Aligning a dish with a 15-degree horizon obstruction
Satellite alignment is straightforward only when the dish has a clear view of the target. A parapet, neighbouring roof, water tank, balcony or tree can block the lowest part of the sky. A 15-degree horizon obstruction means something rises to 15 degrees above the horizontal when seen from the proposed dish position. The obstruction’s azimuth matters as much as its height, because it matters only along the bearing to the satellite.
SatPointer provides the location-based calculations needed for this task. The free web application, operated by TotalSat Limited, combines Google Maps, satellite orbital data and a selected installation point to calculate dish pointing directions for reception, uplink, downlink and mobile links. Its satellite database includes beam coverage and estimated dish-size information. This guide explains how to use SatPointer to align a dish for a site with a 15-degree horizon obstruction while accounting for the physical site around it.
Local conditions make that physical check essential. Sydney and Melbourne terraces often have adjoining walls and tight side yards, while Perth properties may face strong afternoon sun and glare. Water tanks, solar heaters and evergreen trees can create obstacles absent from satellite imagery. Google Maps can help position the dish on the correct roof, but it cannot confirm the exact stand height, a new extension or the seasonal spread of foliage.
Australian installation also brings heat, wind, coastal corrosion and workplace safety into the job. For Foxtel or Austar reception, use the receiver’s specified offset and dish geometry rather than a generic angle. ACMA administers radio-frequency and satellite communication rules under the Telecommunications Act 1997 and related instruments. Receive-only dishes do not usually need a spectrum licence, but strata or tenancy approval, safe rooftop access and licensed electrical work may still be required.
What the 15-degree obstruction means
SatPointer’s answer should be read as a satellite’s elevation and azimuth from the selected point. If the satellite elevation is 27 degrees, for example, a 15-degree roofline leaves 12 degrees of vertical clearance. If the satellite is at 14 degrees, the roofline blocks it. If it is exactly 15 degrees, reception or transmission is marginal rather than safely clear.
Do not add 15 degrees to the satellite elevation. The dish still points at the calculated elevation; the obstruction simply excludes satellites below that angle in the relevant direction. A 2–5 degree practical margin can help with foliage movement, mounting tolerance and the offset of an offset-fed dish. The free SatPointer website is the starting point for the location, satellite and pointing data.
Check whether the obstruction occupies one narrow bearing or a wide sector. A pole at 100 degrees does not hide a satellite at 130 degrees, while a long parapet may. Beam coverage is also not the same as local line of sight: a satellite can cover the city yet remain hidden by the roof.
Prepare the location and obstruction
Enter the address in SatPointer, select the correct map position and, where possible, place the pin at the proposed dish location rather than at the street address. Record the roof or ground level and the height of the dish above it. A position error shifts the calculated bearing and can matter when an obstruction is close to the line of sight.
Measure or estimate the obstruction’s elevation from the actual dish position, not from the footpath. Use an inclinometer, a phone level or a surveyed angle, and note its compass bearing. Check aerial photographs and recent site photos for poles, chimneys, tanks and trees. A 15-degree figure based on the roof edge may be wrong once the dish stands on a tripod or wall bracket.
Confirm whether SatPointer reports true or magnetic azimuth and compare it with the compass being used. Australian magnetic declination varies materially: Sydney and Melbourne readings can differ from true north by roughly 12 degrees, while Perth is near zero. Recalibrate a phone compass away from metal and use a current declination source. The PowerProNet installation notes provide a useful companion for basic setup checks.
Calculate and set the pointing angles
Choose the intended satellite and operating mode, then write down the azimuth, elevation and any reported dish offset. Reopen the result at the exact installation point and check that the target lies above the local obstruction in the same bearing. For reception, the receiver’s signal meter can confirm the final aim; uplink and downlink alignment generally demands tighter tolerance and should follow the equipment procedure.
On the mount, set elevation with a reliable inclinometer and rotate the dish to the calculated azimuth. Do not rely solely on the phone’s digital compass if its reading differs from true azimuth. On an offset-fed dish, set the physical bracket, skew and feed-arm position specified by the manufacturer; SatPointer’s satellite elevation is not automatically a substitute for the bracket’s scale.
A second person can watch a receiver meter while the installer makes small bracket adjustments. Move in short increments and allow the meter to settle. For an illustration of the same location-to-orbital-pointing method, SatPointer’s Türksat alignment guide shows how azimuth and elevation are applied to a different satellite.
Handle mounting, access and weather risks
If the only suitable satellite is below 15 degrees, the practical options are to select a higher-elevation satellite, move the dish to another position or use a suitable mast that changes the sightline. Raising the dish can reduce the apparent angle to a nearby obstruction, but only if the mount and roof structure can safely carry it. A different sector of roof may be better than forcing a clear alignment.
Choose a mount rated for Australian wind and weather, allow drainage around fixings, and secure the cable so it cannot chafe or carry water into the receiver. Coastal salt, inland heat and strong UV affect brackets and seals. Trees need ongoing checks because a clear winter sightline can disappear after growth or rain.
Do not work on a ladder in wet or windy conditions, and keep clear of overhead power lines. Roof access in strata buildings may require approval or an approved contractor. An active uplink dish can create RF exposure hazards, so follow the manufacturer’s procedure and keep people out of the beam during transmit tests.
Compare practical alignment methods
The right method depends on whether the job is a simple receive installation, a mast-mounted system or a transmit-capable terminal. SatPointer removes the orbital guesswork, but each checking method has a different balance of cost, speed and accuracy.
| Approach | Best suited to | Main advantage | Main limitation |
|---|---|---|---|
| SatPointer with compass and inclinometer | Simple receive-only installations | Inexpensive, portable and quick to set up | Depends on compass accuracy and careful bracket adjustment |
| SatPointer with receiver or signal meter | Confirming a reception path | Shows real carrier quality during adjustment | Requires some signal before precise tuning |
| SatPointer with spectrum analyser | Marginal or professional reception | Distinguishes the wanted carrier from interference | Specialist equipment and interpretation |
| Professional installer using SatPointer coordinates | Difficult roofs, masts and uplink systems | Safer access and precise mechanical alignment | Higher cost and scheduling requirements |
For this 15-degree obstruction, begin with the SatPointer calculation to rule out blocked satellites. Use a receiver meter to prove reception and fine-tune the aim. A professional installer is sensible where access is hazardous, the mast is complex or accurate uplink alignment is required.
Signal bars alone are a weak final reference because they can remain unchanged over a wide range of alignment. A recognised carrier, quality reading or spectrum meter gives better evidence, especially for marginal paths near the obstruction.
Practical recommendations for a reliable installation
Use a repeatable sequence that checks geometry before committing to a mount or climbing onto the roof.
- Enter the exact installation coordinate and confirm that the map pin sits at the dish rather than the property centre.
- Measure the obstruction from the final dish height, including its bearing and seasonal changes.
- Select a satellite above the obstruction with a practical elevation margin.
- Match azimuth to true north and set the correct offset, skew and bracket angle.
- Confirm the received carrier, then weatherproof and secure cables, fixings and entry points.
- Use a qualified installer for complex roofs, mains work or live uplink transmission.
Start at the SatPointer support contact page if a site-specific question remains, then open the calculator with the exact address and intended satellite ready. Work through the elevation check, confirm the bearing on site and make the first adjustment from the ground before carrying tools to the roof.