Artificial intelligence (AI) techniques, particularly autoencoders (AEs), have gained significant attention in wireless communication systems. This paper investigates using an AE to generate featureless signals with a low probability of detection and interception (LPD/LPI). Firstly, we introduce a novel loss function that adds a KL divergence term to the categorical cross entropy, enhancing the noise like characteristics of AE-generated signals while preserving block error rate (BLER). Secondly, to support long source message blocks for the AE's inputs, we replace one-hot inputs of source blocks with binary inputs pre-encoded by conventional error correction coding schemes. The AE's outputs are then decoded back to the source blocks using the same scheme. This design enables the AE to learn the coding structure, yielding superior BLER performance on coded blocks and the BLER of the source blocks is further decreased by the error correction decoder. Moreover, we also validate the AE based communication system in the over-the-air communication. Experimental results demonstrate that our proposed methods improve the featureless properties of AE signals and significantly reduce the BLER of message blocks, underscoring the promise of our AE-based approach for secure and reliable wireless communication systems.