Slashdot Mirror
UK Government To Offer Free TV Filters For 4G Interference
judgecorp writes "4G services could interfere with terrestrial TV in the UK, so the government plans to offer one free filter for every household affected by the issue. The analysis suggests that 2.3 million households could be affected, but many of those have cable or satellite TV, so the plan might only need a million filters (each household only gets one, even if they have many TVs)."
For a few more months in the UK analog TV will use 470-862MHz
The last few analog transmitters will soon be switched off,
the replacement digital transmitters will just use 470-790MHZ.
806-854MHz was auctioned off in 2009. 790-806MHz may be used for other tings in areas where it is not used for digital TV.
The worst case scenario for TV interference is roughly this.
Someone's house is on the edge of the coverage area of a digital TV transmitter which is on the highest multiplex frequency. They are 35miles from the transmitter and have a big TV antenna on a twenty foot pole on the chimney with a wideband preamp on the pole.
The TV signal is just barely strong enough to give a picture and only freeze occasionally when a pigeon flies in front of the antenna.
The TV signal is 8MHz wide ending at 790MHz.
A mobile internet base station push out 100 watts is installed 100 meters away from the house using frequencies starting just 16MHz higher at 806MHz.
In terms of power the mobile internet signal might be 70dB stronger, that's ten million times the received power.
The base station signal is strong enough that it overloads the masthead preamp. It dosn't even matter if the TV decoder can handle a massive signal close to a very weak signal, (and it probably can't) because the preamp is clipping and the weak TV signal is lost before it even gets to the TV.
In theory with good planning will mitigate this considerably.
In practise vast amounts of existing TV equipment is specifically designed to receive and amplify the frequencies that have been sold oof for other uses.
Mobile applications need lots of base stations close to the users.
Inevitably lots of people will have a base station on a tall building that they can see out of the window in an area where the TV transmitter is twenty miles away.