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International satellite TV part 2. . . by Garry Cratt* Last month we discussed the basic principles of satellite TV reception, equipment required and the type of free-to-air programming that is available. This month we explain, in detail, how to install your own C-band (free-to-air) system. T he most important aspect of installation is dish placement. Obviously the dish must be able to point in the right direction to receive a satellite signal. With satellite dishes, “near enough” is most definitely not “good enough.” An error or 1°– or even less – can make all the difference on Earth (or off it!). The “view” to the satellite must be clear of all obstructions. Generally this means locating the dish away from trees, fences and buildings that might obstruct the line of sight to the satellite. As we mentioned last month, a dry tree usually makes only a marginal difference to satellite reception. The smallest rain shower, though . . . In order to find the best location, a decision has to be made as to which satellite(s) are to be received. The pointing co-ordinates for the desired satellite can be determined mathematically. These days, computer software makes this task relatively simple. We’ll look at software shortly. Azimuth and elevation The dish pointing co-ordinates will comprise two parts: an azimuth bearing, or the direction the dish must face to point at the appropriate satellite (for Australia that’s somewhere between 270° and 90°) and a value of dish elevation, or the angle between the vertical and the axis of the parabolic dish. At the equator, the dish points straight up but the angle increases as you get further south. Typical values for the most popular satellites and capital cities are shown in Table 1. That’s all the information you need to point your dish for a single satellite. Many people, though, want to look at a range of satellites. As all geo-stationary satellites are located above the equator and as the earth is round, the satellites aren’t in a straight line across the sky; rather they follow what is known as a geostationary arc. To view more than one, a motor is attached to the dish, designed to follow the curve of the arc. It is important to locate the dish so that all wanted satellites are visible to the dish at its extremeties of travel. A motorised installation is a bit beyond the scope of this article – that’s when you really do need professional STEP-BY-STEP: Putting in your own C-band system Open up the box of accessories which is supplied along with your dish box. You should find a set of instructions (which will vary from gibberish to excellent, depending on the brand of your dish – and even then not always constant), a plastic bag of nuts and bolts and a mounting plates. Along with the four dish panels (petals), you should get four feedhorn struts (inside the long box) and an LNB cover. www.siliconchip.com.au January 2003  7 help. So we will concentrate on viewing the signals from just one satellite. Councils and neighbours Most local councils now require a development application to be submitted for the installation of any satellite dish over 1m in diameter (some councils even smaller) and it is wise to check your local council’s policy. It’s also good policy to install the dish where it will have the smallest impact on the neighbours. While it might be possible to install the dish in a location not visible to the neighbours (or council), it should be remembered that councils can issue demolition orders for illegally erected satellite dishes (especially big ones!). One other point about neighbours: it’s amazing how paranoid some can get about those nasty microwaves jumping off your dish and curdling the milk in their fridge, causing untold cancers and even rotting the wooden legs on their tables and chairs. Of course, none of your assurances that it is for receiving only, that it doesn’t emit any microwaves, will satisfy them. One bloke we know finally placated a whining, threatening neighbour by telling him he was actually doing the whole neighbourhood a favour, collecting all the stray microwaves from space in his dish and piping them away. The overall result was less harmful microwaves in the neighbourhood, not more. Yes, it is stupid. But most people are when it comes to things they don’t understand. (And yes, the neighbour swallowed it hook, line and sinker). Site survey Assuming a position can be found that is both unobtrusive and has a clear view of the sky, the next step should be a site survey. Professional satellite companies always perform a site survey to ensure that there is good access to the satellite signals and just as importantly, that there is no terrestrial interference to the desired satellite signals. Unfortunately, C band (3.4-4.2GHz) is shared with terrestrial microwave services. Such services can be the source of interference and in some cases, completely prevent the reception of satellite signals. The site survey is done using a small (1.2m) dish with LNBF and a spectrum analyser. By pointing this small dish using the correct azimuth and elevation values for the desired satellite, the satellite signal can be verified and any interference can easily be seen. Dig your post-mounting hole deep enough to accommodate half the post length. For a 2.4m dish, that means 1.2m concreted into the ground. Standard mounting pipe is galvanised 76mm (OD). When you concrete in the post, it is vital that it be exactly vertical AND it stays that way until the concrete has well and truly cured. We normally use standard concrete, not quick-set, because it gives a stronger job. 8  Silicon Chip The table at right Pointing data for major Australian and S-E Pacific capitals. The figure immediately after the city is its magnetic deviation, while the figures underneath are its exact location (usually the major airport). These are given for those who wish to use dish pointing software. To use this chart, select capital city, then satellite number from list below. First data line is magnetic azimuth, second line is elevation. The main satellites listed are prime signal sources. The other satellites (listed underneath) have marginal footprints and may also be received on an itinerant basis. N/A means that the particular satellite is below the horizon for that city and is therefore unviewable. Even though this size dish is too small to connect to a digital satellite receiver for decoding, it allows the satellite signals – and any interference – to be viewed on the spectrum analyser. Where a dish is not available, even using a standard LNB to detect interference is better than no check at all. Where interference is detected, it can sometimes be eliminated by using the building itself as a shield. Where a satellite dish is to be installed in a location where there is known interference (eg, near airport radar), the value of using quad shielded coaxial cable can be appreciated. This simple step (choosing quad shielded over the cheaper dual shield) can mean the difference between perfect reception and no reception. In extreme cases, the coaxial cable can be run inside steel water pipe for even greater immunity to an interfering RF field. Now we are not expecting you to own a spectrum analyser but you may be able to find a local satellite TV company who will do this for you, albeit at a price. Digging the hole The most common installation and perhaps the most manageable is the backyard pole mount. There is one logical rule that applies here: whatever length of pipe that is above the ground should also be below the ground. This means that if you plan to install a 2.4m (diameter) dish, you’ll need to leave a length of pipe at least half the diameter of the dish (1.2m) protruding out of the ground and another 1.2m buried in the ground. So it’s pretty easy to remember – mounting pipe length equals dish diameter. Butt up two dish panels and finger-tighten just the outermost and innermost bolts with a flat washer under every bolt-head and nut. www.siliconchip.com.au www.siliconchip.com.au JANUARY anuary 2003  9 276 29.2 266.1 5.2 267.3 5.8 275.3 27.1 N/A N/A 266.0 4.1 273 18.8 N/A N/A N/A N/A 269.1 7.2 280.1 15.8 267.8 5.6 278.8 14.2 N/A N/A Azimuth Elevation Azimuth Elevation Azimuth Elevation Azimuth 273.6 Elevation 7.7 Sydney (12.6E) Canberra (11.9E) Adelaide (8.0E) 273.3 9.9 306.8 35.3 270.1 6.8 272.0 8.4 304.9 33.8 268.6 5.4 N/A N/A Azimuth 298.0 Elevation 27.4 N/A N/A Azimuth Elevation Perth (2.5W) 1. 2. 3. 4. 5. Azimuth Elevation N/A N/A 263.1 4.1 268.1 17.2 N/A N/A 273.4 10.0 311.4 38.7 276.5 13.4 283.3 19.4 271.9 10.8 270.0 9.5 268.3 9.2 277.5 33.9 83.0   4 261.4 3.0 266.4 21.8 272.4 35.6 260.2 4.0 287.9 22.0 334.6 49.2 290.3 26.6 298.0 32.9 284.6 24.7 282.0 23.8 278.3 24.8 286.7 52.2 100.5   5 287.6 35.8 292.8 33.5 296.0 34.0 312.0 41.1 302.8 35.0 354.7 52.7 300.2 29.7 268.5 13.8 277.2 49.0 269.6 34.9 281.7 29.2 286.0 27.7 288.8 28.6 303.2 36.4 295.0 30.1 343.0 51.1 292.6 25.2 263.4 7.9 274.0 40.9 267.6 27.0 265.7 14.9 300.3 64.8 291.0 57.4 263.1 7.7 113.0   7 105.5   6 Satellite Number Index – with type and launch date 6. Asiasat 3, HS 601HP 1999 11. Optus B1 HS 601 1992 Panamsat 10, HS 601HP 2001 7. Palapa C2, HS 601 1996 12. Optus A3, HS 376 1987 Apstar 2R, FS 1300 1997 13. Panamsat 8, FS 1300 1998 Thaicom 3, Spacebus 3000A 1997 8. JCSat 3, HP 601 1995 9. Measat 2, HS 376HP 1996 14. Panamsat 2, HS 601 1994 Insat 2e, ISRO 1999 10. Optus B3, HS 601 1994 15. Intelsat 701, FS 1300 1993 Asiasat 2, GE 7000 1995 (18°S, 178°E) Suva (12.7E) N/A N/A N/A N/A (9°S, 156°E) Honiara (9.2E) (9.5°S, 147°E) N/A N/A N/A N/A N/A N/A Azimuth 265.4 Elevation 2.8 Pt Moresby (6.6E) (37°S, 175°E) N/A N/A 267.2 12.7 266.8 10.6 Azimuth Elevation Auckland (19.4E) Azimuth Elevation N/A N/A N/A N/A N/A N/A Azimuth Elevation (43°S, 147°E) Hobart (14.7E) (32°S, 116°E) (38°S, 145°E) Melbourne (11.5E) (35°S, 138.5°E) (35°S, 149°E) (34°S, 151°E) (27.5°S, 153°E) Brisbane (10E) Azimuth Elevation Darwin (3.5E) (12°S, 130.5°E) 78.5   3 76.5   2 68.5   1 Orbital Location (°E) Satellite No. 272.0 29.7 275.6 51.1 289.0 65.1 280.1 25.4 318.1 36.8 024.2 50.5 321.9 42.8 333.8 47.9 313.8 43.3 309.9 43.4 303.5 47.7 344.0 75.1 128.0   8 294.6 56.7 327.0 77.8 036.9 74.7 311.1 42.8 358.0 39.7 059.9 33.1 006.1 44.7 020.6 45.4 359.4 48.4 356.0 50.2 355.3 57.7 62.1 57.4 156.0    10 300.7 60.0 349.7 78.8 047.7 71.3 316.9 44.4 003.6 38.8 063.4 29.9 012.1 43.5 026.3 43.5 006.0 47.4 003.0 49.4 003.7 57.0 65.6 53.2 160.0   11 308.0 63.1 012.8 77.9 055.0 67.4 323.1 45.7 009.1 37.7 066.7 26.7 017.8 41.9 031.6 41.3 012.3 46.0 009.6 48.2 011.6 55.6 068.4 49.1 164.0   12 312.3 64.4 022.4 76.9 057.7 65.3 326.2 46.2 011.7 37.0 068.2 25.0 020.5 41.0 034.1 40.1 015.3 45.2 012.8 47.5 015.4 54.8 69.6 47.0 166.0   13 319.5 66.1 034.0 74.8 061.2 62.2 331.1 46.7 015.6 35.8 070.4 22.5 024.5 39.5 037.6 38.2 019.2 43.9 017.4 46.2 020.6 53.3 71.3 43.8 169.0   14 LM-1, A2100AX 1999, 75 E Gorizont 28, NPO 1993 96.5E Apstar 1A, HS 376 1994 138E Apstar 1, HS 376 1996 138E Agila 2, FS 1300 1997 146 352.7 68.6 056.2 64.4 069.2 50.4 349.3 46.8 028.6 30.6 077.6 13.3 037.3 33.1 048.9 30.5 033.6 37.6 032 40.0 036.6 46.2 76.0 32.2 180.0   15 Gorizont 33, NPO 2000 145E ntelsat 802, GE 7000 1997 174E Intelsat 702, FS 1300 1994 176E Other itinerant satellite source (craft, launch date & position) 285.5 49.4 298.3 71.9 358.8 78.8 300.6 38.8 346.3 40.5 051.9 39.2 353.3 46.1 008.0 16.1 345.6 49.0 341.7 50.4 338.1 57.4 051.9 65.2 148.0   9 Table 1: Dish Pointing Guide for Capital Cities In practice its best to add 100mm or so out of the ground, so that even if the dish is tilted down for maintenance (rarely required), the lower rim of the dish cannot quite touch the ground, avoiding any possibility of damage. For mounting most 2.4m dishes, 76mm OD (outside diameter) This magnetic mount Anglemeter pipe, available from has 0.1° accuracy and a large dial larger hardware and face, allowing dish elevation to be plumbing stores, is read directly. used. For a few dollars more the store will even cut the pipe. In fact, it’s quite likely that you will be buying an offcut length anyway, as pipe tends to come in 6m lengths. Dig a hole at least 300 x 300mm, 1.2m deep and stand the pipe vertically in the centre. To keep the pipe vertical, wedge bricks, rocks, etc between the pipe and the wall of the hole, and check that the pipe is perfectly vertical by using a spirit level. Check the alignment at two positions 90° apart around the circumference of the pipe. In some circumstances it will be necessary to brace the pipe with two “starposts” or similar. A 300 x 300 x 1200mm hole is a little over 0.1m3. You can either use ready-mixed concrete or mix it yourself. For the latter, you will need four bags of standard concrete mix. (If you wanted a really strong mount, a 440 x 450 x 1200mm hole will take about 0.25m3 of concrete; 10 bags). Pour the concrete into the hole until it reaches a level 50mm below the ground level. This allows enough room for topsoil to allow grass to grow under the dish. Leave the concrete to set for two days, ensuring that the pipe remains untouched for that period (that includes making sure the kids don’t come out and give the pole a jiggle to see if it has set!). You might be tempted to use rapid set concrete but for maximum strength, ordinary concrete mix is used and allowed to dry normally. If you are digging the hole in an area comprised mainly of backfill (ie, low density soil) it may be necessary to weld a piece of flat bar across one side of the bottom end of the pipe, to ensure the pipe remains bonded to the concrete. A larger hole would also be more prudent. Repeat for the second pair of panels. They will happily stand up like this if there is no wind. But don’t risk it in ANY breeze! Sit both halves on a milk crate or small garbage bin and bolt them together. Now insert the missing bolts and tighten them all up. 10  Silicon Chip Dish assembly Once the pipe has been set in the ground, the dish can be assembled. Most mesh dishes are supplied as four pre-assembled panels which must be bolted together to form the parabolic reflector surface. Also supplied are four steel or aluminium tubes called “feed struts”. These hold the feed horn assembly at the focal point of the dish. In addition, there is a dish mount. This is the mechanical assembly that connects the reflector to the pipe. It is very cleverly designed so that elevation, azimuth and declination can all be separately adjusted. This is necessary for a motorised dish system, where a single motor makes the dish track in an arc, not a straight line!! All dishes come with some instructions. Depending on the brand, they may be very comprehensive or almost non-existent. Here are some “generic” instructions based on our experience. Much of the assembly can be performed by one person but several steps require at least two, if not three people. The main thing to remember is that the performance of the dish is dependent on the accuracy of the surface. So dents and rips in the mesh, apart from not looking at all aesthetically pleasing, will cause a reduction in dish performance and should be avoided at all costs. Even small dents can cause significant degradation and sometimes mean the difference between a good picture and a noisy (or no) picture. Take two of the dish panels (also known as quadrants) and stand them on their edge. Provided there is no wind (!), and the surface is flat (a concrete driveway is often useful) the panels will stand on their edge, the curve of the panel preventing it from falling over. Butt up the two panels and insert just the outermost and innermost bolts. Use a flat washer under every bolt-head and nut to prevent crushing the aluminium ribs of the dish panels. Do the nuts up “finger tight”. Place this “half dish” assembly to one side and make another half dish from the two remaining mesh quadrants. Once both halves of the reflector have been assembled, lie them face down on a horizontal surface (perfectly flat if available) with an inverted plastic garbage bin (or something similar) supporting the centre of the dish while you assemble it. www.siliconchip.com.au Then butt the two halves together and insert the outermost and innermost nuts and bolts. Do these up finger tight. You should now have a reflector lying face down on the ground. Insert all bolts and nuts (don’t forget the flat washers), working from the perimeter of the dish to the centre in a clockwise direction, tightening them with two spanners as you go. There are four mounting holes for the dish mount, so leave them vacant. Don’t forget to tighten the nuts you originally had only finger-tight. Find an assistant, then carefully pick up the reflector and turn it over so it is lying face up. Be very careful if there is any wind: even a mesh dish can get away from you. The feed struts The next step is to bolt the feed struts onto the feedhorn. Do this a short distance away from the reflector to eliminate the possibility of accidentally piercing the reflector mesh. The feed struts should be spaced 90° apart and are secured to the feed ring using four bolts and nuts. Using that same friendly assistant (or two of them if available), pick up the feed assembly complete with struts, and carefully position it over the reflector, making sure that none of the struts damage the mesh. Two people can hold up the feed assembly (each holds the assembly by two struts), while the third person inserts a bolt, washers and nut, at the location point on the reflector. You should now have a reflector lying face up, with four feed struts bolted to the rim, holding the feed ring at the focal point of the dish. As soon as the feed assembly is secured, there is a noticeable improvement in the rigidity of the entire assembly, as it is secured in both axes. The dish mount The next step is to place the dish mount on the pipe protruding from the ground. As long as the pipe does not protrude more than about 1.5m, one person can generally lift the mount onto the pipe. But it’s always better with two. That mount is heavy! First a few precautions: Ensure that the securing bolts on the outside of the mount sleeve (designed to clamp onto the pipe) are loosened off so that the mount can slide onto the pipe. Fix an azimuth bar (supplied with the dish) to lock the east /west movement of the mount. This prevents the mount rolling around the horizontal axis as you lift it onto the pipe. Once the mount has been lifted onto the pipe, rotate it Hopefully your completed dish looks something like this! Be even more careful now you’ve got this far; from now on it’s a 2-man job! www.siliconchip.com.au such that it is in a position where the dish can be lifted (by two people) onto the mount, then tighten up the mount securing screws to hold it solid. This is not the final position of the dish, merely a convenient position to finish the assembly. Adjust the mount elevation to about 30°. This will enable you to lift the reflector up against the mount, rather than lifting it above the mount. Up she goes! We now need to lift the reflector (dish) onto the mount, orienting it so that the four lugs on the mounting ring correspond with the four double ribs formed by bolting the quadrants together. We also need to consider the LNB securing bolt on the feed horn. This needs to be facing downwards (towards the ground), so it is easier to adjust once the dish is mounted. With the mount clamped to the pipe, the azimuth bar in place, and using two or three people, carefully lift the upturned reflector and feed assembly onto the mount, positioning the four lugs on the mount and corresponding double ribs. While one person holds the reflector in place against the mount, another person must insert the four securing bolts. It’s necessary to operate from behind the dish to do this, inserting the uppermost bolts first. Don’t forget the flat washers under the bolt heads and nuts. Once the two uppermost bolts have been inserted, the reflector will sit on the mount without support, while the remaining two bolts are inserted. Now tighten all bolts, making sure the mesh is not damaged by the action of the spanner against the securing nuts. The dish is now ready to have the LNB added and to be pointed towards the satellite. Pointing the dish There are four critical parameters that must be determined for every dish installation. They are dish azimuth, dish elevation, LNB orientation and dish focal point. Fortunately, the focal point is almost always determined by the length of the feedarms. When the feedhorn/LNB is set in correct position, no further adjustment should be needed. The azimuth and elevation of the dish need to be mathematically calculated. All satellites are given an orbital location, which in the case of Asiasat 2 is 100.5° east longitude. This means that the satellite is located 37,000km Connect the feed struts to the LNB hardware – do this away from the dish so you don’t risk damaging the dish mesh. January 2003  11 This satellite signal indicator comprises a broadband amplifier and diode detector, intended to be used at the dish to assist in signal peaking. up, at the intersection of the equator and 100.5° east line of longitude. From a map you’ll see that this location is over Indonesia. For Sydney, even the most rudimentary geography indicates that the dish will be facing somewhere in the western sky. Ummmm – west – that’s away from the coastline in Sydney. Fortunately, there are plenty of computer programs available that simply require the latitude and longitude of the dish, together with the longitude of the satellite.You can find a variety of software on the net, some of it freebies. One such program, GEOSAT.EXE, is one we use at Avcomm Pty Ltd – in fact, we wrote it! Alternatively, a quick “Google” will find any amount of similar programs, such as SMW Link, from Swedish Microwave AB (www.smw.se/smwlink/smwlink.htm). Make sure you get the latest version (3.05) because earlier versions had a southern hemisphere calculation bug! But it’s often even easier than that, because most modern receivers have a dish pointing menu, where these parameters can be entered to calculate the desired azimuth and elevation of the dish. has at least one (and usually more) latitude and longitude reference on the side. Alternatively, if you have ’net access you can Google something like “latitude longitude Gulargambone” – especially handy if you happen to live in Gulargambone. You should find several websites which will give you the exact (to the minute and sometimes even second) location of your town/city, especially if it has an airport. Beware, though, in big cities, the figures are likely to be that of the main airport – and if you happen to live on the opposite side of the city, you could be out by as much as a degree or so. One further alternative is a very useful book called “The Dick Smith GPS Guide”. Available from DSE stores or Australian Geographic, this lists over 16,000 locations in Australia and the corresponding latitude and longitude. If using this book, its important to remember that most dish pointing programs require latitude and longitude in degrees and tenths of degrees (eg, 34.5) not in the format provide by the book: degrees, minutes, seconds (or 34°30’0”). Fortunately the book does have a conversion chart – and even mental calculations aren’t rocket science. (Rocket science? Satellites? Get it . . . ? Oh, don’t bother . . .) Azimuth You probably don’t know the exact latitude and longitude of the dish site. To work out the exact (to the minute) location, we normally use either a good map or GPS. Detailed topographic maps of your area will enable you to extrapolate your exact location because the grid always One further parameter is required to calculate the dish azimuth – remember, that’s the direction it points. But there is a little wrinkle here called magnetic variation. That’s the difference between what you read on a compass as north, and true north (ie, lines of longitude from pole to pole). Magnetic variation varies all over the place depending on the specific place you are at, while computer software invariably works on true north – and you have to add or subtract the local magnetic variation to achieve the desired result. Magnetic variation can usually be found for any particular location on a specific map called a “WAC” (World Aeronautical Chart), often used by pilots. These charts are available at all good map shops and pilot supply centres. Magnetic variation is also listed on topo maps. A point to note: as well as varying by location, magnetic variation changes over time. The map may give a misleading figure if it is more than a few years old. Once again, Google is a great way to find out magnetic variation (which is, by the way, also known as magnetic declination). Google ‘“magnetic variation” Sydney’ and you’ll find several sites giving the result: 12.6° E. Very carefully bolt the struts onto the dish using the mounting holes provided. Place the dish assembly somewhere safe. Here’s what the dish mounting hardware looks like straight out of the box (albeit photographed here almost upside down). The cylindrical section with the four bolts at right actually points vertically down (it’s the bit which slips over the top of the in-ground 76mm pipe “post”). Those bolts are tightened against the post to ensure the dish cannot “windmill” in strong winds. The ring (on the ground in this pic) is the part which bolts on to the assembled dish. Where am I? 12  Silicon Chip www.siliconchip.com.au Recalling the rhyme “east is least” reminds us to subtract lines of magnetic variation marked “E” from the calculated true azimuth. In the case of Sydney the magnetic variation is 12.6° E, so we need to subtract 12.6° from the calculated “true” azimuth. The magnetic variation for Perth is around 2.5° W, so we must add 2.5 to that “true” azimuth. Elevation The dish pointing software calculates elevation directly in degrees. Fortunately, this is much easier to measure and set. The simplest method is to use a protractor and a piece of cotton and a weight but if this is too much trouble a simple analog inclinometer can be purchased reasonably cheaply. This type of instrument has an oil filled chamber with a pivot and a counterweighted pointer. A far more sophisticated digital instrument is used by professional installers, as the dish geometry of a motorised system must be set to within one tenth of one degree, or six minutes. The reality is that most home installers will be able to set up a system to look at any single satellite but without sophisticated measuring equipment, the alignment of a motorised system will require professional help. Where’s the satellite? Now that we have been able to work out the dish azimuth and elevation, we can get to work. Let’s use the example of Sydney and the Asiasat 2 satellite. We know the latitude of Sydney is 34° south, and the longitude is 151° east. We also know that the longitude of Asiasat 2 is 100.5° east. Our software tells us that the dish elevation must be 23.87°, and the true azimuth is 294.75°. Subtracting 12.6° from the true azimuth gives 282° magnetic. This is the required compass heading. A cheap and nasty compass won’t cut the mustard here: it needs to be a decent, fluid-filled model graduated in individual degrees. Good orienteering compasses are usually a reasonable compromise between cost and usefulness. Also remember when aiming a dish that the compass itself is likely to be affected by close metal (usually steel) objects. Just keep that in mind if your compass readings keep changing as you move about. The elevation is somewhat easier to set. Assuming the mounting pipe has no elevation (just like a dish standing on the rim), calibrate the inclinometer for zero degrees. Up the right way: the threaded rod in the centre of the pic adjusts the dish elevation, while the rod at right adjusts declination. www.siliconchip.com.au When you get really serious (!) this digital inclinometer has one degree accuracy and resolution. It’s a must for setting up motorised dishes. Place the inclinometer on the centre plate of the dish (from behind), so that the counterweight is vertical. The elevation of the dish can be directly read. Adjust the threaded rod until the elevation reaches 24°. This should be close enough, once the dish is pointed in the right direction, to acquire a signal. One tip – before setting elevation, run the spirit level over your pipe one last time to make sure it hasn’t moved before the concrete had a chance to harden. It happens! Installing the LNB Now is the time to install the LNB into the feed rings. Do this by slipping the LNB through the ring assembly, so that the front edge of the waveguide protrudes 20mm past the level of the concentric rings. Rotate the LNB so that the flat part of the housing is vertical. This is a good starting point for further adjustments once the system is operational. This brings us to the next point: how do we measure the signal? Fortunately, there exists simple in-line signal strength meters for this task. One popular (and economic) type is called, logically enough, a “Satellite Finder”. The meter has an input port that requires DC voltage from the satellite receiver and an output port that feeds that DC voltage to the LNB and reads the amount of signal being sent from the LNB to the receiver. Basically, it is a simple broadband amplifier and a rectifier driving an analog meter movement and a tone generator. As the signal gets stronger (as we peak up the dish), the meter deflection becomes greater and the tone gets louder. The meter also has a sensitivity adjustment. Now, having set the dish elevation, set the LNB orientation and calculated the magnetic azimuth of the dish, rotate the entire reflector and mount assembly on the pole The completed mount. The solid bar (arrowed at left) locks the dish azimuth (set by rotating on the pole). This bar can be replaced by a suitable motor to enable the dish to track any number of (viewable) satellites. But for single-bird systems, this bar is bolted in place as shown here.  January 2003  13 until it points in the desired direction. At this point, connect the LNB to the signal meter and the signal meter to the receiver via short lengths of coaxial cable. Because you are not trying to display a picture right now, you don’t need any monitor so setup is most easily done close to the dish with the receiver on a suitably long power cord. Adjust the meter sensitivity to maximum and turn the receiver on. As the dish assembly is rotated on the pole, the signal strength meter will begin to respond. As the meter reaches full scale, back off the sensitivity while continuing to move the dish, until the signal is peaked. Carefully adjust the clamping screws on the dish mount so that they are all tightened evenly, clamping the mount to the pole without causing any skew in the vertical plane. It may be necessary to optimise this adjustment several times. Once this has been done, the elevation adjustment should be optimised for maximum signal, by slowly turning the elevation rod. When this is peaked, lock it in place. At this stage, select the desired channel on the satellite (most receivers come pre-programmed) and carefully rotate the LNB (with the meter still connected) until the signal is peaked. This adjustment will only be in the order of 10-15°. Making adjustments greater than this will mean the LNB is peaking on signals of the opposite polarity, as most satellites have signals of both horizontal and vertical polarisation (and sometimes on the same frequency). This adjustment is called cross polarisation optimisation. Connecting up your system. Like most pieces of audio visual equipment, a digital satellite receiver has several different outputs for connection to a TV set, VCR or hifi system. For best results, especially where a recording facility is desired, it is normal practice to connect the direct line audio and composite video outputs from the satellite receiver to the VCR and then use either the RF or (again preferably) the A/V output of the VCR to connect to the TV set. Most satellite receivers have two or more A/V outputs, allowing separate connections to a hifi system for enhanced audio. However, many overseas stations broadcast in dual mono and often in different languages. In some cases the redundant audio channel is used to carry a separate radio service. Place the dish on the mount. This is definitely a two-man job (the missing man in this picture was the photographer!) The double edges (joins between the dish panels) slot into the U-shaped brackets on the mount. Place the upper-most bolts and nuts first. Some to-ing and fro-ing of the dish panels might be necessary to get the bolts to go right through the holes in the double-thickness joins. Make sure all dish panel and mounting bolts are tight. 14  Silicon Chip For this reason, satellite receivers allow the user to determine which output will be routed to the sockets on the rear panel. Assuming there is coaxial cable supplying TV wall outlets in several rooms in the house, the RF output of the satellite receiver can be combined with the existing internal TV cabling to provide a “satellite” channel. While the limitation of this system is that only one channel is fed into the system, it does mean that satellite TV can be enjoyed in many rooms. Anyway, you can only watch one channel at a time, no matter which room you are in! Channel surfers (or those with the remote control permanently super-glued to their hands) need not apply! If the ability to record is not required, best results are obtained by running the line audio and composite video outputs of the satellite receiver, directly in to a spare A/V input on the TV set. This is an easy way to switch from normal terrestrial TV to satellite TV. Most modern TV sets are multi-system, meaning they have the ability to convert an NTSC video signal into a PAL signal. If you don’t have one of these, and the station you want to watch broadcasts in the American (NTSC) video format, you may need a video systems converter. Countries using the NTSC format include USA, Canada, Mexico, Japan, Taiwan and Korea – in fact pretty well anywhere where there has been a US influence in the development of the country, use NTSC. All other countries use PAL these days (even digital signals from Russia use PAL!). PAL or Phase Alternating Line, is of course the system used for analog TV transmission in Australia. Analog converters start at $99, while fully fledged digital converters (that allow recording on a PAL VCR) range from $750 to $2000 for a top-of-the-line model (near broadcast quality). As a digital satellite system is capable of delivering very high quality video, the appropriate quality cables should be used. This means going to a reputable electronics outlet to obtain them. In the old analog days it might have been possible to put up with the video performance of audio cables, such as the inexpensive twin RCA-RCA types we have all seen. However, to preserve the quality of the video performance from the satellite receiver, it is important to use well-screened, moulded, three-conductor low capacitance cables, which can normally be identified by the larger There are four possible adjustments for maximum signal: azimuth, elevation, declination and LNB polarity/focal point. These must be set as explained in the text. In this shot, Erin is setting the elevation – the angle in the sky to which the dish points. Turning the elevation rod raises and lowers the top of the dish with respect to the vertical mounting pole. Azimuth is adjusted even more easily – by rotating the dish on the mounting pole. The focal point is almost always fixed. Don’t worry about declination unless setting up a motorised system. www.siliconchip.com.au A typical digital satellite receiver – in fact, this or one very similar is the one in the special offer at right. diameter of the video cable. The effect of using inferior cables will be colour smearing, ringing along the leading edge of the video and generally poor definition. Do I leave the receiver on? Most satellite receivers have a standby function, putting the receiver to sleep but allowing voltage up to the LNB. This has the effect of keeping the LNB stable and at a constant temperature. For this reason, it is wise to leave the receiver in the standby mode when it is not being used. This also eliminates the possible ingress of moisture into the receiver itself. Like all electronic equipment, keep the receiver well ventilated. This is particularly so when several pieces are stacked together in a typical hi fi cabinet. Spacing equipment apart with small blocks of wood can help in this aspect. Avoid the practise of some people (let’s not be sexist here) of putting doilies on top of the receiver (or VCR or CD or DVD or anything else for that matter) and putting a pot plant or vase of flowers on top, “to make it look more attractive”. Apart from the fact that this may well cover the ventilation slots and cause overheating, there is always the danger of the vase being knocked over and the internals taking an unwanted and probably highly damaging shower. For the same reason, empty video sleeves, CD/DVD/ cassette cases, etc, should never be placed on top of electronic equipment. SC EXCLUSIVE SPECIAL OFFER FOR S ILICON CHIP READERS Av-Comm Satellite Equipment has a very special offer, exclusively for SILICON CHIP readers: a complete, brand new, state-of-theart DIGITAL satellite receiving system ready to put together, connect up and turn on! Here’s what you get:  A 2.4m 4-panel mesh dish complete with all mounting hardware (except the post!)  A dual polarity, low noise, block downconverter (LNB)  A high efficiency feedhorn  A Digital Satellite TV Receiver with remote control, MPEG-2 and digital DVB compliant.  25m RG-6 (satellite grade) coaxial cable and two “F” connectors  An analog inclinometer  A “SatFinder” in-line signal strength meter Current Av-Comm catalog price for all this is $1450.00 – but until February 28 2003, if you tell Av-Comm you’re a SILICON CHIP reader, you can have the complete package for just $1295.00 – that’s better than 10% off. And remember, all this equipment is brand new, with full warranty. Order direct from Av-Comm (do not call SILICON CHIP!) Phone Av-Comm on (02) 9939 4377, fax 9939 4378, email cgarry<at>avcomm.com.au or use the special SILICON CHIP SYSTEM order form on Av-Comm’s website (www.avcomm.com.au). * Director, Av-Comm Pty Ltd The LNB is a friction-fit into the feed horn (at the junction of the struts). After fitting and connecting the coaxial cable, you need to adjust the LNB polarity for maximum signal by rotating it in the feed horn. You will probably need to re-adjust elevation and azimuth. To complete the job, run the coax down one of the struts and secure it with black cable ties (white ones will break down over time due to UV). Make a loop around the back of the dish and cable-tie the coax to the mounting post. www.siliconchip.com.au And now it’s finished. We’ve left the LNB cover off for clarity (quite often they are left off anyway!). The coax is connected to the LNB and secured to the strut and post – now it is just a matter of connecting it to your satellite receiver, tuning in the required channel and watching your satellite programs. After the dish has settled in, it might pay you to re-peak the azimuth, elevation and LNB output as previously detailed. But if you have wall-to-wall signal, it’s probably not worth the bother. Enjoy! January 2003  15