I decided to use a wide bandwidth op amp to simplify the circuit, reduce current, and provide a little voltage gain. This circuit works fine but has some drawback, namely requiring 65mA of current and having a s omewhat large input capacitance, which reduces performance with frequency. The classic circuit uses a JFET source follower and a BJT follower stage to provide impedance transformation of the Hi Z capacitive terminal to a 50 ohm Z drive for transmission line. However, if placed outside away from house wiring and provided with a modest local ground reference.the antenna is a good performer. More or less it functions as a capacitive E field probe and therefore is very sensitive to EMI. There many useful articles describing this type of antenna so I won’t go into much detail about how it works. ![]() I decided to try using a small wide band E field type antenna with my newest receiver design…the Mini SDR and the results have been gratifying.
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