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.
