This paper presents the results of our experiment with virtual relay channels for FM Narrowband voice communications. This work was performed in both the VHF frequencies and the UHF frequencies. The following military radios were used: RT-1439a, AN/PRC-152a, and AN/PRC-117G radios. The following software defined radios were used during testing Ettus USRP b205mini connected to a desktop computer system capable of handling the processing rates for 5 Million samples per second (Msps) relay channels. This enabled receive frequencies to be placed up to 2.5 MHz apart from one another. The transmit frequencies were also placed within 2.5 MHz apart from one another due to the maximum sample rate of 5 Msps. The following waveforms were tested VHF/UHF Line of sight in plaintext and VULOS in ciphertext mode with the Tactical Secure Voice Cryptographic Interoperability Specification (TSVCIS).
