The cheapest way to block and reflect RF radiation is to create a reflector out of aluminium mosquito net. The net is becoming more problematic to find today in store but some hardware store still have it for seal for as low as US$5 for a linear meter. I used it last week to block RF radiation from an unknown source to penetrate my kitchen via a big window. I cut the net and connected it to the bars on the windows using metal wires. The outcome was nice and RF measurements showed no RF!