I assume that you’re referring to a satellite dish, which unless it’s one of those privately installed monstrosities that provides access to international transmissions, likely belongs to Foxtel, Telstra, or Optus.
In that case it’s usual for those companies (3) to initially obtain an Installation Agreement for the property signed by the Secretary of the Executive Committee (E/C) or the Plan’s Strata Manager, which subject to the conditions of that document, permits the company to then place their equipment including satellite dishes, cabling, and conduit on the Common Property on an on-going basis.
All equipment installed by the three (3) major providers remains theirs, and as that includes the satellite dish there’s no issues with the Owners Corporation (O/C) becoming responsible for any maintenance or repairs, and in fact these companies will remove their satellite dishes if requested to do so by an O/C.
If you’re still concerned about the installation OR if it’s indeed one of those designed for international reception, the installer may have made contact with the E/C or Strata Manager prior to the installation if that’s necessary to access the property, so you could in the first instance contact either of those to ascertain if any Installation Agreement exists and/or if contact was recently made, and to which Unit it related.
If all of the above draws a blank and you or your E/C still have legitimate concerns, the Strata Manager could be instructed to letterbox-drop all residents requesting those receiving satellite television programs to contact them within a reasonable timeframe to enable records to be updated (or some for other plausible reason), together with an advice that any unreported satellite dishes will be removed from the common property by the O/C.
Whether removal is actually implemented would depend upon the response, but that’s a little extreme unless justified by the nature of the installation (e.g. shoddy or unsightly).