John Dallman definitely has the right of it, but I wanted to chime in with a small bit of additional information--the. The early warning system that the russians used, the Duga Radar (oreventually known as the "Russian Woodpecker" as it came to be called), had an enormous range of operating frequencies. It would randomly hop between different channels, sometimes interrupting legitimate broadcasts, assumably topresumably in an attempt to subvert jamming attempts and avoid crowded signal bands. This is why it got the name "woodpecker"--people's"woodpecker"; people's radios would randomly start emitting a sharp "tap tap tap" noise.
As John answered, jamming the enemy's system is effectively a declaration of attack, and would have caused an all-out attack on both sides. But in addition to that, jamming the Duga network would have likely required jamming every single radio station, including the ones the allies were attempting to use.