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Tuned Radio Frequency (TRF) Receiver Circuit diagram. Super heterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver technologies such as the TRF receiver and the regenerative receiver were still widespread. Tuned Radio Frequency (TRF) Receiver Circuit diagram :   Tuned Radio Frequency (TRF) Receiver Circuit Diagram The circuit described here is based on the old technology, but brought up-to-date a The most important part of the circuit is the input stage, where positive feedback is used to achieve good sensitivity and selectivity. The first stage is adjusted so that it is not quite at the point of oscillation. This increases the gain and the selectivity, giving a narrow bandwidth. To achieve this, the potentiometer connected to the drain of the FET must be adjusted very carefully: optimal performance of the receiver depends on its setting. In ideal condit...

Here’s a digital frequency comparator for oscillators that indicates the result through a 7-segment display and a light-emitting diode (LED). When the frequency count of an oscillator is below ‘8,’ the corresponding LED remains turned off. As soon as the count reaches ‘8,’ the LED turns on and the 7-segment display shows ‘8.’ This demo circuit uses two NE555 timers configured as astable free-running oscillators, whose frequencies are to be compared. The circuit of the digital frequency comparator portion comprises two 74LS90 decade counter ICs (IC2 and IC6), two 74LS47 7-segment display driver ICs (IC3 and IC7), 74LS74 set/reset flip-flop (IC4), 74LS00 NAND gate (IC8) and two 7-segment displays (DIS1 and DIS2). The astable free-running oscillators built around the timers are the frequency sources for the corresponding counters. Digital Frequency Comparator Circuit Diagram When power supply to the circuit is switched on, timing capacitor C1 starts charging through resistor R1 and potmet...

Simple phase shift measurement can be done by squaring both the measured and the reference, then compute the difference of the two signals. The accuracy of the circuit shown in the schematic d iagram  below is 1% UP to 2000 cps. This circuit is used in computers and for high speed analog instrumentation. Negative value for zero phase shift is indicated by the zero center DC ammeter, zero for 90′ phase shift and some maximum value for 180′ phase shift.  Phase-Shift Meter for Audio Frequency Signal Circuit Diagram