Planning a Dish Array for Inclined Orbit Satellites with SatPointer

Inclined orbit satellites drift north and south of the equator each day, tracing a slow figure-eight across the sky. A single antenna can chase that drift with a motorised mount, but a fixed array of dishes has to be planned around the worst case in the diurnal loop. SatPointer brings that planning step into a single workspace.

The application overlays Google Maps imagery with live orbital elements, so the look angles for every satellite of interest appear in the same window as the address and the roofline. Installers working across Australia rely on this blend every week because the look angles from Perth, Cairns, and Hobart sit at very different elevations.

What makes the tool valuable for a multi-dish array is the way it lays out each inclined satellite, its predicted arc over a 24-hour cycle, and the surrounding beam contours on the same canvas. The planner can then confirm clear line of sight, size each antenna, and lay out the spacing before a single pole is planted.

Why Inclined Orbits Change the Geometry

A satellite parked on the equator sits at a constant elevation once a dish is pointed at it. An inclined bird wanders a few degrees north and south each day, and that wander grows with the age of the satellite. For a one-off home installation this drift is invisible because the antenna beam is wide enough to swallow a degree or two. For a bank of feeds pointed at the same cluster, the drift means one dish sees the satellite rising while the dish beside it sees it setting.

The effect grows the further you are from the equator. A site in Darwin already looks at a steep elevation for many birds, and the inclined orbit trace is compressed into a smaller window of sky. In Sydney or Melbourne, the lower look angle stretches the apparent path and demands that adjacent dishes be spaced apart. SatPointer exposes these geometry choices by plotting both the current and the historical extreme positions for each satellite. Planners across the Tasman face a similar pattern, and the Pacific Horizons layout notes walk through a comparable problem set.

Reading the Ephemeris Inside SatPointer

The engine behind every look-angle calculation is a set of orbital elements called TLEs. SatPointer pulls fresh TLEs from public sources and lets the user pick the moment of interest rather than relying on a single date stamp. For inclined satellites this matters because the rate of drift is not constant. The satellite speeds up as it crosses the equator twice a day and slows near its northern and southern extremes.

A useful trick is to drop the analysis time forward by a year and then back by a year to see how the orbit evolves. Some operators want to know whether a satellite will remain usable throughout the intended service life of the site. Watching the predicted arc widen or shrink over time gives a clear sense of how much margin to bake into the antenna mount. For remote mining camps in the Pilbara or the Top End, that margin can be the difference between reliable comms and a service truck rolling out for hours.

Picking the Site and Avoiding Obstructions

A dish array needs a clear sky window that stretches further north and further south than a single geostationary bird would demand. In Australian suburbs that often rules out cramped terraces in Sydney or older Melbourne streets where neighbouring rooftops crowd the horizon. A block of land on the urban fringe, a farm shed in central Victoria, or a hilltop compound near Bendigo will usually offer a better horizon. SatPointer's Google Maps overlay makes those choices visible, with a yellow line drawn from the chosen pin showing the minimum elevation for a clear line of sight.

Tree cover is the hidden enemy for many installations. A gum tree that looks harmless in summer can swallow an entire feed during a winter growth spurt, and the worst case is often an inclined satellite that drops to a few degrees elevation at its southern extreme. The tool's horizon profile lets the installer trace the silhouette of nearby trees and buildings so the dish spacing can be widened before the concrete is poured. Anyone working around Cairns or Townsville knows how quickly vegetation grows back after a cyclone.

Parameters Worth Verifying Before Pouring Concrete

Look angle envelope over a 24-hour cycle, including the highest and lowest elevation reached by the inclined satellite.
Predicted arc twelve months forward and twelve months back to size the mount tolerance.
Beam contour for each target bird, confirmed against the actual installation address rather than the city centre.
Local terrain elevation at the chosen pin, because Google Maps often quotes a street address centroid that sits below the actual roofline.
Closest neighbour structure within two dish diameters of any planned mount.
Horizon clearance for the southern and northern extremes of the inclined arc.

Beam Maps and Dish-Size Choices

A satellite beam map looks tidy on a sales brochure, but the real performance on the ground depends on the intersection between the beam contour and the actual installation address. SatPointer loads beam coverage data alongside its pointing information, so a planner can confirm that a chosen site sits inside the high-power zone of every satellite in the array. The map also reveals the contours where the gain rolls off, which is exactly where a wider dish earns its keep.

Broadcasters and ISPs serving remote customers face a different question: how many subscribers can the array actually serve before the link budget collapses? The tool's estimated dish-size field takes the local EIRP figure, the target data rate, and the available modcod to produce a starting point. An installer near Perth servicing the Wheatbelt might pick a 1.8 metre dish for the main beam and a 2.4 metre dish for the edge. Planners chasing broader coverage arcs face similar decisions, and the Amazonas alignment notes document the dish sizing that follows from a careful beam check.

Mounting, Spacing and Weather Hardening

Mounting a dish array is part alignment, part civil engineering. SatPointer gives the azimuth and elevation to within a fraction of a degree, but the installer still has to choose between a non-penetrating ballast mount, a concrete pier, or a wall bracket. Each option tolerates a different amount of vibration, and the choice often depends on the local wind zone. Sites near the coast around Geraldton or Whyalla need stiffer mounts because salt-laden gusts shake the structure more than inland sites.

Dish spacing is governed by two competing forces. The dishes have to be close enough to share a single RF chain and cabling trough, yet far enough apart that sidelobes from the neighbour do not raise the noise temperature. The rule of thumb is roughly two to three dish diameters between centres, but SatPointer makes it possible to plot the exact interference envelope for the satellites in the plan. For a typical 1.2 metre array that means around three metres centre to centre.

Weather hardening matters more in the tropics than the temperate south. A dish in Darwin has to shed monsoon rain without flooding the feed horn, while a dish in Hobart has to survive hail and southerly buster winds. Stainless hardware and waterproof cable glands are not optional in either climate.

Australian-Specific Site and Workflow Checks

ACMA licensing requirements for fixed receive-only dishes above the exempt size, plus any apparatus licence for an uplink.
Local council permits for dishes over the size threshold, with heritage overlays in parts of Adelaide and Fremantle adding an extra layer.
Bushfire Attack Level rating for any site sitting inside a designated BAL zone on the rural-urban fringe.
Cyclone region rating for installations north of roughly Rockhampton, where structural ties have to be upgraded.
Earthing and lightning protection to the relevant Australian Standard for the site and the local soil resistivity.
Pest and vermin screening for cable entries, particularly on grain-belt sites where mice and ants find warm amplifier cabinets irresistible.

The clearest path from a blank rooftop to a working array is to start with SatPointer and let the tool guide every other decision. Pick the pin, list the inclined satellites that matter, and let the pointing data settle into a layout. From there the choices around dish size, mount type, and spacing follow naturally.

For Australian operators the payoff is a site that keeps working through the slow drift of an ageing fleet, and a workspace that can be reused for the next project. The combination of Google Maps, live orbital elements, and beam coverage in one place turns planning into engineering.

Crews that handle a steady stream of site documents by email should build the habit of automating trust verification on every attachment from a contractor or vendor. Anyone who has wrestled with an inclined satellite on a fixed mount will recognise the value of seeing the whole picture before the first hole is drilled. Run the SatPointer planning tool on your next project and pin the resulting layout to the project folder before the concrete is poured.