Radio Frequency (RF) Overload and Digital Terrestrial Television (DTT)
I use a roof top aerial to get free to air TV now. What is changing?
Analogue transmission of TV ceases on 24 October 2012 and is changing to digital which is much more efficient and will have the potential for more programming and better sound and picture. Digital Terrestrial Television uses less radio spectrum to carry the programming. As a result, spectrum which up to now has been used for analogue television will be released for other purposes such as 4G future generation mobile broadband services (LTE).
What is LTE?
LTE is the new fourth generation (4G) mobile phone service which it is envisaged will be rolled out early next year, it is an improvement over the existing 3G services as it offers users faster data rates and improved mobile broadband services.
What is a Masthead amplifier?
A masthead amplifier is used to boost television signals that are received by a roof-top antenna, if there is a small plastic box mounted on the pole below your antenna it is likely to be a masthead amplifier.
Do I need an Amplifier?
SAORVIEW, which is the free digital television service received with an aerial, has been planned without factoring in the use of amplifiers so it should not be necessary to use amplifiers to receive SAORVIEW. Only in areas of weak signal or in coverage ‘black-spots’ might it be necessary to use an amplifier. In some instances amplifiers are installed where there are a number of televisions used in the house, even in these instances high-gain masthead amplifiers are not required, the use of appropriate antennas and good quality cable is all that is required in most instances.
How Does Using an Amplifier Affect My TV Reception?
Amplifiers are very prone to suffering from a problem known as Radio Frequency (RF) Overload. This is a phenomenon that commonly occurs due to the way in which amplifiers operate. When this occurs it often leads to the complete loss of television reception.
What is RF Overload?
Radio Frequency (RF) Overload is a phenomenon that usually affects amplifiers and other sensitive electronic circuits. The performance of an amplifier is adversely affected when it is used in the presence of a signal that is strong relative to the signal intended for reception; in such instances the television signal is completely degraded resulting in a loss of picture and or sound. Many of the amplifiers currently in use are more prone to RF Overload from LTE signals as they amplify signals in the LTE Bands in addition to the DTT bands.
What will be affected by RF Overload?
If you receive off air reception of the national services (RTÉ, TG4, TV3) by means of a roof top aerial which is fitted with a mast head amplifier, you may suffer degradation or even loss of television reception when LTE services come on stream from early 2013 onwards. This loss is likely to be as a result of the amplifier on your roof amplifying an unwanted signal and suffering overload.
How can I solve my reception problem?
You 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; it is very likely that the amplifier is not required for the reception of DTT signals.
2. If absolutely necessary, have a suitable filter added between the aerial and the masthead amplifier. This will prevent unwanted nearby signals, such as LTE, 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 currently available from many suppliers who stock television aerials and related equipment. ComReg has performed testing on some available filters to ensure they are suitable for the job at hand, all filters tested to date have been found to be suitable.
How much does a filter cost?
Suitable filters can be purchased for as little as €15-20. 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?
SAORVIEW reception has been planned without factoring in the use of amplifiers so it should not be necessary to use amplifiers to receive SAORVIEW. Filters are only required where an amplifier is in place. Amplifiers should only be used if absolutely necessary, so in many cases there will be no requirement for an amplifier or a filter.
My reception was unaffected before the LTE 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 it is good practice to install a filter 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 and ensure that your television reception remains unaffected.
Where can I find further information on digital television?
Other Useful Documents
RTÉNL – SAORVIEW FAQs:
RTÉNL – Connecting a Television Set to SAORVIEW: