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Installing a DiSEqC motorised dish

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2 What Satellite & Digital TV

Installing a DiSEqC motorised dishIf you’ve already got a fixed dish it can be easily motorised with the addition of a DiSEqC motor and there are no extra cables to fit

The most popular route to a motorised system is to fix a DiSEqC 1.2 or USALS motor onto

an existing fixed dish wall mount and attach the dish to the motor. This gives you access to dozens of satellites without changing your dish, LNB or even the cable to the receiver.

There are several DiSEqC motors available for dishes up to 1.2m across (although use of a dish over 1m is not really recommended). All operate in much the same way and are fairly simple to set up.

How to fix the motor to the mountWith most fixed dishes (but not Sky

or Freesat minidishes) on a wall or patio mount, when you remove the dish you are left with a short vertical pole (usually about 2in diameter) attached to the wall or standing on the patio. This is all a DiSEqC motor needs.

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The mount pole must be sturdy – with the motor in place, there is a greater weight on the pole mount and as the dish will stand out from the pole, wind loading has more of an effect – and it is vital that it’s exactly vertical. You should adjust the fixings to ensure a spirit level or inclinometer used all around the pole shows that it’s plumb.

Now position the motor on the pole so that it points roughly south and tighten the U-bolt clamps to hold it in position.

How to set up the motor inclination angle

While some DiSEqC motors have the rotating spindle on which the dish is mounted pointing upwards, others are designed with this hanging below the motor. It makes no difference to the operation, and both types have the motor casing hinged within a bracket that clamps to the mount pole. Adjustment of this hinge alters the motor inclination angle and this should be set for the latitude of your site.

If you don’t know your latitude look it up in an atlas or mapping website and adjust the motor so its latitude scale is set correctly.

Now mount the dish onto the motor spindle in the same way it was once fixed on the mount pole. It’s important that the dish is aligned with the bend in the motor spindle. There is usually an index mark on the spindle to centre the dish U-bolt clamps on. Tighten these U-bolts fully as they will not need to be adjusted again.

How to set the motor’s declination angle

The mount’s declination is the small ‘downward’ angle that the dish makes with the motorised axis to account for the fact that the satellites are not infinitely far away. In the UK the declination varies from 7.3° at Lands End to 8° in Orkney. You can either estimate the value for your position, or simply assume that it’s 7.5°.

The declination is set using the dish’s own mount’s elevation adjustment. However, the bend in the motor spindle

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also produces a large downwards tilt of the dish, so it is nearer vertical because an offset dish (the usual kind used) is designed for a roughly vertical pole. The angle of this bend (the spindle offset angle) differs between motors and should be read from the motor’s instructions. It is usually 30° or 45°.

Calculate the dish elevation setting to accommodate this bend according to the formula:

And adjust the dish elevation to read the calculated value and lock off the adjustment carefully.

How to set the motor to find SouthNext, the whole motor needs to be

pointed accurately to South. The method is to set the motor to point the dish where a satellite is expected and then rotate the whole assembly on the mount pole until that satellite is found. Pick a satellite that’s reasonably close to South and easy to find. Hot Bird is often used.

With a standard DiSEqC 1.2 system you have to set the motor position by hand,

Elevation setting = pole offset angle declination

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Motorised fixed dish:The DiSEqC motor is fixed to the existing fixed dish’s mount pole

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Vertical poleIt is essential that the mount pole is accurately vertical for the motor to properly track the satellite arc

Existing dish on wall-fixed altazimuth mount

Same dish and wall mount with DiSEqC 1.2 motor

Check pole with a spirit level all

around and insert/remove shims on

the pole fixings to adjust to vertical

Brick

wall plug

washer/shimbolt

bracket

What Satellite & Digital TV 3

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using the receiver (connected with a co-ax cable to the Rec socket on the motor), driving the motor east or west until the pointer indicates the correct position. This is calculated with:

Again, if you don’t know your longitude look it up. Eastern longitudes are negative, western positive. Hot Bird is at 13°E so for, say, Birmingham (longitude 2°W), the motor is driven to 15°E (-13-2) read from the scale on the motor.

It’s easier with a USALS system. With the USALS receiver connected to the motor, display the USALS setup menu and enter your latitude and longitude (again, you can look these up) and the software calculates the motor position for every satellite you have setup in the receiver. Select your search satellite (say, Hot Bird) and the receiver will automatically move the motor to point at the selected satellite.

How to point the motor to SouthConnect up the LNB. This loops

through’ the motor so one short cable connects the LNB to the LNB socket of the motor and a long cable connects the Rec socket on the motor to the receiver inside (this can be the original fixed dish cable, if suitable).

With a good signal meter or the receiver displaying the signal level and quality tuned to an operating

Motor position = sat position longitude

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glossaryDiSEqCDigital Satellite Equipment Control. Digital codes modulated onto the LNB power supply from a receiver to control antenna equipment such as switches and motors.

USALSUniversal Satellite Automatic Location System. Software to calculate the motor position required to aim a dish at any satellite according to its known orbital position and the latitude and longitude of the dish.

transponder on the search satellite, rotate the whole motor on the mount pole to the east and west to find the signal. When you’ve checked it’s the right satellite and have homed in on the best position, lock off the mount pole U-bolts tightly.

How to locate all the other satellites

With a USALS system the other satellites should now also be located and ready to scan for channels. With a standard DiSEqC 1.2 system you need to locate each one manually – move the dish east or west in short jumps until you locate a signal and then use tiny increments to find the hot spot and save the position.

You should also set the east and west limits for the motor – both mechanical stops on the motor and electronic limits where available – to prevent the dish hitting the wall or other obstacles if driven to the extremes.

If, in time, all the satellite positions drift off because of constant to and fro

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movement of the motor you can realign all of them at once with one command from the receiver (usually called Re-sync or Recalculate).

Most DiSEqC motors can store at least 32 satellite positions so you should have plenty of new channels to scan, to store and, finally, to watch n Geoff Bains

Motor angles: The two types of DiSEqC motor have equivalent angles to set, to follow the satellite arc

The fixed dish’s pole clamp (previously its azimuth adjustment) must be centred on the motor spindle so the dish points in the same direction as the motor

Rotate the dish on the motorised pole to align index mark with centre of U-bolt clamp bar

Tighten U-bolt nuts evenly to maintain clamp bar central

Motor spindle offset angle (usually 30° or 45°)

Motorised axis

Latitude

Dish sightline

Motor azimuth adjustment

Dish elevation setting (for declination)

Motor inclination setting (for Latitude)

Motor spindle offset angle (usually 30° or 45°)

Motorised axis

LatitudeMotor azimuth adjustment

Motor inclination setting (for Latitude)

Dish elevation setting (for declination)

Dish sightline

South