A study into whether a new police radio mast at Holyhead on Anglesey is affecting the television signals of people living nearby has been launched.
Tetra masts have proved controversial across the UK
People have complained their TV pictures become fuzzy and blurred when the Tetra mast on the local police station was turned on last December.
The company which put up the mast, 02 Airwave, said it was "fully compliant" with regulations.
North Wales Police Authority is carrying out the research.
Tom O'Donnell the finance and resources director from North Wales Police, said the study would establish whether the mast operators were in breach of their lease.
"This is a completely independent study and the consultants will interview the people affected as well as looking at the technical aspects.
"The aim is to determine once and for all whether this mast is the cause of this annoying interference."
A spokesman for O2 Airwave said: "[The mast] is fully compliant with the Wireless Telegraphy Act and that has been confirmed by independent reports we commissioned by engineers."
The problem can be solved by a special filter or by switching to satellite or digital TV services.
Residents said that both of these solutions were unpopular because of the cost.
A spokesperson for the watchdog body Ofcom said the problem had probably occurred because viewers have had amplifiers fitted to their television installations in order to boost the signal.
"The interference can almost always be resolved by the fitting of an appropriate filter," added the spokesperson.
" Airwave is transmitting in accordance with its licence and is under no obligation to fund the remedy."
The spokesperson also pointed out that no-one had a legal right to good television reception.
Tetra (Terrestrial Trunked Radio) is a digital mobile radio system which has been chosen by the Home Office for a new communications system for emergency services, including the police.
The system has proved controversial across the UK because of health concerns.