Shortwave MK414-Designed Receiver

The circuit replaces the old circuit that uses ZN414 with a newer MK414 IC but still integrates the same features. It features high quality audio, low current consumption, no alignment and complete stability.

• Shortwave – a term used to describe the radiant energy in the visible, near ultraviolet, and near infrared wavelengths and it operates in the frequency range of 3000 KHz to 30,000 KHz.
• MK484 – a monolithic integrated circuit designed in a TO92 package for use as a one chip radio station, high sensitivity and high quality AM radio is possible with very few external components

Typically, the MK484 has an input impedance of 4M and operates over a frequency range of 150 KHz to 3 MHz with 4 MHz as its maximum. But due to the influence of shortwave broadcast, the receiver can work accordingly with 6 – 7 MHz signal. To obtain high quality performance, the IC’s functioning voltage is controlled by the 10K ohm resistor.

A fixed air space coil and a variable capacitor comprises the regulated circuit. Using an empty with a diameter of 1.5 inches, the coil is wound between 10 and 20 turns of wire. The total length reached around 3 inches because of the gaps created between turns. To receive any AM broadcasts, an external antenna is required which can be connected through the end of the coil or through a series capacitor having a value range of 10pF to 100 pF. The longer the antenna, the better reception would be obtained. A shortwave antenna gives the best clarity and increased range when using a radio to pickup SW and FM signals. For best performance the antenna wire should be positioned as high as possible and fully extended of necessary. It may be supported by a carrying strap. If indoors, it may be attached to some permanent object and if outdoors, a tree branch, fence post or similar support may be used. DO NOT UNDER ANY CIRCUMSTANCES USE A UTILITY POLE AS SUPPORT! Avoid any area where live voltage may be present. In addition to the shock hazard live voltage may cause interference to your shortwave reception.

Some major uses of shortwave radio band include domestic broadcasting, international broadcasting, utility stations, clandestine stations, numbers stations, amateur radio operators, time signal stations, over the horizon radar, and specialty political, religious, and conspiracy theory radio networks. Special features of the circuit include low supply voltage operation making it particularly suited to small hand-held radios.

Source:www.zen22142.zen.co.uk/Circuits/rf/ZN414SW.htm