Tuned active antenna (CB8412E)

Found in a 90s Popular Electronics, this circuit allows to select the operating ranges between short waves and VHF. MOSFET is uncommon today.

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Coded Lock with Alarm (CB17377E)
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LM381 Magnetic Head Amplifier (CB25281E)
This circuit was found in the February 1990 issue of Radio Electronics magazine. The circuit uses...
Voltage Comparator Shield (CB4588E)
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...