UHF signals – ultra high frequency – TV aerial signals

UHF signals range from 470 – 854 MHZ

Channels 21 – 68, each channel is 8MHZ wide

CAI benchmarking scheme

Standard 1

The highest standard – intended to use in fringe or areas that can be difficult for reception, where improved C/N ratios are required to get better reception

Standard 2

intermediate standard – for grouped or wideband aerials where slightly better signals are avaiale

Standard 3

minimum standard – for use in high signal areas

Standard 4

Mainly Log periodic aerials, for wideband aerials that need performance better than standard 3

Analogue TV signals

drop off (threshold) signal level 47dBuV

Minimum level                                   60dBuV

Maximum level                                   80dBuV

Digital signals

Digital signal levels

Minimum signal at receiver/TV   45dBuV

recommended signal level            50dBuV

Maximum signal level                      70dBuV

Ideally 45 – 65 dBuV

Digital carrier noise level ratios - C/N ratios

reliable/good reception – 26dB or better

marginal reception -            23-25 dB

Unreliable reception           22dB

Bit error rate – BER

The lower the BER the better.

Digital receivers can normally operate perfectly Ok if the BER before error correction is equal to or better than 2E-4 ( 2 errors in every 10,000 bits of data)

A digital TV or receiver corrects errors as they come in. When there are too many errors, the picture starts to ‘pixelate’ or/and break up. With very poor BER the picture can be unwatchable.

 

Digital signal level considerations

Please note that digital signal levels transmit normally at 20DBuV lower than analogue. So you have to assess the optimum analogue signal levels (until March 2012) and marry that with the optimum signal levels for digital.

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