Calculate the right coax run for your LNB and receiver using SatPointer
In a country where a station homestead in the Pilbara might be 400 kilometres from the nearest town, and a fibro shack on Tasmania's east coast can sit behind a granite ridge that blocks every terrestrial tower, the satellite dish is still the most reliable way to get a picture on the telly. Picking the right LNB and locking onto the right satellite is only half the job, though. The piece of coax that runs from the feedhorn down to the set-top box decides how much of the signal actually survives the trip, and choosing the wrong length or the wrong cable type quietly turns a strong dish alignment into a pixelated mess at sundown.
Most Australian installers learn this the hard way after a few long runs across tin roofs in Darwin or up the side of a Colorbond shed in Mildura. SatPointer does the maths for you, factoring in the dish size, the LNB's local oscillator figure, the satellite's downlink frequency, and your receiver's sensitivity, so the cable run you order is the one that actually delivers a usable carrier. Below is how to put the tool to work end to end, and how to read the numbers it spits out.
Why coax length changes your signal budget
Every metre of coaxial cable between the LNB and your receiver eats a slice of signal strength, and the slice gets thicker as the frequency climbs. A typical RG6 run at 11.7 GHz, the top end of the Ku-band that Optus 10 and Intelsat Galaxy satellites use for VAST distribution, loses around 6 dB every ten metres, while the same cable at 4 GHz on C-band loses closer to 2.5 dB. Halve the run and you give the receiver back that budget, which is often the difference between a lock and a "no signal" banner on the screen.
The trick Australian installers lean on is to treat the cable run as part of the link budget rather than a passive afterthought. SatPointer lets you drop in your LNB model and your receiver's minimum input figure, then it works backwards to show the maximum cable length that keeps the carrier above the demodulator's threshold. If you cross that line, the answer isn't a bigger dish, it's a lower-loss cable or a shorter route, and the VSAT network selection guide walks through the same logic for two-way installations.
Feeding your hardware specs into SatPointer
Open the SatPointer map and drop the installation pin on the actual roofline, not just the property address. In a suburban Adelaide street the difference might be twelve metres to the dish, but on a rural block between Bendigo and Swan Hill you might have forty metres of trench or wall cavity to deal with. Pin accuracy is what makes the cable-length estimate useful.
From there, pick the satellite you're aiming at (Optus D2 for VAST, Intelsat 19 for some Pacific beams, Galaxy 28 if you're chasing US content on the east coast), choose the dish diameter from the dropdown, and select the LNB. SatPointer stores the local oscillator and noise figure for most common LNBs, so the tool can estimate a usable carrier-to-noise margin at the receiver end once a cable type and length are entered. If your LNB isn't in the list, the noise figure and LO frequency can be typed in by hand.
Measuring the practical run from dish to receiver
The straight-line distance on SatPointer's ruler is a starting point, never the final figure. A cable routed down a brick wall, through a ceiling cavity, and across a hallway in a Queenslander home will be at least fifteen percent longer than the geometric distance. Add another metre for a service loop behind the dish so the LNB can be swapped without re-terminating, plus another half metre for the drip loop where the cable enters the building.
For Australian homes this matters more than in denser overseas housing because the receiver is often a long way from the dish. A miner in Newman running Foxtel to the donga, a grazier near Cobar with a VAST box in the shearer's quarters 80 metres from the homestead dish, or a grey nomad parked at a Big4 in Cairns, every one of these situations needs the real cable length, not the optimistic one. SatPointer's Intelsat Galaxy pointing reference shows the elevation, azimuth and polarisation figures you'll need to capture before you pull the cable.
Picking the cable and connectors that suit the run
Once SatPointer tells you the longest run the link budget will tolerate, the cable selection is straightforward. The shorter the run and the lower the frequency, the thinner the cable you can get away with. Push past about 25 metres on Ku-band and you'll be looking at LMR400 or proper RG11 with a solid copper core rather than the cheap CCA RG6 sold at the big-box hardware shops.
Match the row in the table below to the maximum length SatPointer gave you, then add a safety margin of around 10 percent for ageing and connector losses. Two quality F-connectors at each end will eat another 0.5 dB, and a cheap crimp can blow that out to 2 dB without you noticing.
| Cable type | Loss at 11.7 GHz (dB/10 m) | Loss at 4 GHz (dB/10 m) | Best suited run (Ku-band) | Notes |
|---|---|---|---|---|
| RG6 (CCS core) | 6.2 | 2.7 | Under 10 m | Cheap, fine for short urban installs |
| RG6 (solid copper) | 5.6 | 2.4 | 10–15 m | Better for most VAST home installs |
| RG11 | 3.4 | 1.6 | 15–30 m | Heavier, harder to bend around tight eaves |
| LMR400 equivalent | 2.5 | 1.1 | 25–60 m | Outdoor-rated jacket, ideal for farm and station runs |
| LMR600 equivalent | 1.6 | 0.7 | Over 60 m | Long-haul backhaul, professional-grade |
For multi-dwelling setups, such as a motel in Broome running a single C-band dish to a dozen rooms, SatPointer's beam coverage map also helps decide whether a single LNB and a multiswitch will cover the block, or whether each room needs its own shorter cable and a separate LNB. The numbers always come back to the same constraint: keep the cable run as short as the building will allow, then pick the cable type that makes the residual loss invisible to the receiver.
Get the cable length right on your next Australian install
Cable that lives happily on a rooftop in Hobart will be punished by a January afternoon in Carnarvon, where the mercury sits in the mid-forties and the UV is ferocious. SatPointer's length figure assumes a clean, undamaged cable, so the Australian installer has to build in headroom for the local conditions, and the two checklists below help turn the calculated number into a working install.
Field checks and adjustments for the calculated length
Practical signs the run is too long or the wrong cable:
- Picture breaks into blocks during the afternoon when the LNB heats up
- Signal quality drops further after a storm than it did on a dry day
- The cable feels soft or the jacket shows cracks after one summer
- The receiver reports a lower Eb/No than SatPointer predicted by more than 2 dB
- Foxing or green verdigris appears on the connectors within a year
Things to do before accepting the calculation:
- Use a UV-rated, flooded-core or gel-filled cable for any run exposed to direct sun
- Specify compression F-connectors rather than twist-on types, especially near the coast where salt air corrodes copper quickly
- Run the cable through UV-stable conduit or behind solar shielding on tin roofs
- Earth the shield at one end only, following Australian Standard AS/NZS 1768 for lightning protection on antenna systems
- Allow at least one extra metre at the dish for a proper drip loop so rainwater doesn't track into the wall cavity
Try SatPointer with your own LNB, receiver and satellite choice and see the maximum cable length the tool gives you for your roofline, then drop the result straight into your install quote. The free web app works from any browser, and a customisable widget can be embedded on a tradie's website so customers can plug in their own address and watch the cable-length estimate update as the dish moves around the property. For anyone whose livelihood depends on a clean signal, from a solo technician in Ballarat to a fly-in fly-out comms crew servicing a mine camp near Tom Price, that kind of instant feedback turns a guess into a guarantee before a single drum of cable is unrolled.