Azimuth correction for a dish on a metal pole
A dish on a metal pole is a common Australian installation where a rooftop location is awkward. It suits homes and farms where buildings, eucalyptus trees or neighbouring roofs block the relevant satellite view. Metro users may have NBN, but regional premises can still rely on satellite reception, the VAST regional television service or mobile satellite links.
SatPointer calculates a pointing direction from the installation coordinates, the selected satellite and orbital data. Its azimuth is a horizontal bearing referenced to true north, while elevation shows how far above the horizon the antenna must look. That distinction matters because a magnetic compass beside steel does not show true north reliably, and a leaning pole can make the bracket scale disagree with the antenna’s actual boresight.
The correction should be established before loosening the mount: convert the target to a common reference, mark true north at the pole, check the pole and bracket geometry, then make one measured adjustment. Final verification comes from the receiver’s signal-quality readings rather than from the compass alone.
Separate magnetic north from true north
First identify what your compass is showing. Most handheld and phone compasses use magnetic north, which differs from true north by magnetic declination. The offset varies across Australia: Sydney, Melbourne and Brisbane are in an easterly-declination area, while Perth can be close to zero or westerly depending on the date. Use the current declination for the installation site and year rather than a national fixed value.
Keep one convention throughout the calculation. Let T be the true azimuth from SatPointer, D be signed magnetic declination with east positive, and M the magnetic bearing needed on a conventional compass. The relationship is T = M + D, so M = T - D. For example, a true target of 214 degrees with an illustrative 13-degree easterly declination calls for a magnetic bearing of 201 degrees. Replace the illustrative value with the current local figure.
Establish a trustworthy pole reference
A steel pole and nearby galvanised fencing can distort a compass field, especially when the sensor is held close to the bracket. Test the compass several metres away and compare readings from several positions. After converting to true north, use pegs and string to lay a north-south line on the ground; keep the phone or compass away from metal while transferring that direction to the pole.
Use that ground line as the installation’s north datum rather than a reading at the bracket. Mark it clearly, check it from both ends, and keep it undisturbed while adjusting the mount. The broader receiver setup is covered in this dish alignment guide, which provides a useful foundation before adding pole-specific geometry.
Calculate the target azimuth with SatPointer
Enter the dish’s actual coordinates, ideally from a phone or GPS positioned beside the pole, not the centre of the suburb or a postcode area. A small location error can matter when the wanted satellite has a low elevation angle. The same rule applies in dense cities such as Sydney, Melbourne, Brisbane and Perth, where a nearby building can make the true horizon higher than the map suggests.
Choose the intended service rather than assuming that every signal uses the same spacecraft. The SatPointer network information can help identify satellite and network options, while the application calculates separate pointing information for reception, uplink, downlink and mobile links. Record the displayed azimuth and elevation before moving the dish. Treat the azimuth as the true bearing to the antenna boresight, not automatically as the visual direction of the reflector face.
Account for lean, roll and offset geometry
A vertical pole is the reference frame assumed by most azimuth calculations. Check it with a plumb line or inclinometer after tightening the bracket bolts. Lean has no universal correction: its effect depends on the lean direction, dish elevation and any roll in the mount. Straightening or shimming the pole is normally more reliable than trying to compensate with an arbitrary offset.
The bracket also needs a known zero. Rotate the mount to a simple orientation, mark where its index or clamp points, and compare that mark with the true-north line. Check that the yoke rotates evenly and that a bubble level remains centred. An offset-feed reflector face is deliberately offset from the electrical boresight, so follow the antenna axis used in the pointing calculation instead of visually aiming the centre of the dish.
Once the pole is plumb, calculate the remaining movement from the current orientation. If the bracket’s current bearing is B on a magnetic compass and D is signed declination, its current true bearing is B + D. The required correction is C = T - (B + D), where positive means clockwise. Using T = 214 degrees, B = 198 degrees and D = 13 degrees gives a 3-degree clockwise correction. Omit the declination term if the mount is already indexed to true north.
Apply the correction and fine-tune reception
With the target recorded, loosen the azimuth clamp only enough to rotate the assembly. Set the mount against the true-north datum and turn it to the calculated azimuth, then tighten and recheck the bubble level and pole plumb. Do not force a bent pole into alignment; reinforce or replace it, because the movement will otherwise return as wind and temperature change the installation.
When recording several bearings on a site sketch, a labelled grid helps prevent north and east being confused. The layout in this six by four grid is a useful visual model for that bookkeeping: add the target ray, pole axis, lean direction and bracket zero before turning any bolts.
Make the final change in small increments while watching the receiver’s lock indicator and signal-quality scale. Dish diameter matters here; Australian installers commonly quote 80 cm or 110 cm H-size dishes, and those apertures have different beam widths. A movement that seems trivial on a smaller dish can be significant on a larger one, while a narrow beam can make the optimum position harder to find.
Confirm the alignment and maintain it
A correct calculated bearing should produce reliable reception, but only the receiver confirms that the antenna is aimed and focused correctly. Check for a stable lock, good signal quality and normal picture or data performance. If the signal is weak, verify that the feed arm is secure and that an obstruction has not entered the elevation path before altering the azimuth.
Record the final azimuth and elevation, the date, dish size, bracket offset, pole inclination and source of magnetic declination. Coastal salt, strong ultraviolet light and summer heat can loosen fittings or damage cables around Australian backyards. Northern installations may also need cyclone-rated anchors, and vegetation can grow into the beam after months or years.
Do not improvise mains earth bonding or extend mains wiring near the dish and coaxial cable. In Australia, that work belongs with a licensed electrician, and a properly bonded metal pole is important where lightning exposure is high. These site checks protect the installation without changing the calculated bearing.
The pointing references have distinct roles:
| Pointing reference | Best use | Main limitation | Practical role |
|---|---|---|---|
| Magnetic compass | Establishes a magnetic bearing | Steel can distort the reading, and declination must be applied | Move away from the pole, convert to true north and mark a ground datum |
| Phone or GNSS compass | Provides a quick direction check | Some models show magnetic north; calibration and local metal can affect it | Confirm a bearing before transferring it to the installation |
| SatPointer | Calculates target true azimuth and elevation | Depends on the exact location and a properly referenced, vertical mount | Select the correct satellite and link, then set the bracket from the calculated value |
| Receiver signal meter | Confirms usable reception | Provides no direct angle and varies by receiver | Make small adjustments and verify lock and signal quality |
Open SatPointer, enter the coordinates of the actual pole, choose the correct satellite and link type, and record the true azimuth before adjusting the mount. Set the dish from the true-north ground reference, then confirm stable lock and signal quality with the receiver.
Save the final azimuth, elevation, dish size, pole inclination and bracket offset with the installation notes. That record lets the next technician reproduce the alignment instead of guessing around the steel.