HF and VHF/UHF Transverter System for Disaster Area Communication

Abstract

In the natural disaster areas, a cellular-based telecommunication system is often disrupted. Handy-Talky is a power full as an ad-hoc telecommunication system for this condition. This equipment works in the Very High Frequency (VHF) and Ultra High Frequency (UHF). The VHF band is strongly influenced by the environment where is this system implemented. This system is suitable for short-range terrestrial communication. However, to develop a very long-range communication, it needs an HF type of communication system. In this study, a transverter system was built to convert the frequency signal from VHF to HF and vice versa. The transverter system was implemented on Raspberry Pi and supported by the C programming language. Two identified processes were the transverter process of converting HF signal to VHF/UHF signal and the transverter process of converting VHF/UHF signal to HF signal. The HF gateway device was controlled by VOX mode in order for it to transmit immediately when receiving voice signal from VHF/UHF gateway. The communications between these two devices with different frequency run in half-duplex mode. The voice activity detection technique was employed to replace the user, automatically activated the HT push-to-talk radio power for the threshold value of 60 dB in SNR. The calibration was conducted on EEPIS campus. The HF transceivers were positioned in D3 building and Post-Graduate building, EEPIS. It has shown that the communication process using the transverter was successful.