--- 2024-04-04 ---

A lot of history has been destroyed and cannot be recovered at present. We plan to change and replace it with a new circuit.

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SANYO's LA1600 AM radio IC is a single-chip solution for AM tuning, with few external components required and the ability to receive shortwave signals. Its main specifications include an operating voltage range of 1.8V to 6V, a recommended voltage of 3V, and a 9-pin SIP package. In this article, we will explore how to create a radio that can receive shortwave broadcasts using this IC.

Typically, a "polyvaricon" capacitor is used in the local oscillator section of the circuit. However, using this component can lead to capacitance errors due to wiring capacitance and other factors, potentially leading to instability. Instead, we will use a "varicap diode" to achieve variable frequency, allowing station selection to be done using a volume control and providing more flexibility in the design of the radio case. We recommend centering the receiver around the 9MHz band for best results.

For the coil, we recommend using an FCZ coil from FCZ, a company that also produces equipment for amateur radio. For the varicap diode, we recommend using Toshiba's 1SV101.

To confirm the frequency, a buffer amplifier like the one shown in Figure 3 can be added to the LA1600's 3-pin input. The following frequency relationship applies for reception on the 31m band (9MHz band): 9.4MHz to 10.0MHz.

The specifications for the radio are as follows:

• Reception Method: Single Superheterodyne
• Reception Frequency Range: 31m-BAND (about 9.4MHz to 10MHz)
• Modulation: AM and SSB/CW (SSB/CW can be received by adding optional parts)
• Speaker: Built-in (with external speaker terminal)
• Power: 9V or 12V The IFT (intermediate frequency transformer) used for 455KHz is labeled "black". The antenna used for this project is a long wire approximately 5 meters in length.

By following these guidelines and using the LA1600 IC, you can create a radio capable of receiving AM and shortwave signals with relatively few external components required.