Offset Feed Angle Calculations for Australian Satellite Dishes
An offset dish places its feed horn to one side of the reflector’s central axis, so the direction bringing a satellite signal into the feed is not always the same as the direction printed for the dish centre. SatPointer, the free browser tool operated by TotalSat Limited, combines Google Maps, orbital data and the installation position to calculate pointing information for reception, uplink, downlink and mobile links. This is useful across Australia wherever a household, farm, vessel or community site depends on satellite reception.
The important distinction is between a fixed mechanical offset and the changing look angles. A dish’s offset-feed geometry belongs to the reflector; azimuth and elevation depend on the chosen satellite and location, while LNB skew can change for linear polarisation. SatPointer can apply the relevant geometry when the dish details are supplied, but it cannot infer a maker’s offset from the dish diameter alone.
How offset-feed geometry changes pointing
An offset reflector is a precise, tilted instrument rather than a flat panel turned directly at a target. The feed horn’s boresight is the line that must face the satellite, while the reflector axis and visual centre of the dish can point elsewhere by the specified offset angle. The correction belongs in the mechanical setup, not in the receiver’s signal-quality menu.
| Dish arrangement | Horn position | Pointing reference | Main installation risk |
|---|---|---|---|
| Offset-fed reflector | Displaced from the reflector axis | Specified feed or boresight line | Reversing the offset or applying it twice |
| Centred prime-focus reflector | Directly on the reflector axis | Central feed axis | Feed obstruction and a narrower usable sky area |
| Motorised offset reflector | Displaced on a moving mount | Calibrated feed line plus drive limits | Losing the home position or tensioning cables incorrectly |
Each construction changes what the installer aims. A centred prime-focus dish places the horn directly on axis, whereas an offset dish shifts it sideways to reduce blockage and spillover. Motorised systems add stored azimuth and elevation limits to the same geometry. Always compare readings using the same viewing direction—usually from behind the dish—and the same true-north reference.
SatPointer runs in a browser, which is useful on a laptop before a roof visit. Keep this pointing workflow separate from entertainment-app downloads: a page offering Top Follow APK may serve another purpose, but it does not establish the mechanical offset of your reflector.
Preparing the location and dish details
Begin with a precise installation pin. In a city such as Adelaide or Perth, an address-level error may not matter at geostationary elevation, but a rural site near Carnarvon or in the Bass Strait region can see a noticeable bearing change. In SatPointer, enter the actual installation location rather than relying only on the street address, and confirm that the map pin sits on the correct side of the property.
Select the satellite from the database and choose the relevant reception, uplink, downlink or mobile mode for the installation. The satellite record also provides beam-coverage information and an estimated dish-size guide. Those figures help confirm that the target is reachable and that the proposed dish is suitable before anyone starts climbing or drilling.
Collect the following information before requesting a direction:
- Dish make, model and nominal diameter, including any offset marking
- Manufacturer’s stated offset-feed or inclination value
- LNB type: circular, linear, true-zero linear or skew-feed
- Mounting details, including which side of the mast carries the dish
The first two items are essential for a model-specific result. Circular LNBs do not require a rotating feed to match a linear satellite signal, while a linear LNB may need a roll or skew setting. A side-view photograph and a note of the mast orientation can prevent a sign error later. Installers who regularly publish setup advice can also add the free SatPointer widget to a club, forum or trade page so visitors can reach the calculator quickly.
Reading SatPointer’s calculated direction
SatPointer’s principal outputs are the satellite azimuth, elevation and orbital context. Azimuth is read clockwise from true north, while elevation is measured above the horizon. For an offset installation, establish whether those figures describe the reflector boresight or the feed line. Where the dish options accept an offset value, enter the maker’s figure before requesting the final direction. The calculator then applies that geometry rather than leaving the installer to guess.
A practical account of QAF dish setup shows why a real dish model and site photograph belong beside the numbers. Generic instructions copied between installations can easily reverse the offset. It is also worth reading the dish label or manual in ordinary daylight: a moulded arrow, feed-arm position or etched angle is more reliable than a forum estimate based only on diameter.
Think of the correction as a rotation, not as extra elevation. Conceptually, SatPointer calculates the target vector and rotates it through the fixed offset angle according to the selected dish convention; the sign depends on the horn side and viewing direction. Do not add the same number to both azimuth and elevation, and do not apply it twice. If SatPointer shows a separate skew value, treat that as the changing polarisation adjustment, not as the fixed feed offset. A changing value labelled as offset should be checked against the dish manual.
Adapting the calculation for Australian conditions
Australian conditions add another layer to the calculation. Foxtel subscription television, SBS reception, regional Freeview services and remote broadband such as Sky Muster all have different carriage arrangements. A directory such as live TV listings may help identify a broadcaster or channel, but it does not prove that the service is carried on an Australian satellite beam. Confirm the platform with the local provider before moving a dish.
Use these checks when assessing an Australian installation:
- Use true north; magnetic variation differs between locations such as Alice Springs and Hobart
- Check the chosen satellite’s elevation and any local obstruction from the actual dish position
- Match the platform, transponder and conditional-access requirements to the receiver or set-top box
- Record the calculation date, dish position and mast orientation for future maintenance
Large distances make these records valuable for farms, mine sites and caravan clubs, while coastal salt, outback dust, intense ultraviolet and summer heat can change the best adjustment technique. Check brackets, seals and cable strain rather than relying on a momentary strong reading. A caravan or boat installation should also use a mobile-link calculation that includes the dish’s normal height above the water or ground, since even a small height change alters the horizon.
In western Australia, a low western horizon may make a geostationary satellite unobstructed from open country but blocked by terrain or trees near Perth’s eastern suburbs. In central Australia, heat can move a bracket after noon. Recheck the physical aim during a cool period and after the mount has settled, especially if reception changes between the afternoon and evening.
Turning the result into a reliable installation
Calculate on the ground before climbing. Note the azimuth on a fixed reference such as a wall or pole, set the approximate elevation, and then apply the offset in the direction shown by SatPointer and confirmed by the dish manual. Avoid using a phone compass beside a steel mast or roof; use the displayed true bearing, a sighting compass held away from metal, or a professional inclinometer.
Follow the same sequence at the dish:
- Set true azimuth and approximate elevation without applying the offset twice
- Rotate the complete reflector to the specified offset while watching the feed or boresight marker
- Confirm mast plumb, bracket tightness and cable routing before final fine adjustment
- Tune by receiver quality and error rate, using signal strength only as one indicator
Common failures include copying a universal 25-degree offset, confusing LNB skew with reflector offset, and accepting a picture lock based only on signal strength. Freeze or pixelation can also come from dish movement, a poor cable joint, wrong polarisation or a marginal transponder, so change one variable at a time. Where reception is marginal, compare the calculated target with the satellite’s beam coverage and estimated dish-size guidance before replacing hardware.
Use SatPointer at the planning stage, save the location and dish details, and produce a repeatable alignment record for every technician who visits the site. If the model, mounting orientation or offset specification is uncertain, send those details to SatPointer support before installation and ask for the applicable pointing convention. With the mechanical offset confirmed and the calculated direction recorded, the final adjustment becomes a controlled process rather than trial-and-error.