TETRA and Television Reception

What is TETRA?

TETRA is the new digital mobile radio service for use by the emergency services, including An Garda Síochána, which is currently being installed nationwide. This new service will allow communications within and between the emergency services to be more effective than present in areas where poor reception is currently experienced. The new service is also more secure as it is encrypted, which meansthat Garda radio channels cannot be monitored.

How is TETRA related to terrestrial television reception problems?

People, who live in close proximity to a Garda station or another facility where a TETRA base station is installed, may experience degraded terrestrial television reception if they have an unfiltered wideband masthead amplifier installed with their television aerial. Cable and satellite systems that are not directly connected to a terrestrial television reception system will not be affected.

Why would a masthead amplifier be installed in my television reception system?

Typically such an amplifier is used for one of three purposes:

1.         For receiving television stations that come from outside the Republic of Ireland, usually when the television user lives near the border with Northern Ireland or along the east coast.

2.         Where the user splits the television signal received so that it can be distributed to several television sets.

How does the masthead amplifier cause reception problems?

The degradation of reception experienced when a masthead amplifier is installed is caused by the masthead amplifier taking in unwanted nearby signals from outside the television band, which then overloads the amplifier causing it to perform incorrectly.

How can I solve my reception problem?

To remove this degradation of reception the television user can take one of two measures:

1. Remove the masthead amplifier. This will allow Irish television stations to be received without degradation of picture quality; however weaker signals from stations outside the Republic of Ireland will no longer be able to be received.

2. Have a suitable filter added between the aerial and the masthead amplifier. This will prevent unwanted nearby signals such as TETRA, mobile phones and private mobile radio from overloading the masthead amplifier. It should be noted that all filters placed in a television system must be physically placed before amplification and that placing a filter after a masthead amplifier will not improve television reception.

Why wasn’t a filter installed when my television reception system was initially installed?

Television reception systems have traditionally been installed in such a way that they only account for conditions that are present at the time of installation. This means that a filter would not have been installed unless a signal that could overload an amplifier was present at the time of installation.

However, now that spectrum in Ireland is becoming more densely populated as technology advances, it is good engineering practice to install filters in all new installations (and old installations that are being upgraded) where amplifiers are used to prevent future problems occurring.

Where can I get such a filter?

These filters are available from electrical suppliers who stock television aerials and related equipment. If more than one aerial is installed additional filters may be required if such additional aerials use masthead amplifiers or if a distribution amplifier is used elsewhere in the system.

How much does a filter cost?

Suitable filters can be purchased for as little as €15. However as access to a rooftop will be required to install the filter in most cases, television users are advised to obtain the services of a television aerial installer or another competent person to fit the filter for them.

If I don't want to pay for a filter is there anything else I can do?

Removing power to the masthead amplifier will in most cases resolve reception problem to Irish television stations. However the masthead amplifier itself may attenuate the received signals when unpowered causing degraded television reception. With the masthead amplifier unpowered, reception of foreign stations will most likely not be possible.

But I still want to receive stations from outside the Republic of Ireland, why should I only receive Irish stations?

It is important to note that within the Republic of Ireland no protection is afforded to television services originating from outside the Republic of Ireland such as BBC, ITV and Channel 4.

My reception was unaffected before this TETRA service was installed. Why should I have to solve this problem myself?

It is the responsibility of the end user to ensure that their television reception system is installed in such a way that it is not capable of receiving radio signals from outside the television bands. This means filters should always be installed if any sort of amplifier is to be used. This will prevent the amplifier from being overloaded by signals outside the television bands that may be present at some point in the future.