Radio communication system permits the use of a shared transmission channel by all the terminals during data transmission. MAC protocol plays an important role in regulating the allocation of transmission channels in a multi-terminal communication networks. Implementation of P-CSMA in radio communications can minimize the probability of data collisions. The first step in this research is to determine the impact of packet length on packet delay by modeling the point to point communication. The packet data frame is based on AX25 protocol. The next step is to model multi-terminal communication and implement test scenarios of data collisions between the terminals. As the results, the maximum delay of point-to-point communication with packet length of 250 bytes is 8.34 seconds and the delay of data transmission when the collision occurred have a minimum value of 5.24 seconds and a maximum value 16.34 seconds