Working bands: 80, 40 and 20 meters.
One of the prototypes of the proposed receiver was published in ham radio magazine in 1999. Despite the past years since the publication, the ease of assembly of the receiver, high repeatability, availability of inexpensive components allows this design to remain very popular among beginners and experienced radio Amateurs. Indeed, the ability to listen to three Amateur radio bands looks very attractive. In addition, by adding automatic gain control (AGC) to the receiver, there is a tangible comfort when listening to radio stations. Finally, the size of the PCB allows you to make the receiver lightweight and compact (PCB dimensions 101x49mm).
Direct frequency conversion receiver. The principle of this system is very simple: the heart of the receiver is the SA612 chip – a high-frequency mixer-generator, followed by the integrated circuit of the LM386 low-frequency amplifier. Since the frequency of the local oscillator (or its harmonics) is relatively close to the reception frequency, the difference is only in the low-frequency spectrum. The sum (as any good mixer subtracts and adds at the same time) is in the high frequency spectrum and as a consequence is completely suppressed by the low pass filter. There is no intermediate frequency in the receiver, which greatly simplifies this type of receiver, and the quality remains unusually good. The clarity of the signals, especially in the CW mode.
Recommended for novice and experienced ham radio.