Fullscreen HTML5Med Res (??MB)HTML4

Believe it or not . . . A $49 Satellite TV System Have you ever looked at those satellite dishes which have sprung up on pubs, clubs and even private homes and thought “Gee, I wonder what they’re watching?” Have you ever wished that you too could get into satellite TV reception – but have been scared off by the $$$$$? Wish no longer! By Ross Tester and Garry Cratt* 10  Silicon Chip H ere is a full satellite TV system which you can set up in your own backyard for a tad under fifty dollars. No, not five thousand and fifty dollars, not even five hundred and fifty dollars. Just fifty measly dollars. For that, you get a satellite dish, the mounting hardware, a LNB (low noise block converter) and an analog satellite receiver which you can plug directly into most TV sets (or video recorders). And yes, the price even includes the Generally Silly Tax. Point the dish in the right direction (we’ll tell you how later), tune the receiver (we’ll tell you how later) and start watching satellite feeds. If you’re into amateur television (or would like to be), this would be a great system to get you going. How is this possible? One of the consequences of rapidly changing technology is the huge amount of equipment made obsolete in just a few years. Thousands of still-operating ’386 and ’486 computers have no doubt gone to the junkyard or dump, replaced by the latest higher speed processor models. Most of us regard this as a terrible waste of manpower and money. But that’s “progress” (or is it marketing?) for you. Satellite TV has enjoyed as similarly short a lifespan as the personal computer and the amount of obsolete equipment destined as landfill is rap- Here’s what you get in the hardware department: the 90cm dish, the mounting plate, three mounting struts, the main mounting bracket (right) plus the LNB and its mounting bracket (bottom). Below is the Scientific Atlanta 9600 series receiver plus the 125VA enclosed 240/110 transformer. Not bad for $49.95, eh? idly increasing. It was a case of being “in the right place at the right time”. Garry Cratt, from the satellite reception specialists Av-Comm Pty Ltd, found a huge quantity of surplus satellite TV equipment sitting in one of his supplier’s warehouses, just a day or so away from being picked up by a metal recycler. The systems were obviously used (in some cases very used) but had all been nevertheless working perfectly when replaced a few months previously. Instead of the local dump or metal recycler’s, the whole lot – pallets and pallets of it – found their way to Av-Comm’s warehouse instead. And the price was what the metal recycler had offered! JULY 2000  11 These two shots show how the mounting bracket bolts to the mounting plate which in turn bolts onto the rear of the dish. The whole assembly is designed to slip over a 2-inch water pipe. Rotating the dish on the pipe allows you to set the azimuth, or direction, while adjusting the threaded rod on the right of the bracket (with the black cover on the end) lets you set the elevation, or distance above the horizon. Being an “offset” dish, it is more vertical than a “prime focus” dish. When the truckloads of equipment arrived, Garry took a closer look at his bargain purchase. The dishes were all in quite good nick, even if somewhat “shop soiled” (Garry used a slightly different expression but decorum prevents us quoting him verbatim). They were 90cm offset dishes, the type recommended by most K-band broadcasters because of their good sidelobe performance and no aperture blockage. Because an offset dish is actually only a section of a larger “prime focus” antenna, the offset angle means that the actual angle of the reflector FOCAL POINT FOCAL POINT OFFSET DISH PRIME FOCUS DISH Fig.1: the difference between a “prime focus” dish and an “offset” dish. In reality, an offset dish is a portion of a prime focus dish, having the same focal point as if it were the prime focus dish. This can best be illustrated by the diagram at right where the offset dish above is superimposed over the prime focus dish. As an offset dish is it mounts more vertically in higher latitudes, there is less pooling of water or build-up of snow and ice. They also have good side-lobe performance and, because the feedhorn doesn’t “get in the way” of incoming signals, no “aperture blockage”. 12  Silicon Chip FOCAL POINT with respect to the horizontal plane is much higher than that of a prime focus dish, ensuring that rain, ice and snow cannot pool on the dish surface. In simple words, the dishes are much more vertical. The “offset” part also means that the LNB is not mounted at the apparent focus of the parabola of the dish but is offset. Despite the age of the dishes and LNBs (probably a decade or so old), he was surprised to find they were capable of providing a result at least comparable with a brand new dish and LNBF combination, when used on the new Optus B3 satellite Aurora digital system (used to deliver ABC and SBS across Australia). Of course the system performance margin is less due to the higher noise figure of the LNB, typically 1.1dB. The satellite receivers are of similar vintage to the dishes and LNBs and, as such, are also a little soiled. But a few minutes with a rag and some metho does absolute wonders – we’re sure you could do the same too. The receivers, by the way, are Scientific Atlanta Model 9600 series, a brand very highly respected in the satellite TV world as offering superb quality. Designed to fit in a 19-inch rack, they’re also quite happy in a stand-alone mode. There are a couple of different models within the series but we’re not The feedhorn and its attached LNB first mounts in its own bracket (shown below) which allows it to rotate, thus setting polarisation. As shown (label up), the polarity is vertical. The feedhorn bracket is bolted to the three mounting struts which in turn bolt onto the dish. This shot also shows the RG-6/U cable connected and secured to the bottom strut with cable ties. Note the “drip loop” in the cable. high-performing receiver especially considering its age – and even more so considering the price. What’s it perform like? going to expand on the differences. What you get for your $49.95 is what you get! With 20-channel memory and a wide rage of user functions accessible from the front panel, they’re quite simple to use (unfortunately, there are no instruction manuals but the labelling is pretty much self-explanatory). On the rear panel are inputs from the LNB, vertical and horizontal inputs, IF out/IF in sockets (usually connected), video output and composite baseband outputs plus a range of connectors for audio output (stereo if available), remote control, presets for audio level, switches to invert and/or clamp video and so on. We won’t bother with many of these but they are there for you if you want to experiment. Most of the receivers operate on 110V AC but even here you’re not on your own. Included in the price is a 240/110V 125VA Ferguson transformer, housed in its own steel case, complete with 3-pin socket and mains lead. The replacement cost of this transformer on its own is about $90… but it’s included in the $49 deal. All in all it’s a very comprehensive, We’re not pretending that it has the performance of a modern system utilising a digital receiver and smartcard arrangement – but such a system costs just a little more than this system – well over $1500 in fact. This system is much cheaper yet is capable of providing more-than-watchable results. For under $50, it’s great value even for experimenters. Garry tells us that many have already been sold to amateur operators for ATV experiments – without any publicity at all. Word of a bargain soon gets around! This is an analog system – which is one of the reasons for its withdrawal from use. It is not capable of tuning digital signals but there are still plenty of analog signals to play with – for example, all of the network “interchange” signals currently being transmitted on the Optus B1 satellite. Using a small dish (90cm is considered small!) doesn’t give you the picture quality of a larger dish (say 1.8 or 2.5m) but the pictures are still perfectly watchable. The bigger the dish (within reason), the better the results. Also, modern LNBs have a lower noise figure than the LNB used in this system – replacing the LNB with a unit of more recent vintage would also improve the reception. Again, though – don’t look at the quality. Look at the price! By the way, the format of the re- ceived signal doesn’t change in the receiver: if you pick up a PAL signal from the bird, you get a PAL signal out. If it’s NTSC, you get NTSC out. Contrary to popular belief, you can watch an NTSC picture on a PAL TV – it’s just that glorious living Technicolor becomes glorious boring black and white. If you have a multi-standard TV set... lucky you! And before we get onto building and erecting the dish, a word on legalities. It will pay you to get in touch with your local council or building authority to check on their rules. Our local council, for example, allows a single dish up to 1.5m in diameter, ground or building mounted, to be erected without a permit. Anything larger, or more than one in your backyard, or mounted up high, requires a development application. Building the system First of all, check that you have all the bits. You should receive the 90cm dish, a mounting plate, three LNB mounting arms, the LNB itself, an LNB mounting bracket and the dish assembly mounting bracket which probably (but not definitely) has U-bolts still attached. Of course, you also get one of the Scientific Atlanta 9600 series receivers (ours was a 9630) and the Ferguson TS115/125B transformer, if required (for 110V receivers). You will also get many of the nuts and bolts needed to put it together – perhaps not all of them but for $49.95, what’s a couple of bolts between friends? What you don’t get is any coax JULY 2000  13 cable, mainly because every location needs a different length of cable, nor the “F” connectors which are essential to connect the LNB to the receiver. The first step is to give the whole lot a clean. Dust off the cobwebs (no, we’re not kidding!) and give the whole thing a bit of TLC. You might like to give any exposed or corroded parts a spray with some WD40. Even though the dish “reflector” is one piece, there are a quiet a few other bits of hardware involved, hence the most logical assembly sequence is outlined here. Bolt the mounting plate to the mounting bracket – when the recess in the mounting plate points up, the mounting bracket sits on top of this. The holes in the mounting plate are threaded so no nuts are needed Bolt this assembly to the back of the dish. There are four bolt holes in the dish which correspond to the four bolt holes in the plate. To ensure there are no protrusions onto the reflector surface (reducing the dish efficiency), the bolts are countersunk. Simply bolt the backing plate assembly to the back of the reflector with the bolts going from front to back (ie, through the dish then through the mounting plate), ensuring the mounting pole entry point faces towards the bottom of the dish. A feedstrut mounting hole helps to identify the bottom of the dish. Make sure these are well and truly tight – these bolts stop the dish vibrating in the wind which in turn helps ensure picture stability. Put the dish assembly aside for a moment while you get the LNB assembly ready. Its bracket grips to the throat of the horn with two nuts and bolts (see photo opposite). Just finger-tighten the nuts for the moment. There are three struts which hold the LNB assembly in place – two the same length and one shorter. The two longer ones are horizontal struts while the shorter one is the bottom strut. Each strut has a square end and a rounded end. The left-hand and And here’s what it should look like when it’s all finished and ready to go. Compare this photo with the side-on shot on page ??? and you should have no problems working out what goes where. (The knee bone’s connected to the thigh bone, the thigh bone's connected...) The tropical-looking setting, by the way, is in the suburbs of Sydney! 14  Silicon Chip Table 1: ANALOG CHANNEL LIST K BAND (viewable with this [90cm] dish) FREQ USER POLARITY VIDEO AUDIO OPTUS B1 (160 degrees east) 12386 Network 7 Horizontal EPAL 7.38/7.56 12451 Herbalife Horizontal PAL 6.60 12458 Network 10 Vertical PAL 7.38/7.56 12480 Network 10 Vertical EPAL 7.38/7.56 12488 Network 9 Horizontal EPAL 7.38/7.56 12728 Network 9 Vertical PAL 6.60 12739 Herbalife Vertical PAL 6.60 C BAND FREE TO AIR IF FREQ 1086 MHz 1151 MHz 1158 MHz 1180 MHz 1188 MHz 1428 MHz 1439 MHz (viewable with a larger [>2.2m] dish) APSTAR 2R 76.5E 3750 VATSA (India) Vertical PAL 6.2/6.8 1400 MHz THAICOM 3 78.5E 3507 Raj TV 3535 ATN 3649 Thaicom test 3649 VTV Vietnam 3685 MRTV Vertical Vertical Horizontal Horizontal Horizontal PAL 6.60 PAL 6.60 PAL 6.60 PAL 6.60 NTSC 6.60 1643 MHz 1615 MHz 1500 MHz 1500 MHz 1465 MHz INSAT 2E 82E 3557 Vijay TV 3579 Jaya TV 3655 Asianet 3809 DD5 Tamil TV 3850 DD1 Metro 3930 DD2 National 4089 DD7 W Bengal Vertical Vertical Vertical Vertical Vertical Vertical Vertical PAL PAL PAL PAL PAL PAL PAL 1593 MHz 1548 MHz 1495 MHz 1341 MHz 1300 MHz 1220 MHz 1061 MHz ASIASAT 2 100.5E 3885 Worldnet USA 3960 CCTV 4 China 3980 RTPi Portugal Horizontal Horizontal Vertical PAL 6.60 PAL 6.60 PAL 6.6/7.2 1265 MHz 1190 MHz 1170 MHz GORIZONT 25 103E *** (Inclined orbit) 3675 RTR RHCP SECAM7.02 1475 MHz ASIASAT 3 105.5E 3650 Marathi 3760 Now TV 3800 Star Sports 3840 Channel V 3900 Punjabi TV 3920 Phoenix 3940 Zee News 3960 Star World 3980 Zee TV 4100 PTV 4120 CCTV4 4140 Bangla TV Vertical Horizontal Horizontal Horizontal Vertical Horizontal Vertical Horizontal Vertical Vertical Horizontal Vertical PAL 6.60 PAL 6.60 NTSC 5.9/6.2 NTSC 6.2 PAL 6.60 NTSC 6.20 PAL 6.80 NTSC 5.76 PAL 6.80 PAL 6.65 NTSC 6.20 PAL 6.60 1500 MHz 1390 MHz 1350 MHz 1310 MHz 1250 MHz 1230 MHz 1210 MHz 1190 MHz 1170 MHz 1050 MHz 1030 MHz 1010 MHz PALAPA C2 113 E 4180 TPI Indonesia 4160 TV5 France 4140 TV Brunei 4140 SITV Singapore 4120 MTV Asia 4060 IVM Indonesia 4040 CNBC Asia 3980 CNN Int 3900 TV3 Malaysia 3880 ATVI Aust 3840 TVRI Indonesia 3840 TPI Indonesia 3745 RCTI Indonesia Vertical Horizontal Vertical Vertical Horizontal Vertical Horizontal Vertical Vertical Horizontal Horizontal Horizontal Vertical PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL 970 MHz 990 MHz 1010 MHz 1010 MHz 1030 MHz 1090 MHz 1110 MHz 1177 MHz 1250 MHz 1270 MHz 1310 MHz 1310 MHz 1405 MHz 6.60 6.60 6.60 5.50 5.50 5.50 5.50 6.60 6.60 6.80 6.80 6.80 6.60 6.60 6.80 6.80 6.80 6.80 6.2/6.8 6.60 right-hand struts have an “L” and “R” punched into the rounded end. We’ll leave you to work out which of these is the left and which is the right. Fit the two horizontal struts first. In all cases the square end goes to the reflector and the round end to the appropriate holes on the feedhorn bracket. Finally, bolt the bottom strut to the dish (again, the square end). The top end of this strut also connects to the feedhorn bracket but it goes to a tapped mounting hole at the bottom of the bracket. Some of the smaller nuts and bolts required may not be supplied – you may find them in your junk box or in worst case, spend a few cents at your local hardware store. The assembly of the dish is basically complete but you will obviously need some form of secure, rigid mounting post or mast. Keep in mind the wind loading of a 90cm dish not too far off vertical! Ideally, you want a 2-inch (50mm) OD galvanised pipe, about 3.5 – 4 metres long. The bottom end of this should be either cemented into the ground (at least 500mm or so) or securely bolted or clamped to some very firm support structure. The distance off the ground is not critical but if it is at all high off the ground, it should be quite high: high enough so that even a superleague basketballer can walk under it without cracking open his skull! For the moment, tighten the U-bolt nuts only enough to allow the whole assembly to stay in position on the mast but be rotatable. Later, when you finally tighten the U-bolts they should be very tight so that the dish is secured very firmly. The dish will want to swing away from the wind like a weather vane so these bolts must ensure that it cannot! Don’t worry just yet about any adjustment to the dish – just aim it in a basic east/northeast direction before you partially tighten the U-bolts. The feedhorn/LNB bracket bolts are still only finger tight – that makes it easier to adjust polarity if necessary later. The dish assembly is now complete but you may wish to cover any gal-plated bolts in silicone sealant for more protection against rust. Don’t seal the U-bolts or feedhorn bracket bolts; you need to aim the dish first. Connecting it up We’ll assume you have made up a suitable length of high quality, 75-ohm coax. RG-6/U is normally used for satellite installations – normal RG-59 TV cable has too much attenuation at the very high frequencies involved. The length should be enough to easily reach from the dish to where the receiver will be placed, without any “trip traps” (ie, lengths running above the ground where they can be tripped over!). F connectors are used on both the feedhorn and receiver so you’ll need three of these. F connectors are available in screw-on or crimp-type (which require a special crimping tool). All of these items are available at most electronics stores or satellite specialists. F-male to RCA-female adaptors are also available if you want to use a standard video-type lead. (Av-Comm Pty Ltd has RG-6/U coax for $1.00 per metre and F connectors for $1.39 each, both inc GST). Screw one end of the F connector into the receiver “RF in” socket and the other end into the LNB socket (on the back). LNB power, by the way, is supplied by the receiver down the coax. JULY 2000  15 Elevation angles (in degrees) of a prime focus dish to the 160°E Optus B1 satellite from Australia. If your town isn’t on the map, you will need to extrapolate a little. You’ll also need to calculate the angle for the 18° offset dish we’re using (subtract 18 from your location’s true elevation angle). In the final event, though, trial and error can be used to get the best result. 75 70 65 60 55 50 45 25 Because the output of the receiver is video and audio, your TV receiver will need video and audio inputs (most modern ones do). Alternatively, connect the receiver via the video-in and audio-in sockets on your video cassette recorder. You could also buy or build an RF modulator. Dish alignment Aligning the dish involves a bit of knowledge which you may or may not have yet! Basically, there are just a few of things you need to know. First, the output of the LNB occupies a band of frequencies between 950MHz and 1450MHz. Second, the polarity of the signal from the satellite can be either horizontal or vertical (sometimes both) and the way to adjust this is simply to rotate the feed horn/LNB in its bracket through 90°. Finally, the dish needs to be aimed quite precisely in the direction of the satellite. This involves two adjustments which themselves depend on where the dish is installed – the direction itself (also called the azimuth) and also the elevation of the satellite above the horizon. Azimuth is set by simply rotating the dish on the pole; elevation is set by adjusting the large screw thread on the mounting bracket so that the correct angle of elevation is achieved. (The type of mounting bracket fitted to the dish is called an Az-El bracket because it allows adjustment of both). There is another slight wrinkle: remember we said before that this is an offset dish. Normally a dish is aimed directly at the “bird” along its parabolic axis but an offset dish needs to be aimed as if were part of a larger dish (which in theory it is). For example, we want to aim at the 16  Silicon Chip 30 35 40 Optus B1 satellite (the one with most analog signals on it!) located at 160° east. The calculated angle of elevation for Sydney is 49.5° (this is derived mathematically). As the offset angle of the dish is 18°, the actual elevation of the dish is 31.5° (the angle between the vertical backing plate and true vertical). A large protractor and plumb bob is handy to get this angle right. If you’re in Woop Woop, make the appropriate adjustments to this angle. (Oh, Woop Woop isn’t on the map? Choose a nearby town or city and use that. You may need to extrapolate slightly). Firing it up Knowing all this, it’s time to aim the dish. We’re going to cheat a bit by using the receiver as a signal strength indicator. The signal level meter reads from 0 to 99, with the higher the figure the more signal being received. By tuning the receiver to a known frequency (see table 1), and setting the LNB polarity we can adjust the dish for correct alignment. The LNB has a label attached to one side – when this label faces up, the LNB is vertically polarised. The digital frequency readout on the receiver (accessed when you press the “tune” button) is a 3-digit figure which is actually the frequency in MHz or, if that figure is between 000 and 450, the frequency without a “1” in front of it – eg, if the readout says 955 it is 955MHz; if it says 245 it is 1245MHz. Set the elevation as detailed above and aim the dish as close as you can to where the satellite should be. This may require a compass and an accurate local map to get the angle correct but in general, close enough should be good enough to find some sort of signal. Once a signal has been found the dish can be aimed properly. This can take some time for the first time user but then that’s part of learning about satellite TV. For those who find the job a bit too time consuming, a simple signal strength meter can be purchased, as can an elevation meter, used for setting the dish elevation. Of course a plumbob and a protractor can also be used for this purpose. Once the elevation has been set, all that is necessary is to pan the dish around towards magnetic north until some sort of image is seen. Mounting the dish on a ground-mounted pole makes this procedure much easier. When a signal is received the dish azimuth, elevation and the LNB polarity can be peaked for best picture. At the same time the channel can be entered into the receiver’s memory by pressing the “channel” button, selecting an unused channel and then pressing “store”. Next time you want that satellite signal, it should still be there. So now you’ve made your first, albeit small (and low cost – especially low cost!) steps into the fascinating world of satellite TV. You’ll agree – it’s SC out of this world! WHERE DO YOU GET IT? This system is only available from Av-Comm Pty Ltd, 24/9 Powells Rd, Brookvale NSW 2100, (phone 02 9939 4377) for $49.95 including GST. Freight is additional (due to the size of the dish the goods would normally be sent by road). All dishes and hardware are as described and photographed; receivers are from the Scientific Atlanta 9600 series with minor differences between models. Orders will be filled on an “as received” basis until stocks are exhausted; specific receiver models cannot be requested nor can you order individual components from these systems. If you want only the dish, for example, it will still cost you $49.95 – and you're going to get a bonus receiver and LNB! The systems are all used and are sold “as is”, and there is no guarantee (although all systems were working at time of withdrawal from service). * Garry Cratt is the Technical Director of Av-Comm Pty Ltd.