This paper investigates multi-hop wireless ALOHA ad hoc networks evaluating the bit error rate (BER). It is proposed an alteration of the Friis propagation model which allows its application to any node density with random network topology and obeys the law of conservation of energy. The results show that the adapted model appropriately describes the BER performance for dense networks. It was also verified that the increase of transmission power in dense networks without augment in transmission band does not improve the BER performance and it has importance to sensor networks in which energy consumption is crucial.