The following are some factors that cause interference:
TELSTRA COVERAGE DISCLAIMER
All mobile devices have been tested to operate within the coverage contours of the displayed coverage maps. Mobile device coverage depends on where you are, the device you are using and whether it has an external antenna attached.
Customers should be aware that the Telstra mobile coverage maps displayed have been created using tools that predict the likely areas of coverage. Not every particular location within the identified coverage areas has been individually tested for coverage. This means that while the footprint of coverage outlined on the maps is generally accurate, there will be specific areas described as being within a coverage area where a customer's device will not work. This is a common characteristic of wireless systems. For example, coverage could be degraded or not existent in specific locations due to certain physical structures or geographic features or as a result of the device used. Physical structures which may block or inhibit coverage could include basements, lifts, underground car parks, concrete buildings, tunnels and road cuttings. Geographic features which may block or inhibit coverage could include formations such as hills and mountains or even trees.
Customers should also be aware the Telstra mobile coverage maps also may indicate planned coverage expansions of the Telstra mobile network. Coverage planned for the future is based on Telstra's rollout schedule. Telstra reserves the right to modify this schedule without notice, as required from time to time.
Data speeds experienced on Telstra's mobile networks may be affected by network availability, the type and configuration of customer equipment, the performance of external networks (for example the Internet), the signal strength of the device used and other factors such as the type of application.
The offshore coverage shown is only indicative of where a Next G® device may operate. Factors beyond Telstra's control such as the weather, tides, sea conditions and the customer's installation (type and height of antenna above sea level) can significantly influence the actual user experience of coverage, data speed and performance. Public mobile networks must not be relied upon as a primary method of emergency communication at sea.
OUT TO SEA COVERAGE
Telstra's 850MHz Next G network can typically extend 20 to 70 km out to sea from mobile base stations located near the coast. However, there are many factors like the weather, tides, sea conditions and your antenna installation (type and height above sea level) can significantly influence coverage, data speed and performance. As a result, you must not rely on the Telstra Mobile Network as a primary method of communication at sea.
To assist your mobile services when out to sea, you should use a directly connected external antenna – one that is omni-directional or a specialist marine antenna capable of 'tracking' to the best serving base station. The antenna should be mounted as high as possible on your vessel using marine grade cabling and connections.
In order for a service out to sea to work effectively, line of sight to the terrestrial base station is required. This is influenced by the height of the serving base station, land based obstructions such as trees and buildings, as well as the general topography of the land, which can block signals. Coverage will not be reliable over the horizon from a mobile base station even though it may be usable at times.