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. There many useful articles describing this type of antenna; so I won’t go into much detail about how it works. More or less it functions as a capacitive E field probe and therefore is very sensitive to EMI. However, if placed outside away from house wiring and provided with a modest local ground reference..the antenna is a good performer.
The 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 a transmission line. This circuit works fine but has some drawback, namely requiring 65mA of current and having a somewhat large input capacitance, which reduces performance with frequency. Ray says:
I decided to use a wide bandwidth op amp to simplify the circuit, reduce current, and provide a little voltage gain. The op amp I chose was one I have used before for RF amplification..the LT1818.
8-6-2021 (August 6, 2021) is the Snakiest day of the year and it’s also this year’s CircuitPython Day! The day highlights all things CircuitPython and Python on Hardware. See you there!
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.