Zenith TransOceanic Radio Theory of Operation
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Receiver/Scanner Preamp Circuit
The low-cost Mini-Circuits MAR-X series of chips provides a significant advantage for RF builders, featuring inherent 50-ohm input and output impedances essential for RF systems. An MAR-1-based receiver/scanner preamplifier is illustrated. Capacitors Ci and C2 are chip capacitors, with values...
One kind of wireless remote control circuit
The remote control transmitter consists of a DTMF generator and an FM transmitter circuit. A UM91214B phone-specific integrated circuit (IC) is utilized to generate the DTMF signal, with a 3V power supply provided by a 3V zener diode (D1). The...
High Selective Regenerative Shortwave Receiver
The circuit was designed to create a portable and sensitive regenerative receiver suitable for shortwave band listening.
The regenerative receiver circuit is engineered to operate effectively within the shortwave (SW) frequency range, which typically spans from 3 MHz to 30 MHz....
FM Electrocardiogram Monitor with LM331/LM231
V_logic is connected to the power supply Vs and all ground are connected to the negative terminal of the battery. Fout is a square wave of varying frequency with a maximum amplitude of Vs. A voltage divider is needed (200k...
Wireless controlled Door-bell
The controlling range of the wireless doorbell is 100 meters. The transmitter section is designed around an oscillator transistor (BF194B) T2, which is followed by two transistors (BC148) T1 and T3. Transistor T2 generates a specific radio frequency determined by...
Qrp-cw-transceiver
This is a 3-W, single-circuit board, VFO-controlled CW transceiver for 40 or 30 meters, featuring a direct-conversion receiver with audio filtering, Receiver Incremental Tuning (RIT), and speaker-level audio volume. The transmit frequency is generated by Q1 and its associated components...
FM Telephone Bugs
Small telephone bug. It listens to the telephone line on an FM receiver. It is self-powered and has a small part count. Circuit diagram, schematics, electronics project.
The small telephone bug is a compact and efficient device designed to intercept audio...
50MHz 10mW handy transceiver
During a 50MHz SSB-QSO, my friend JE3TXU/1 (Mr. Haraguchi) mentioned that he had created a very compact 50MHz transceiver. I suggested that he should share this information in the Japanese CQ magazine. Additional details can be found in a related...
Shortwave antenna amplifier
This is a wideband shortwave (SW) antenna amplifier. The frequency range spans from 1 to 30 MHz, featuring a medium gain of 15 dB. The input stage utilizes an MPF102 transistor.
The wideband shortwave antenna amplifier is designed to enhance the...