SHORTWAVE RECEIVER

This receiver operates within the frequency range of 8.5 to 11.5 MHz across two distinct bands and exhibits a sensitivity level of less than 1 µV. The NE602 mixer is utilized to feed a 455 kHz intermediate frequency (IF) amplifier, which consists of transistors Q1 and Q2, followed by a detector component D4 and an audio amplifier IC2. Q4 functions as an automatic gain control (AGC) amplifier, with coil data provided in the accompanying table. The local oscillator (LO) is tuned using a varactor diode.

The described receiver is designed to capture signals in the shortwave radio frequency spectrum, specifically targeting frequencies between 8.5 MHz and 11.5 MHz. The sensitivity of under 1 µV allows for the detection of weak signals, making it suitable for various applications, including amateur radio and shortwave listening.

The NE602 mixer plays a critical role in the receiver's architecture by mixing the incoming radio frequency (RF) signals with the local oscillator frequency to produce an intermediate frequency of 455 kHz. This IF frequency is then amplified by the IF amplifier circuit, which employs transistors Q1 and Q2. These transistors are configured to enhance the signal strength while minimizing noise, thereby improving overall performance.

Following the IF amplification stage, the signal is passed to the detector D4, which demodulates the audio signal from the 455 kHz IF. The output of the detector is then fed into the audio amplifier IC2, which amplifies the audio signal to a level suitable for listening through speakers or headphones.

The AGC circuit, implemented using transistor Q4, automatically adjusts the gain of the receiver to maintain a consistent output level despite variations in the input signal strength. This feature is essential for ensuring clear audio output without distortion from strong signals or noise.

The varactor-tuned local oscillator allows for fine-tuning of the receiver to select the desired frequency band. The use of a varactor diode for tuning provides a smooth and stable tuning experience, which is crucial for effective signal reception in the specified frequency range.

Overall, this receiver design demonstrates a well-thought-out approach to shortwave signal reception, combining sensitivity, signal processing, and user-friendly tuning capabilities.This receiver covers 8.5 to 11.5 MHz in two bands and has a sensitivity of under 1 ?V. Nn NE602 mixer feeds a 455-kHz IF amplifier (Q1 and Q2), detector D4, and audio amplifier IC2. Q4 serves as an AGC amplifier coil data is given in the table. The LO is varactor tuned.. 🔗 External reference