Reverse Engineering WSPR on VHF Frequency Band

Amateur radio communication used widely for experimental activities or for backup when the main communication access network fail. One of the amateur radio communications is run by using the Weak Signal Propagation Reporter or WSPR system. This system is very reliable to send messages, that composed of callsign, grid locator, and powerTx on very narrow channel widths (6 Hz) and run in the very low signal-to-noise ratio (-28 dB). WSPR systems generally work on the High Frequency band such as the 80 m, 60 m, or 40 m band, and able to reach a very long distance, up to hundreds or even thousands of kilometers. In this paper, we will propose a study of the WSPR system utility on several frequency candidates in the Very High Frequency band (2m band). The system is realized by utilizing a handy talky radio with built-in antenna and raspberry pi device as a WSPR signaling processor. The system performance is analyzed at a low signal- to-noise ratio of -14.92 dB, and still success to transmit the data. In this case we sent a soil moisture data from environmental parameter for agricultural purposes and is inserted at the powerTx.