Suherman, S., Hanafiah Rambe, A., & Widodo Tanjung, A. (2018). Underground Radio Propagation on Frequency Band 97 Mhz – 130 Mhz. International Journal of Engineering & Technology, 7(3.2), 722-726. https://doi.org/10.14419/ijet.v7i3.2.15352