and rides along the top of the video. Now that video can be either video in the clear or it can scrambled video. An example of a channel that is in the clear that has a lot of audio on it is Galaxy 3, channel 11. That is Mind Extension University and I believe they have the most subcarriers of any satellite channel out there. Mind Extension University has got a slew of them because that's where all the Superradio, Galactic Radio, whatever they are calling it these days. The Jones Intercable channels which provide the new age of Jazz, and classical music service as well as country western music, rock and roll, and you name it. Every type of service is there in full stereo on Galaxy 3/11. And they use the whole bandwidth from 5 to 8 Mhz, there is something just about every 10 or 20 KHz you'll find another audio subcarrier. They are in pairs. It's interesting to note, and don't ask me why, but it seems that there was a standard settled up on a long time ago back in the early days of satellite that when you are transmitting in stereo, particularly discrete stereo which is what just about all of it is today, in subcarriers the left is always lower. For example, let me get the book out here -- I happen to have the official WestSat Communications Guide -- strongly recommended -- in fact I'll give you the address later where you can order one, and if you listen to Let's Talk Radio at all, you will hear people making reference to this really nifty book. It comes out about every two to three months and it is a list of all the different satellites and what you will hear on them. Some of the subcarrier services on Galaxy 3 -- let's go over to channel 11 -- you'll find that Superradio, America's ... that's what they are calling it now ... SuperAudio, uh, they've changed their name again (laughs), every time you turn around this service has a new name. America's Country Favorites, for example, the left channel is on 5.04 and you have to tune up to 7.74 for the right channel. So if you didn't have this list, you'd have to go hunting but you probably would find it eventually. Soft rock hits are on 5.22 left and 5.4 right, and that's discrete stereo. Now what we have here are FM subcarriers. In other words, the audio portion is an FM carrier and it is basically multiplexed onto the video carrier. What happens then is you have two, one for the left and one for the right. Now right now, you are listening to us on 6.2 wideband, and that is something to take into consideration. There is both wide and narrow band. The wide band subcarriers are around 100 KHz wide, and, actually closer to 200 I guess, around 180 or so, and the narrow band are somewhere between 60 and 70 KHz wide in FM deviation. And if you are a ham radio operator and have played it all with 2 meter FM, you know about deviation. It's basically the louder the signal is, the wider the carrier becomes. So you have wide band and narrow band. Most satellite receivers today have a wide and narrow position, and some do not. Some satellite receivers only have mono on the subcarrier and they get the stereo just only on the scrambled channels out of the videocipher. So, when you are buying a satellite receiver and you are interested in audio, one thing you should make note of: Does this receiver allow me to tune both wide and narrow subcarriers? And if it doesn't, does it at least have a jack on the back called "baseband video" so that you can add on a little gizmo we are going to talk about later called a stereo processor which will allow even the most primitive of satellite receivers to take advantage of some of stereo audio that is out there and there is a ton of it. There are two other types of stereo no longer in use that also use subcarriers. One was called matrix and the other is called multiplex. Now why would you have such a thing? Why would you have discrete stereo which is a separate channel for the left and a separate channel for the right, and then a totally different system called matrix which was an interesting thing that appeared ever so shortly and it just kind of vanished because it was too difficult to set up. The way that matrix worked, and that was interesting, this allowed you to transmit in mono so that people with a single audio knob could hear both the left and right channels, and the people who had a stereo processor could hear the left and the right using only two subcarriers. And the way they did that was the same way that FM stereo gets stereo signal out of two separate signals. And that is they use left minus right, which is a "difference" signal. And then you have this cute little circuit that does a bit of algebraic addition so you end up with the information from the left minus the right to let you figure out what the left is and figure out what the right is. So they were able to produce both mono on one subcarrier so that the people with mono receivers would hear both channels, and then by taking the left minus right and subtracting left minus right from the right channel and then also adding left minus right to the right channel you end up with two left and two right which is basically left and right. It is a complicated way of doing things and not very efficient. So this type of stereo is not used at all any more, but a lot of receivers still have a button that says matrix and if you push it, some interesting strange things happen because what it does is algebraically subtracts the one channel, the higher channel, from the lower channel and then it takes and also adds that so that in your left channel you have the right channel twice and in the higher channel, which would be the right channel, you have the "difference" signal. If you have it in headphones, you get some pretty weird effects, because everything that is in the center channel then disappears and you are left with a confusing mess. Anyway, that is not used anymore. The other type of stereo that is no longer used that you still find on a lot of the older satellite receivers is the button called multiplex or MPX. Now what this was is exactly the same thing as your standard stereo FM. They have a subcarrier and I don't know what frequency, I would assume 19 KHz just like regular FM uses, and they did the left minus right thing on this subcarrier of a subcarrier. How's that for confusing? Well, that is no longer used anymore either, so the only thing you have to worry about is discrete stereo when you talk about subcarrier stereo. What you have then is a separate tuning knob for the left and the right channel. On a more modern satellite receiver, you have a button called sub-audio, it may have a different name, but basically it does the same thing and you'll actually get a display on your screen that shows you the frequency to which you are tuned. If you are tuning mono, you only get one frequency to look at, but if you are tuning discrete stereo, you'll actually be able to adjust by pushing your up and down buttons to the exact frequency. What you'll need then is a guide to point you in the right direction of where to tune for these audio frequencies, or, in what is even more fun, is to go chasing them for yourself. Although with a more modern satellite receiver, that can actually be a chore because they go so slow, which brings us to this nifty gizmo, that you probably, if you are going to Dayton and you see any of these, grab them because (chuckle) for nothing else you will be able to sell them to somebody else who wants them because people are always looking for stereo processors. What the stereo processor does -- it connects to the baseband video in the back of your satellite receiver. Now don't think of this in terms of the regular video. Don't think of it as the RF that goes to your TV set. This is called either baseband or raw video, Sometimes it is called unclamped video. What that is, it is basically the entire bandwidth that the satellite receiver is seeing totally unprocessed, and that is really what you need, so that it has 0-8 megahertz coming out of the back of that satellite receiver. You then take that and connect it to the input of your stereo processor, which is nothing more than two completely separate receivers, and they tune -- they are FM receivers -- with both wide and narrow band and they tune generally in the range of 5-8 MHz. Now if you get in there with a golden screwdriver, you can sometimes change that -- so you can tune a little bit lower and hear some of the other things that we will be talking about in a little bit. This gizmo comes in two types. The older stereo processors, which were sold as an add-on -- because back in the original days of satellite TV what we had was a whole room full of boxes. There was no such thing as an IRD when this industry got started. You had a receiver -- that was separate -- you had a positioner -- that was separate -- and if you wanted stereo, you had another box just about as big as your receiver that just tuned your audio for you. The older ones, in fact the ones I recommend for someone who wants to go hunting for subcarriers like I do, has a little tuning knob which is basically a potentiometer that tunes a variable controlled oscillator and allows you to sweep that whole 5-8 MHz bandwidth in a second, and in that time you can hear if there are any carriers in there -- they'll stand out like a sore thumb and you'll know they're there. That is an excellent DX'ers tool if you are the satellite hobbyist and want to go hunting for stuff and checking out the satellites for subcarriers. Even if you have a nice modern satellite receiver, one of these add-ons - - the older stereo processors -- is a nice thing to have because it allows you to go through a satellite very quickly -- step through each transponder and zip-zip back and forth and see if there is any audio there. The one that I have here is called the Drake SA-24. It was made by Drake and it was made for use with one of their older 70 MHz systems and it does a real nice job. And also I picked up a Janiel -- I understand these are available again, for a while they weren't, in fact they are dirt cheap, the Shop At Home people are selling them for $39 and I can't imagine they will last too long, they must have apparently uncovered a truckload of them, they must have got them for practically free - - it is a Janiel Stereo Processor SP-2000. It basically has all the same functions as the analog processor does, and it is indeed dual analog receivers, but the interesting thing about the Janiel is it has a digital frequency readout. So you can actually know -- if I turn mine on here -- the last place I was on Radio Canada and I was listening to the left channel on 5.76 and the right channel on 5.94. That is a very popular pair on the Canadian satellites. The Janiel is nice for that. If you are considering the Janiel processor one thing that I do have to mention -- the only thing that is wrong with it, and everybody who has one will tell you the same thing, and if somebody could get ahold of a schematic for this, boy we'd all be in there with screwdrivers and wire cutters in a hurry to modify the one circuit that drives you crazy and that is the automatic bandwidth selection. Unlike the Drake unit stereo processor, which has a wide/narrow button, the Janiel does that for you automatically. What it does is senses the bandwidth, and if it is beyond about 75 KHz, it pops it into wide mode. To get it back into narrow, all you have to do is touch a button on the front panel of the tuner and it automatically goes back into narrow mode. The problem here is that the one thing that everyone wants to listen to is BBC, which is located on the CSPAN, which is one of the audio channels on Galaxy 3/24, and the BBC is found at 5.4 MHz. For some reason, that channel -- that one particular channel -- is just on the edge, so anytime there is a loud piece of music or even a loud voice, what happens is the receiver goes to wide band and you lose the signal. That is something to bear in mind if you are considering buying one of these Janiels -- that is the only thing wrong with it, and wouldn't it be nice if we could make that a manual function like it is on the older units. This is not a problem to listen to most of the channels that you will pick up, such as CBC Stereo or any of the Galactic audio narrowband signals -- no problem at all -- but with the BBC that is a consideration. I always want to let people know that because it is a universal thing, because I've had two of them and I know other people who have them and that is the same thing they say -- BBC you can't get -- so bear that one in mind. That is why it's nice to have two, because the Janiel has a little bit better sound than any of the other units that I have messed with -- and I don't know why -- it just has a different, brighter equalization and it seems to be a little less noisy. They have a thing on there called an expander -- and I am not exactly sure what that does -- it is not the DBX expansion, it is some other form of expansion that they use, and that helps. Some of the units also have digital noise reduction, or Dynamic noise reduction -- that's what the Drake has -- and if you ever see a stereo processor at a hamfest or you see one for sale expect to pay somewhere between $30 and $50. Much more than $50, no, don't. $50 is the maximum that you would want to get. Sometimes people will be asking $100 for these things -- I guess they were around $150, $200, $300 new -- the Janiel was $299 new, and now it is selling for $39 and the reason is that most people don't have all of this old satellite junk laying around anymore, in fact, most of you listening to us right now are probably listening to us on nice, modern, shiny, new IRD's and you simply have to hit "favorite audio 1" and there is Let's Talk Radio. For the experimenter, there is a lot of this older equipment laying around that is especially suitable for listening to audio. In fact, I know a lot of people who tell me the reason they can't listen to this program is because their wife has some show they have to see on Friday night and that's that -- she hangs on to the remote control. What I suggest to everybody is to go to a hamfest, go through your newspaper ads, check to see if there is any auctions in your area and pick up a second satellite system just to dedicate to audio and then go out and get all this neat stuff to add to it. Anyway, basically that is what subcarrier audio is. Subcarrier audio is just an FM signal -- just like your FM radio that you listen to every day -- the only difference is that this is part of the video signal and standard subcarrier audio is found multiplexed along with the video, and in the frequency range you will tune your receiver is between 5 and 8 MHz -- actually about 8.5 is where the bandwidth stops. Most television services transmit on 6.2, 6.8 and 5.8. The popular stereo pair for channels like CBS, who feed the stereo signals at 5.8 left and 6.2 right. As you are tuning through the slates on Telstar 301, you will see that all the stereo programs are transmitted in discrete stereo using that particular pair. FOX, on the other hand, has a strange pair that they use on their FOXNET, which is different from the FOX that you find on Telstar 303. There is also FOXNET, and FOXNET uses -- I should probably look it up to tell you exactly -- it is in the 7 MHz range and it is a very unusual pair that they use, but you'll be able to find it if you tune around. This will give you a lot more pleasure listening to some of these programs in surround sound, or even just regular stereo through your headphones or through the speakers. It adds a whole new depth to watching television. And what is really fun is when you can pick up the clean feeds like Northern Exposure or some of the other shows -- on Anik E2/12, the Global Channel, for instance on Thursday afternoons they've got LA Law, Cheers, the Simpsons, and a few other shows and that is also in stereo using the 5.8 and 6.2 stereo pair -- the quality is amazing. There is a lot to be said for digital stereo, and IRD's are nice, and having the stereo coming out of the back of the box is nice, but the real neat thing is to be able to tune these shows that don't have commercials -- it's actually like going to the movies, get yourself some popcorn, sit back, and enjoy discrete stereo -- it's stereo you'll never find on regular over-the-air television or cable TV. The only thing that is superior to that is digital stereo that comes out of your IRD and there are some people like myself who prefer the discrete stereo because digital is kind of raspy sounding, depending upon what types of sampling rate they use. Alright, now, from standard subcarrier the next thing we move in to is this thing called FM Squared, which people -- surprisingly just about every week somebody says "What is FM Squared and why do they call it that, and what's there, and is it worth playing with, and what do you need?" and you don't need much to explore FM Squared if you have a receiver that has both unclamped video - - raw video as we call it -- you can hook up a shortwave radio and get a bare taste of what is there. The problem you'll have with the shortwave radio is that you'll find the audio is distorted. The reasoning for that is because the bandwidth again is the same bandwidth basically as we use for the narrow standard subcarriers -- somewhere in the vicinity of 50 KHz wide. The problem is that shortwave radios don't tune 50 KHz in the high frequency range -- they tune very narrow bandwidths -- around 5 KHz, maybe 10 if you are lucky, so there will be only a few signals that you will hear -- most of it will be terribly, terribly distorted. But if you want to try that anyway, the trick is to hook to the raw video output -- the unclamped video in the back of the satellite receiver -- hook that up to the input of your shortwave radio and you can actually tune to the frequencies. Now what is FM Squared anyway? How do they do that? You'd think that in order for a subcarrier to work, it has to be multiplexed onto video. Well no, it just needs to be multiplexed onto a main carrier that is used to lock the receiver so it is fooled to think there is a video carrier there and the receiver's AGC, AFC has something to lock onto. And that is basically what FM Squared is is one main carrier and then -- that's an FM carrier - - and all of these other signals are also multiplexed on top of that carrier -- which means that is FM on top of FM or FM Squared -- that is how it got the name. Because there is no video on FM Squared, what they do is put all of the audio where the video normally would be and that is between 0 and 5 MHz -- that is where the video normally lives, and instead they put audio there and they do. * Origin: Top Hat BBS [+1 206-244-9661] (1:343/40)