Sunday, February 16, 2014

Improving Digital Television and Radio Reception

Guidelines for Improving Digital Television and Radio Reception

1.4 Television aerials
Aerial quality is a key factor in achieving and maintaining good, interference-free reception. The recommended type of aerial is one that meets a recognised standard of quality and performance, such as the CAI Aerial Benchmark (see Annex B).

The measured signal strength at the termination of the down lead should be 45 to 65 dB�V for DTT (and 60 to 80 dB�V for analogue), measured with a suitable DTT meter for DTT signals. To allow for variations in signal strength and to ensure optimum results, the signal strength for both analogue and DTT should be 6 dB above the minimum recommended level.

Consistent results cannot be expected if the minimum signal level falls below 45 dB�V on DTT multiplexes (i.e. a group of services transmitted to a single channel). However, care must be taken to ensure that the analogue levels do not exceed 80 dB�V, or the DTT receiver may display 'lock-up' or picture failure. Excessive signals may require the use of an attenuator.
The existing aerial may not be suitable for the group of DTT channels intended for reception. Specific channel-group aerials should be used, except where diverse channels are used to cover all the available multiplexes.

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