Satellite dish alignment calculator

The three settings

Azimuth is the direction to point the dish, measured clockwise from true north. A compass points to magnetic north, so use the compass bearing, which corrects for magnetic declination at your location. In the UK that's currently within a couple of degrees of true, but in North America it can be 10° or more. Keep the compass away from the dish and its metal bracket when you take the reading.

Elevation is how far above the horizon to tilt the dish. Most dishes are offset designs, where the dish face points about 20° to 25° lower than the signal it receives, so set the elevation with the scale on the dish's mounting bracket rather than by measuring the face. From the south of England, Astra 28.2°E is about 25° above the horizon. The further north you are, the lower the satellite.

LNB skew is how far to rotate the LNB in its holder, so its polarisation lines up with the satellite's. The angle is shown with the direction to turn it, viewed from behind the dish looking towards the satellite. Some satellites, including Astra 2 at 28.2°E, which carries UK services, tilt their own polarisation to suit their main service area, so the best skew can differ from the calculated one. Fine-tune by rotating a few degrees either way for the best signal quality reading.

Finding the satellite

Set the elevation, point roughly at the azimuth, then sweep slowly from side to side, a degree or two at a time, while watching the signal quality on your receiver or a satellite finder meter. Most satellites are close together along the arc, so check you've found the right one: the receiver will only lock to its channels if it has. Once you have a signal, peak it in small steps of azimuth, then elevation, then skew.

Clear line of sight

The signal needs a clear path, and wet leaves block it surprisingly well. The clearance figure shows how tall an obstacle can be, above the height of the dish, at the distance you enter in the dish's direction. A tree 10 m away in the line of sight from a dish pointing up at 25° must be less than about 4.7 m taller than the dish.

Geostationary orbit

TV satellites orbit 35,786 km above the equator, taking exactly one day to go round, so they stay in the same place in the sky. That's why a dish can be fixed. Because they're all above the equator, they appear along an arc across the southern sky from the northern hemisphere, and across the northern sky from the southern hemisphere. Radio amateurs use the same orbit: the QO-100 calculator points a dish at the first geostationary amateur satellite.

Questions