The body tasked with protecting the Freeview TV service from interference from 4G mobile services says "no more" than 90,000 UK households are at risk.
Following tests conducted across the country, the at800 organisation has provided the estimate, which is based on the threat from 4G services running in the 800 MHz spectrum band.
As mobile operators prepare to activate new 4G services by turning on masts, at800 is sending out postcards to households warning them of potential interference, and what can be done to address it.
A small device fitted between a house aerial and the TV can solve the problem. The devices will be provided and fitted for free if at800 is contacted by consumers about problems.
In London, in particular, said at800, Freeview received from the Crystal Palace transmitter is "unlikely to be affected by 4G mast activation" because of the strong terrestrial television signal and its relatively large frequency separation from 4G at 800 MHz.
Only new 4G services at 800 MHz could cause problems with Freeview, and existing 4G services from EE operating at 1800 MHz can not disrupt television reception.
The at800 organisation is funded by the main UK mobile operators with 800 MHz spectrum allocations to provide 4G services, following this year's Ofcom spectrum auction.
Earlier this month Vodafone said it wouldn't be launching its 4G service until the "end of the summer".