We consider the problem of deterministic broadcasting in radio networks when the nodes have limited knowledge about the topology of the network. We show that for every deterministic broadcasting protocol there exists a network, of radius 2, for which the protocol takes at least (n 1 2 ) rounds for completing the broadcast. Our argument can be extended to prove a lower bound of ((nD) 1 2 ) rounds for broadcasting in radio networks of radius D. This resolves one of the open problems posed in [28], where in the authors proved a lower bound of (n 1 4 ) rounds for broadcasting in constant diameter networks. We prove the new lower bound for a special family of radius 2 networks. Each network of this family consists of O( n) components which are connected to each other via only the source node. At the heart of the proof is a novel simulation argument, which essentially says that any arbitrarily complicated strategy of the source node can be simulated by the nodes of the networks, if the sou...