VLF Beacon Receiver

The most important thing to remember with regards to the construction of this receiver is it MUST be housed in a metal enclosure. Including the power supply. The metal enclosure should reference your power utility ground but ALL other circuitry should reference circuit ground! This includes the power supply ground for +/-, the antenna ground, speaker amp ground, etc. AT NO TIME should the utility ground be connected to or reference circuit ground. By connecting utility ground to the metal enclosure mains related hum drops a thousand fold! P.S. on the speaker amp. It is usually powered by a 9 volt battery but in this application I power it from the power supply "+" to circuit ground. I would advise using single stage op-amps and not duals as the isolation is better. I also use sockets for the op-amps to facilitate easy replacement. If you can not locate the dual 50k linear taper potentiometers I used 100k pots with a 48k fixed value resistor across each section. I will add to this page as necessary but if you wish email me direct at: side7@cox.net