Working of an L-Board Superheterodyne Radio Part-I

The L-Board radio is a popular radio circuit board of the yesteryear. This board has 455 kHz as the intermediate frequency. It was extensively used in radio projects by the hobbyist as well as electronics educational institutions. This radio works well for the medium frequency and high frequency ranges. It uses 6 volts for its operation and it can be used as a mobile radio receiver. This radio helps to organize a frequency spectrum and monitor radio communications that includes broadcast as well as amateur (ham) radio. It was used to build radio receiver for broadcast listening, but it was also used to listen amateur radio communications by incorporating an RF amplifier at the antenna input. During the 80s and 90s, there were regular amateur radio AM communications on the air locally, which can be heard on the 40 meter band.

Technically speaking, the L-board has three sections, RF section, IF section and the audio section. The RF section receives signals from the antenna and mixes with a locally generated oscillator signal using the single transistor oscillator mixer stage. It produces the sum and difference products of the mixed signals. The received IF is then selectively amplified using two stages of intermediate frequency amplifiers. The amplified IF signal is then demodulated using an envelope detector diode. The resultant signal is then filtered using an audio filter and amplified using an audio pre-amplifier. The audio is then applied to a driver transformer to drive a power amplifier using two transistors in transformer coupled class AB operation.


#L-Board Radio
#lboard
#radio
#superheterodyne radio
#lboard superheterodyne radio