
1) Block signals
Found on
https://www.crosswordclues.com/clue/jamradio

JamRadio (formerly Jam 1575) is Hull University Union`s student campus radio station. As of 2012, the station broadcasts twelve hours per day throughout the year. It was originally broadcast on 1575 medium wave (MW), but now airs solely on the Internet. The station is overseen by a subcommittee of Hull University Union`s Media and Marketing Comm.....
Found on
http://en.wikipedia.org/wiki/JamRadio
No exact match found.