Masthead & distribution amplifiers FAQ
What are masthead and distribution amplifiers?
Masthead and distribution amplifiers are used in television systems to increase the level of the signal received at a television set. Television masthead and distribution amplifiers can produce radio signal interference. Incorrect use or faulty amplifiers can affect broadcast television reception, mobile phone systems, and two-way radio communications systems.
How do they cause radio signal interference?
There are three causes of interference. These are:
- overload (high-level signals cause the amplifier to distort)
- mixing (multiple radio signal sources combine within the masthead amplifier)
- oscillation (a result of signal feedback through aging, damaged or faulty installation).
Who is responsible for any interference?
The person who owns or operates a masthead amplifier or distribution amplifier is responsible for any interfering signals radiated by the amplifier. An owner may not be aware that their television system includes an amplifier.
The ACMA is responsible for investigating radio signal interference where it is suspected that a provision of the Radiocommunications Act 1992 is being breached. For instances of radio signal interference where the Act is not being breached, it is appropriate for a reputable Aerial installer or technician to resolve the matter.
When the source of the interference has been identified as a faulty masthead amplifier or distribution amplifier, the owner or operator of the masthead amplifier will be required to arrange for the amplifier to be repaired or replaced.
How do I know if I have a masthead amplifier connected?
A masthead amplifier can usually be seen as a small grey or black plastic box attached to the pole supporting the television Aerial. There will be wires running from the Aerial into the box and a lead running down into the house to the television set. There are other devices that look similar to masthead amplifiers. The amplifier may also be out of sight in a roof cavity.
Amplifiers usually draw power through the Aerial cable from a 240-volt plug pack, which is usually found near or behind the television set. The plug pack is wired to a device known as a power injector attached to the Aerial cable going to the Aerials.
If you have such a device, then it is almost certain that it is a masthead amplifier.
How do I know if I have a distribution amplifier connected?
Distribution amplifiers are generally used where many television outlets are available on the premises. They may be located in the roof cavity or within service ducts or cupboards. Distribution amplifiers are usually physically larger than masthead amplifiers and require a 240-volt power supply to function.
How can interference problems be corrected?
Cabling and amplifier faults are responsible for a large number of the problems caused by masthead and distribution amplifiers. Care needs to be taken with the installation and maintenance of the cabling for the Aerial and amplifier.
The following instructions are for use by people operating and installing the amplifiers.