($) - Sensor section..... Wide-spectrum sensor starting from 150 khz up to approximately 3 Ghz . The source of the idea is the link below.
https://techlib.com/electronics/allband.htm
($$) - Relay section (synchronization, amplification, and signal cleaning)... to detect very low frequencies. Designed by Engineer John, link to the source page.
https://www.qsl.net/kd2bd/vor.html
