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An easy way to set the dish elevation |
| Your dish needs to be aimed in 2 different directions in order for it to point precisely at the Astra 2 satellite system: it needs to point to the correct compass bearing (the azimuth) and it also needs to point up at the correct angle (the elevation). The azimuth is relatively easy to achieve but the elevation of course is not. Even after using a dish for over 10 years, I still struggle to get it right. I recently heard from 2 people who had built very similar, and equally brilliant, methods of achieving it. |
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1. Bill Naulder's device Bill Naulder was the first to contact me and his technique so impressed me that I immediately implemented it for my own setup, so with his permission I have included it here. He bought a Silverline inclinometer (available from a number of places - just Google it, it's possible to get one for under £5 these days) and used the following technique to set it up. (There are also digital models which are more compact, but they're also more expensive. Take your pick.)
He bought a steel right-angle bracket from his local hardware store (OK then, B&Q!) and you should be able to see from the following pictures how he fitted it to the dish. The inclinometer has a magnetic base, so it can be placed on the bracket and removed when not in use. The bracket can also be removed from the dish when not required, though it could be left permanently in place. The precise method of fitting the bracket to the dish will obviously depend on the construction of your own dish. We leave that to your own ingenuity!
Now comes the calibration part, and it's really a matter of trial and error. It's also the trickiest part of the whole procedure but fortunately it only has to be done once. (It's worth taking a bit of time over because the usefulness of the inclinometer will depend on how accurate you get this initial setting.) First, find the elevation for your home locality, using say www.dishpointer.com. Then set your dish up at home until the alignment is correct and you have a good Signal Strength/Quality reading. Having done that, you simply have to bend the angle bracket in a vice until the inclinometer shows the same degree of elevation. Thereafter, all you need to do is find the elevation for any campsite you visit (using Dishpointer again) and adjust the dish until the inclinometer shows that angle. For when it's not convenient to access Dishpointer when on the move, Bill has printed out his own maps of Europe with elevation lines drawn on them. This map is shown for illustrative purposes only. It's assumed you'll create your own if you need one!
One further point. If your tripod isn't fully vertical, the elevation angle will alter as you turn the dish horizontally one way or the other. In an extreme case it might be enough to significantly shift the angle away from the optimal value. Therefore be prepared to check the inclinometer reading and readjust it if necessary. |
| 2. David Monkman's device
A few weeks later, David Monkman wrote to say that quite independently he had developed a similar device to Bill's. His has advantages and disadvantages so I'm presenting them here and it's entirely up to you which idea you choose. David's involves a lot more work to start with because the device has to be constructed. However it is then easier to calibrate and can also be used on different dishes.
It is made with 3 bits of 2cm section wood. Each of the two outer pieces has been drilled & grooved to become the other half of a sprung clothes peg. These 2 spring clip onto the dish rim. The 3rd piece is clamped between the other 2 by a bolt & is topped by a strip of steel to hold the magnetic base of the inclinometer. To calibrate the device, the inner piece that supports the inclinometer is held lightly & turned until the inclinometer shows the local elevatiion when the dish has already been well adjusted. The clamping nut & bolt is then tightened & the slope rechecked. Thereafter, no further adjustment is needed unless the device is used on another dish (see the next paragraph). After calibration the device is removed & stored for use on the next site. On the pictures above, it is just possible to see a score mark on each side of the centre section. This is there to allow for the device to be used with alternative dishes, eg a 60cm dish for the UK and a 100cm one for Europe, that might have different rim angles. After the dish has been aligned, the device is unclipped & stored. Initially, David's device used a protractor which was pinned to the centre section but when he saw Bill's on this page, he realised an inclinometer would be vastly superior. So that's when he fixed a steel plate to the top. This device is much easier to calibrate because it doesn't depend on the trial and error bending of the right angle bracket. On the other hand it does involve a lot more work constructing it in the first place. And there's one further advantage. Once the device has been calibrated and the dish elevation is at the correct level for your current location, the metal plate will be at the correct angle to point directly at the satellite. Thus you can use it as a line of sight to check for trees or other obstructions, and if necessary move the dish to another spot. Without it, it is virtually impossible with a solid offset dish to establish for certain whether an object is an obstruction or not. Bill Naulder's idea will work with a transparent dish but not a solid one unless the bracket can be fitted to the top edge of the dish. (In fairness I should point out that Bill did offer this as a possibility by cutting a slot in the top of his solid dish for the right angle bracket to fit into.) |
| 3. David Monkman's elevation fine
tuner This guy's obviously an engineer! He developed this mechanism using a turnbuckle (the type of gadget used to tighten fence wires) to raise or lower the elevation of the dish very accurately.  They come in a variety of sizes from M6 upwards but M8 or M10 is probably a good compromise between ease of turning and the range of elevation variation. They're not expensive and can be bought from Screwfix, for example, for under £2. The method of attaching the turnbuckle to the dish will obviously depend on the way in which any individual dish is designed but what follows is the general idea. It would be too complicated to cover all dish sizes and designs here, so you might have to experiment with different turnbuckle sizes and fixing mechanisms to achieve the best result.
These 2 pictures (with a 60cm and a 100cm dish) show the
turnbuckle in place. It allows the dish inclination to be smoothly, and
therefore very precisely, changed. It has a ring at the bottom & a
hook at the top end which is lashed with gardening wire to a bolt (see
the picture below). The ring is held with 2 nuts to a bolt fitted
through the dish holder. The outer end of the bolt was wrapped with self
amalgamating tape (not shown) to eliminate slobber at that joint.  The 100cm dish needed a further modification because it was too large for the original turnbuckle assembly. David had to replace the top section with a threaded rod in order to achieve the extra length. It can be seen in the 2nd picture above. If you go for this, you'll need to check that the section being replaced has the same thread (clockwise or anticlockwise) as its replacement. To operate the mechanism, the curved channels of the dish holder are silicone greased and the dish clamp is loosened just enough to allow it to slide when the turnbuckle is rotated. The turnbuckle is then rotated clockwise or anticlockwise to achieve the required lift. Once the dish is aligned on to the satellite, the dish clamp is tightened again. The mechanism allows for very precise adjustment of the dish elevation, enabling the dish to get the maximum amount of signal in marginal areas. Please note that this description is as comprehensive as I can make it, without actually trying it for myself (which I don't have time to do at present!). So if you don't understand any of it, I can't help you with any further advice! Meanwhile David says his next project is to develop a screwed adjustment for azimuth and he's been working on it for some years without success. He offers it as a challenge to anyone reading this webpage! |
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Bill Naulder's azimuth finder The device is remarkably simple, consisting of 2 lengths of wood, 2 non-ferrous metal strips and a marine compass (Bill's own is a Suunto Pilot, available as usual via Google). The lengths of wood are fastened together to form an inverted T which is then hung from the upper rim of the dish using the metal strips formed into a bracket as shown in the following pictures. On the top of the metal bracket is attached the compass mount. The compass mount is fixed permanently and the compass itself just clips into it as and when required. All the fixings are made using non-ferrous screws. The top section of the metal bracket doesn't need to be absolutely horizontal because the marine compass is self-levelling. (I need hardly add that the whole assembly just lifts off the dish when not in use.)
To use the finder, just determine the required azimuth from Dishpointer and swivel the dish till the required bearing lines up with the "Lubber line" on the compass (in the picture above, the lubber line is shown in red and the bearing is set to 145º). Bill points out that even non-ferrous dishes might have some steel components (eg the mounting bracket at the back) but that the compass mount is far enough removed to minimise the magnetic effect and in any case is easy to adjust. It is fixed on to the top of the assembly by means of 2 screws so the trick is to adjust the dish initially until the maximum signal strength/quality is attained. Then if the compass doesn't quite match your known bearing, the mount can be turned accordingly before the second screw is put in place. Thereafter, no further adjustment is needed. The one exception to the trivial effect of a ferrous material on the compass is of course the magnetic base of an inclinometer if used - which must be removed well away before using the compass! |
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Re-cabling a new caravan for satellite Monkton has a Bailey Pegasus which has an internal TV service point on the same side of the caravan as the mains/battery locker, but it's a small modification to adapt a caravan that has them sited on opposite sides. First he adapted the battery box by enlarging the cable entry hole with a round file. Then after considering the direction and route to the TV point, he drilled two 9.5 mm holes near the 230 volt connector for the mains cable (the precise location will depend on the route the cable takes after leaving the battery locker). Into these holes he put male/male sat connectors and nutted them into place, using silicone mastic on both sides, to keep battery generated hydrogen out of the caravan (I'd also recommend using self-amalgamating tape on the reverse side of the male/male connectors). At the TV socket area inside the caravan, he
installed a pair of cable tidy grommits for the fly
leads going to the satellite box (shown here: My preferred alternative is to fit a twin socket surface plate such as this one, simply because I prefer to disconnect the fly leads when we're on the road, rather than have them flapping around:
Both these items are available from suppliers such as Satcure (don't forget to pick up a discount e-voucher first from my Links page!) If the TV service area inside the caravan is on the opposite side from the battery locker, you'll need to drill 2 pairs of cable holes through the floor at each side of the caravan. Using caravan waterproof mastic at top & bottom, take the cables down from the locker and pin them using cable clips through more of the same mastic to hold them up to the floor. You'll have to route the cables appropriately depending on where the chassis members are. One final point. There might be an occasion when only one cable is in use (when you only want to use a basic satellite receiver rather than a twin-tuner recorder). To avoid the risk of getting the connections crossed and ending up with no signal, use 2 lengths of differently coloured cable and connect the colours to the left and right terminals both inside and outside. |
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