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March 22, 2007

Fine-tuning a motorised dish

by Analoguesat

Here are our Five Top Tips for fine-tuning a DiSEqC motorised setup.

This mini-guide assumes that you have already set up your mounting brackets/mast, motor, dish, LNB etc. and have managed to tune in a least a few satellites. Your setup is far from ideal though, right? Poor signal strength and quality? Missing some satellites? Read on…

First - Make sure you have read and re-read the Satellite Help guide to DiSEqC motor installation so that you not only follow the procedures required for first-iteration setup, but understand the theory behind what you are trying to achieve. Sometimes your brain has to seemingly work in four dimensions to calculate which tweak has to be made to your dish/motor to improve things!

Second - Mark everything before you start with a permanent marker. This way, the worst that will happen is you end up back where you started. Based on this premise, most anything you do should improve your arc-tracking!

Third - Only adjust one thing at a time. This is important, otherwise you will never know which adjustment had which effect. You are probably dealing with a multitude of minor errors, so you need simple solutions. The only exception to this is a combination of elevation and declination. If the OVERALL elevation of the dish is already optimal for a given satellite, then increasing one will mean increasing the other to stay exactly on-satellite. Don’t forget that an increase in declination is a downward tilt at the dish scale.

Fourth - Forget USALS. Use DiSEqC 1.2, because it gives you total azimuth control of the dish positioning. Once your dish tracking is near-perfect you can go back to USALS if you so choose, but once you have finished this process you may find that USALS will just not cut it any more.

Fifth - This is what the first four tips have been building up to. Draw a map. Yes, a map. Draw a map of the theoretical arc, and roughly mark onto the line all the satellites you think you should be able to receive. Now, start with your dish in the middle of the arc and peak the first satellites’ signal using just the motor via the receiver menus. Record the actual azimuth setting that gives you the peak reading (you should be using ‘GOTO x.x’ format commands).

Now flex the dish face up and down gently whilst checking the signal quality/strength on the receiver/meter. Note on your sketch whether the signal improves if you tilt the dish face slightly up or slightly down. Mark where the actual satellite appears to be on your diagram. Repeat this whole procedure (i.e. drive motor to peak signal, flex dish and then record results) for as many satellites as you can stomach.

Now, using this information, and the actual azimuth figures you also recorded, compare the results to the arc-tuning diagram here:

Satellite Arc Tuning

The more readings you take, the clearer the picture will be. Be scientific about it, and you should be able to identify one or more of the erroneous conditions indicated on the chart.

Finally, don’t be afraid to move slightly away from the indicated settings on your motor mount and dish scale. The stamped scale on some brackets can be well over a degree out, whilst some dish scales seem to make no sense at all. It’s also possible to have the mount slightly twisted on the pole, even if you have tightened the four nuts on the two U bolts equally. Remember - the alignment you have at the end of the theoretical phase is only a starting point for real-world fine tuning.

Patience will get you there in the end – good luck!

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